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authorTalel Shenhar <talel@amazon.com>2018-10-11 13:20:06 +0200
committerMark Brown <broonie@kernel.org>2018-10-11 16:11:00 +0200
commitd49a30366793210cd64759edcdf7099a2e32efd6 (patch)
tree20b4ab2be8dde23e3c48386c502a49b5e8be3eb1 /drivers/spi/spi-dw.h
parentMerge tag 'qcom-geni-immutable-for-mark-brown' of git://git.kernel.org/pub/sc... (diff)
downloadlinux-d49a30366793210cd64759edcdf7099a2e32efd6.tar.xz
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spi: dw: add compatible for Amazon's Alpine spi controller
This compatible adds the ability for dw spi controller driver to work with the dw spi controller found on Alpine chips. The dw spi controller has an auto-deselect of Chip-Select, in case there is no data inside the Tx FIFO. While working on platforms with Alpine chips, auto-deselect mode causes an issue for some spi devices that can't handle the Chip-Select deselect in the middle of a transaction. It is a normal behavior for a Tx FIFO to be empty in the middle of a transaction, due to busy cpu. In the Alpine chip family an option to change the default behavior was added to the original dw spi controller to prevent this issue of de-asserting Chip-Select once TX FIFO is empty. The change was to allow SW manual control of the Chip-Select. With this change, as long as the Slave Enable Register is asserted, the Chip-Select will be asserted. As a result, it is necessary to deselect the Slave Select Register once the transaction is done. This feature is enabled via a new device compatible string called 'amazon,alpine-dw-apb-ssi'. Once the driver identifies the new compatible string, it enables the hw fixup logic, by writing to a dedicated register found in the IP reserved area and will start manual deselecting the Slave Select Register when the transfer ends. Signed-off-by: Talel Shenhar <talel@amazon.com> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Mark Brown <broonie@kernel.org>
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