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This is a general purpose i2c mux that uses a multiplexer controlled by
the multiplexer subsystem to do the muxing.
The user can select if the mux is to be mux-locked and parent-locked
as described in Documentation/i2c/i2c-topology.
Acked-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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That maintains sanity if it is ever called from some other spot, and
also makes the label names coherent.
Signed-off-by: Peter Rosin <peda@axentia.se>
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It is only prudent to let go of resources that are not used.
Fixes: b3fdd32799d8 ("i2c: mux: Add register-based mux i2c-mux-reg")
Signed-off-by: Peter Rosin <peda@axentia.se>
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git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux
Pull i2c updates from Wilfram Sang:
"I2C has the following updates for you:
- an immutable cross-subsystem branch fixing PMIC access on Intel
Baytrail
- bigger driver updates to the designware, meson, exynos5 drivers
- new i2c_acpi_new_device() function to create devices from ACPI
- struct i2c_driver has now a flag 'disable_i2c_core_irq_mapping' to
allow custom IRQ mapping in case the default does not fit
- mux subsystem centralized error messages in its core
- new driver for ltc4306 i2c mux
- usual set of small updates"
* 'i2c/for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux: (44 commits)
i2c: thunderx: Enable HWMON class probing
i2c: rcar: clarify PM handling with more comments
i2c: rcar: fix resume by always initializing registers before transfer
i2c: tegra: fix spelling mistake: "contoller" -> "controller"
i2c: exynos5: use core helper to get driver data
i2c: exynos5: de-duplicate error logs on clock setup
i2c: exynos5: simplify clock frequency handling
i2c: exynos5: simplify timings calculation
i2c: designware-baytrail: fix potential null pointer dereference on dev
i2c: designware: Get selected speed mode sda-hold-time via ACPI
[media] cx231xx: stop double error reporting
i2c: core: Allow drivers to disable i2c-core irq mapping
i2c: core: Add new i2c_acpi_new_device helper function
i2c: core: Allow getting ACPI info by index
i2c: img-scb: use setup_timer
i2c: i2c-scmi: add a MS HID
i2c: mux: ltc4306: LTC4306 and LTC4305 I2C multiplexer/switch
dt-bindings: i2c: mux: ltc4306: Add dt-bindings for I2C multiplexer/switch
i2c: mux: reg: stop double error reporting
i2c: mux: pinctrl: stop double error reporting
...
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This patch adds support for the Analog Devices / Linear Technology
LTC4306 and LTC4305 4/2 Channel I2C Bus Multiplexer/Switches.
The LTC4306 optionally provides two general purpose input/output pins
(GPIOs) that can be configured as logic inputs, opendrain outputs or
push-pull outputs via the generic GPIOLIB framework.
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Peter Rosin <peda@axentia.se>
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i2c_mux_add_adapter already logs a message on failure.
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
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i2c_mux_add_adapter already logs a message on failure.
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
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i2c_mux_add_adapter already logs a message on failure.
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
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i2c_mux_add_adapter already logs a message on failure.
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
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i2c_mux_add_adapter already logs a message on failure.
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
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i2c_mux_add_adapter already logs a message on failure.
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
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The pca954x i2c mux driver currently implements an irq_chip for handling
interrupts; due to how irq_chip handling is done, it's necessary for the
irq_chip methods to be invoked from hardirq context, even on a a
real-time kernel. Because the spinlock_t type becomes a "sleeping"
spinlock w/ RT kernels, it is not suitable to be used with irq_chips.
A quick audit of the operations under the lock reveal that they do only
minimal, bounded work, and are therefore safe to do under a raw spinlock.
Signed-off-by: Julia Cartwright <julia@ni.com>
Signed-off-by: Peter Rosin <peda@axentia.se>
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The spec for the pca9546 was missing. This chip is the same as the pca9545
except that it lacks interrupt lines. While the i2c_device_id table mapped
the pca9546 to the pca9545 definition the compatible table did not.
Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Peter Rosin <peda@axentia.se>
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In ACPI world any ID should be carefully chosen and registered
officially. The commit bbf9d262a147 seems did a wrong assumption because
PCA is the registered PNP ID for "PHILIPS BU ADD ON CARD". I'm pretty
sure this prefix has nothing to do with the driver in question.
Moreover, newer ACPI specification has a support of _DSD method and
special device IDs to allow drivers be enumerated via compatible string.
The slight change to support this kind of enumeration will be added in
sequential patch against pca954x.c.
Revert the commit bbf9d262a147 for good.
Cc: Tin Huynh <tnhuynh@apm.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Peter Rosin <peda@axentia.se>
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i2c/for-4.11
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Various muxes can aggregate multiple interrupts from each i2c bus.
All of the muxes with interrupt support combine the active low irq lines
using an internal 'and' function and generate a combined active low
output. The muxes do provide the ability to read a control register to
determine which irq is active. By making the mux an irq controller isr
latency can potentially be reduced by reading the status register and
then only calling the registered isr on that bus segment.
As there is no irq masking on the mux irq are disabled until irq_unmask is
called at least once.
Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Peter Rosin <peda@axentia.se>
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The spec for the pca954x was missing. This chip is the same as the pca9540
except that it has interrupt lines. While the i2c_device_id table mapped
the pca9542 to the pca9540 definition the compatible table did not. In
preparation for irq support add the pca9542 definition.
Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Peter Rosin <peda@axentia.se>
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The I2C core always reports a MODALIAS of the form i2c:<foo> even if the
device was registered via OF, this means that exporting the OF device ID
table device aliases in the module is not needed. But in order to change
how the core reports modaliases to user-space, it's better to export it.
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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The I2C core always reports a MODALIAS of the form i2c:<foo> even if the
device was registered via OF, this means that exporting the OF device ID
table device aliases in the module is not needed. But in order to change
how the core reports modaliases to user-space, it's better to export it.
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Remove including <linux/version.h> that don't need it.
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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smbus functions return -ve on error, 0 on success. However,
__i2c_transfer() have a different return signature - -ve on error, or
number of buffers transferred (which may be zero or greater).
The upshot of this is that the sense of the test is reversed when using
the mux on a bus supporting the master_xfer method: we cache the value
and never retry if we fail to transfer any buffers, but if we succeed,
we clear the cached value.
Fix this by making mlxcpld_mux_reg_write() return a -ve error code for
all failure cases, just as was done in commit 7f638c1cb0a1 ("i2c: mux:
pca954x: fix i2c mux selection caching").
This also aligns the implementations of these two muxes in this area.
Signed-off-by: Peter Rosin <peda@axentia.se>
Acked-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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smbus functions return -ve on error, 0 on success. However,
__i2c_transfer() have a different return signature - -ve on error, or
number of buffers transferred (which may be zero or greater.)
The upshot of this is that the sense of the test is reversed when using
the mux on a bus supporting the master_xfer method: we cache the value
and never retry if we fail to transfer any buffers, but if we succeed,
we clear the cached value.
Fix this by making pca954x_reg_write() return a negative error code for
all failure cases.
Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure")
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux
Pull i2c updates from Wolfram Sang:
- the first series of making i2c_device_id optional instead of
mandatory (in favor of alternatives like of_device_id).
This involves adding a new probe callback (probe_new) which removes
some peculiarities I2C had for a long time now. The new probe is
matching the other subsystems now and the old one will be removed
once all users are converted. It is expected to take a while but
there is ongoing interest in that.
- SMBus Host Notify introduced 4.9 got refactored. They are now using
interrupts instead of the alert callback which solves multiple
issues.
- new drivers for iMX LowPower I2C, Mellanox CPLD and its I2C mux
- significant refactoring for bcm2835 driver
- the usual set of driver updates and improvements
* 'i2c/for-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux: (46 commits)
i2c: fsl-lpi2c: read lpi2c fifo size in probe()
i2c: octeon: thunderx: Remove double-check after interrupt
i2c: octeon: thunderx: TWSI software reset in recovery
i2c: cadence: Allow Cadence I2C to be selected for Cadence Xtensa CPUs
i2c: sh_mobile: Add per-Generation fallback bindings
i2c: rcar: Add per-Generation fallback bindings
i2c: imx-lpi2c: add low power i2c bus driver
dt-bindings: i2c: imx-lpi2c: add devicetree bindings
i2c: designware-pcidrv: Add 10bit address feature to medfield/merrifield
i2c: pxa: Add support for the I2C units found in Armada 3700
i2c: pxa: Add definition of fast and high speed modes via the regs layout
dt-bindings: i2c: pxa: Update the documentation for the Armada 3700
i2c: qup: support SMBus block read
i2c: qup: add ACPI support
i2c: designware: Consolidate default functionality bits
i2c: i2c-mux-gpio: update mux with gpiod_set_array_value_cansleep
i2c: mux: pca954x: Add ACPI support for pca954x
i2c: use an IRQ to report Host Notify events, not alert
i2c: i801: remove SMBNTFDDAT reads as they always seem to return 0
i2c: i801: use the BIT() macro for FEATURES_* also
...
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If the gpio controller supports it and the gpio lines are concentrated
to one gpio chip, the mux controller pins will get updated simultaneously.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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This patch enables ACPI support for mux-pca954x driver.
Signed-off-by: Tin Huynh <tnhuynh@apm.com>
Acked-by: Peter Rosin <peda@axentia.se>
[wsa: removed a trailing whitespace]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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This driver allows I2C routing controlled through CPLD select registers on
a wide range of Mellanox systems (CPLD Lattice device).
MUX selection is provided by digital and analog HW. Analog part is not
under SW control.
Digital part is under CPLD control (channel selection/de-selection).
Connectivity schema.
.---. .-------------.
| l | | |-- i2cx1 -- i2cx8
| i |-- i2cn --+--| mlxcpld mux |
| n | | | |-- i2cy1 -- i2cy8
| u | | '-------------'
| x | | |
'---' '---------'
i2c-mux-mlxpcld does not necessarily require i2c-mlxcpld. It can be used
along with another bus driver, and still control i2c routing through CPLD
mux selection, in case the system is equipped with CPLD capable of mux
selection control.
The Kconfig currently controlling compilation of this code is:
drivers/i2c/muxes/Kconfig:config I2C_MUX_MLXCPLD
Signed-off-by: Michael Shych <michaelsh@mellanox.com>
Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Deselect functionality can be ignored for device-trees with
"i2c-mux-idle-disconnect" entries if no platform_data is available.
By enabling the deselect functionality outside the platform_data
block the logic works as it did in previous kernels.
Fixes: 7fcac9807175 ("i2c: i2c-mux-pca954x: convert to use an explicit i2c mux core")
Cc: <stable@vger.kernel.org> # v4.7+
Signed-off-by: Alex Hemme <ahemme@cisco.com>
Signed-off-by: Ziyang Wu <ziywu@cisco.com>
[touched up a few minor issues /peda]
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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We get the following build error from UM Linux after adding
an entry to drivers/iio/gyro/Kconfig that issues "select I2C_MUX":
ERROR: "devm_ioremap_resource"
[drivers/i2c/muxes/i2c-mux-reg.ko] undefined!
ERROR: "of_address_to_resource"
[drivers/i2c/muxes/i2c-mux-reg.ko] undefined!
It appears that the I2C mux core code depends on HAS_IOMEM
for historical reasons, while CONFIG_I2C_MUX_REG does *not*
have a direct dependency on HAS_IOMEM.
This creates a situation where a allyesconfig or allmodconfig
for UM Linux will select I2C_MUX, and will implicitly enable
I2C_MUX_REG as well, and the compilation will fail for the
register driver.
Fix this up by making I2C_MUX_REG depend on HAS_IOMEM and
removing the dependency from I2C_MUX.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Reported-by: Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
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Some drivers like i2c-gpio do not have dedicated pinctrl states. They
broke when error checking for pinctrl was added. Detect them now, and in
their case, simply skip over pinctrl configuration.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux
Pull i2c updates from Wolfram Sang:
"Here is the 4.9 pull request from I2C including:
- centralized error messages when registering to the core
- improved lockdep annotations to prevent false positives
- DT support for muxes, gates, and arbitrators
- bus speeds can now be obtained from ACPI
- i2c-octeon got refactored and now supports ThunderX SoCs, too
- i2c-tegra and i2c-designware got a bigger bunch of updates
- a couple of standard driver fixes and improvements"
* 'i2c/for-4.9' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux: (71 commits)
i2c: axxia: disable clks in case of failure in probe
i2c: octeon: thunderx: Limit register access retries
i2c: uniphier-f: fix misdetection of incomplete STOP condition
gpio: pca953x: variable 'id' was used twice
i2c: i801: Add support for Kaby Lake PCH-H
gpio: pca953x: fix an incorrect lockdep warning
i2c: add a warning to i2c_adapter_depth()
lockdep: make MAX_LOCKDEP_SUBCLASSES unconditionally visible
i2c: export i2c_adapter_depth()
i2c: rk3x: Fix variable 'min_total_ns' unused warning
i2c: rk3x: Fix sparse warning
i2c / ACPI: Do not touch an I2C device if it belongs to another adapter
i2c: octeon: Fix high-level controller status check
i2c: octeon: Avoid sending STOP during recovery
i2c: octeon: Fix set SCL recovery function
i2c: rcar: add support for r8a7796 (R-Car M3-W)
i2c: imx: make bus recovery through pinctrl optional
i2c: meson: add gxbb compatible string
i2c: uniphier-f: set the adapter to master mode when probing
i2c: uniphier-f: avoid WARN_ON() of clk_disable() in failure path
...
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No longer rely on the implicit matching with the i2c device name, use
an explicit compatible string instead.
Keep a direct pointer to the chip description instead of an index into
the chip description array.
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
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No longer rely on the implicit matching with the i2c device name, use
an explicit compatible string instead.
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
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The i2c mux core can then take appropriate action depending on if it is
used for an actual i2c mux, for a gate or for an arbitrator (the last
is the case for these drivers). This adds support for the new clearer
and more compact devicetree bindings that was added recently.
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
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The cached value of the last selected channel prevents retries on the
next call, even on failure to update the selected channel. Fix that.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
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We can't use a static property for all the changesets, so we now create
dynamic ones for each changeset.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Fixes: 50a5ba87690814 ("i2c: mux: demux-pinctrl: add driver")
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Make sure the index to the active channel is invalidated when switching
fails.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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We also need to revert the dynamic OF change, so we get a consistent
state again. Otherwise, we might have two devices enabled e.g. after
pinctrl setup fails.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
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of_address_to_resource return 0 on successful call but
devm_ioremap_resource is called only if it returns non-zero value
Signed-off-by: Lukasz Gemborowski <lukasz.gemborowski@nokia.com>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
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of_match_table was not filled which prevents device to be
instantiated from device tree node.
Signed-off-by: Lukasz Gemborowski <lukasz.gemborowski@nokia.com>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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With a i2c topology like the following
GPIO ---| ------ BAT1
| v /
I2C -----+----------+---- MUX
| \
EEPROM ------ BAT2
there is a locking problem with the GPIO controller since it is a client
on the same i2c bus that it muxes. Transfers to the mux clients (e.g. BAT1)
will lock the whole i2c bus prior to attempting to switch the mux to the
correct i2c segment. In the above case, the GPIO device is an I/O expander
with an i2c interface, and since the GPIO subsystem knows nothing (and
rightfully so) about the lockless needs of the i2c mux code, this results
in a deadlock when the GPIO driver issues i2c transfers to modify the
mux.
So, observing that while it is needed to have the i2c bus locked during the
actual MUX update in order to avoid random garbage on the slave side, it
is not strictly a must to have it locked over the whole sequence of a full
select-transfer-deselect mux client operation. The mux itself needs to be
locked, so transfers to clients behind the mux are serialized, and the mux
needs to be stable during all i2c traffic (otherwise individual mux slave
segments might see garbage, or worse).
Introduce this new locking concept as "mux-locked" muxes, and call the
pre-existing mux locking scheme "parent-locked".
Modify the i2c mux locking so that muxes that are "mux-locked" locks only
the muxes on the parent adapter instead of the whole i2c bus when there is
a transfer to the slave side of the mux. This lock serializes transfers to
the slave side of the muxes on the parent adapter.
Add code to i2c-mux-gpio and i2c-mux-pinctrl that checks if all involved
gpio/pinctrl devices have a parent that is an i2c adapter in the same
adapter tree that is muxed, and request a "mux-locked mux" if that is the
case.
Modify the select-transfer-deselect code for "mux-locked" muxes so
that each of the select-transfer-deselect ops locks the mux parent
adapter individually.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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smatch rightfully says:
drivers/i2c/muxes/i2c-mux-pinctrl.c:175 i2c_mux_pinctrl_probe() warn: inconsistent indenting
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Allocate an explicit i2c mux core to handle parent and child adapters
etc. Update the select/deselect ops to be in terms of the i2c mux core
instead of the child adapter.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Allocate an explicit i2c mux core to handle parent and child adapters
etc. Update the select/deselect ops to be in terms of the i2c mux core
instead of the child adapter.
Add a mask to handle the case where not all child adapters should
cause a mux deselect to happen, now that there is a common deselect op
for all child adapters.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Allocate an explicit i2c mux core to handle parent and child adapters
etc. Update the select/deselect ops to be in terms of the i2c mux core
instead of the child adapter.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Allocate an explicit i2c mux core to handle parent and child adapters
etc. Update the select/deselect ops to be in terms of the i2c mux core
instead of the child adapter.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Allocate an explicit i2c mux core to handle parent and child adapters
etc. Update the select/deselect ops to be in terms of the i2c mux core
instead of the child adapter.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Allocate an explicit i2c mux core to handle parent and child adapters
etc. Update the select/deselect ops to be in terms of the i2c mux core
instead of the child adapter.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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sysfs attributes should use the same format for reads and writes,
rather than pretty-printing on read.
* Make the "cur_master" attribute read back as just the name of the
master
* Expose the list of all masters as a read-only "available_masters"
attribute, using space separators as in similar attributes of other
devices
Also, spell out "cur_master" in full as "current_master".
Fixes: 50a5ba876908 ("i2c: mux: demux-pinctrl: add driver")
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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This driver allows an I2C bus to switch between multiple masters. This
is not hot-switching because connected I2C slaves will be
re-instantiated. It is meant to select the best I2C core at runtime once
the task is known. Example: Prefer i2c-gpio over another I2C core
because of HW errata affecting your use case.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Reading the register (if allowed) after writing is to ensure writing
is completed on a posted bus. The endianness of reading doesn't matter.
Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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