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authorDmitry Torokhov <dmitry.torokhov@gmail.com>2021-03-25 19:46:10 +0100
committerDmitry Torokhov <dmitry.torokhov@gmail.com>2021-03-25 19:46:10 +0100
commit5acac83bf2e42f51ab9fd315d657798754bf0bb8 (patch)
tree564be60664226649f00798cc3afb72d72d0ed24d /Documentation/driver-api/media/camera-sensor.rst
parentInput: cyttsp - verbose error on soft reset (diff)
parentLinux 5.12-rc4 (diff)
downloadlinux-5acac83bf2e42f51ab9fd315d657798754bf0bb8.tar.xz
linux-5acac83bf2e42f51ab9fd315d657798754bf0bb8.zip
Merge tag 'v5.12-rc4' into next
Sync up with the mainline to bring in newest APIs.
Diffstat (limited to 'Documentation/driver-api/media/camera-sensor.rst')
-rw-r--r--Documentation/driver-api/media/camera-sensor.rst20
1 files changed, 19 insertions, 1 deletions
diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst
index ffb0cad8137a..3fc378b3b269 100644
--- a/Documentation/driver-api/media/camera-sensor.rst
+++ b/Documentation/driver-api/media/camera-sensor.rst
@@ -15,7 +15,7 @@ Camera sensors have an internal clock tree including a PLL and a number of
divisors. The clock tree is generally configured by the driver based on a few
input parameters that are specific to the hardware:: the external clock frequency
and the link frequency. The two parameters generally are obtained from system
-firmware. No other frequencies should be used in any circumstances.
+firmware. **No other frequencies should be used in any circumstances.**
The reason why the clock frequencies are so important is that the clock signals
come out of the SoC, and in many cases a specific frequency is designed to be
@@ -23,6 +23,24 @@ used in the system. Using another frequency may cause harmful effects
elsewhere. Therefore only the pre-determined frequencies are configurable by the
user.
+ACPI
+~~~~
+
+Read the "clock-frequency" _DSD property to denote the frequency. The driver can
+rely on this frequency being used.
+
+Devicetree
+~~~~~~~~~~
+
+The currently preferred way to achieve this is using "assigned-clock-rates"
+property. See Documentation/devicetree/bindings/clock/clock-bindings.txt for
+more information. The driver then gets the frequency using clk_get_rate().
+
+This approach has the drawback that there's no guarantee that the frequency
+hasn't been modified directly or indirectly by another driver, or supported by
+the board's clock tree to begin with. Changes to the Common Clock Framework API
+are required to ensure reliability.
+
Frame size
----------