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Serge Semin 9aea644ca1
spi: dw: Fix native CS being unset 
Commit 6e0a32d6f3 ("spi: dw: Fix default polarity of native
chipselect") attempted to fix the problem when GPIO active-high
chip-select is utilized to communicate with some SPI slave. It fixed
the problem, but broke the normal native CS support. At the same time
the reversion commit ada9e3fcc1 ("spi: dw: Correct handling of native
chipselect") didn't solve the problem either, since it just inverted
the set_cs() polarity perception without taking into account that
CS-high might be applicable. Here is what is done to finally fix the
problem.

DW SPI controller demands any native CS being set in order to proceed
with data transfer. So in order to activate the SPI communications we
must set any bit in the Slave Select DW SPI controller register no
matter whether the platform requests the GPIO- or native CS. Preferably
it should be the bit corresponding to the SPI slave CS number. But
currently the dw_spi_set_cs() method activates the chip-select
only if the second argument is false. Since the second argument of the
set_cs callback is expected to be a boolean with "is-high" semantics
(actual chip-select pin state value), the bit in the DW SPI Slave
Select register will be set only if SPI core requests the driver
to set the CS in the low state. So this will work for active-low
GPIO-based CS case, and won't work for active-high CS setting
the bit when SPI core actually needs to deactivate the CS.

This commit fixes the problem for all described cases. So no matter
whether an SPI slave needs GPIO- or native-based CS with active-high
or low signal the corresponding bit will be set in SER.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Fixes: ada9e3fcc1 ("spi: dw: Correct handling of native chipselect")
Fixes: 6e0a32d6f3 ("spi: dw: Fix default polarity of native chipselect")
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>

Link: https://lore.kernel.org/r/20200515104758.6934-5-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
2020-05-15 18:29:15 +01:00
arch s390 fixes for 5.7-rc3 2020-04-26 10:58:49 -07:00
block blk-iocost: Fix error on iocost_ioc_vrate_adj 2020-04-21 09:49:36 -06:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto x86: update AS_* macros to binutils >=2.23, supporting ADX and AVX2 2020-04-09 00:12:48 +09:00
Documentation spi: Convert UniPhier SPI controller to json-schema 2020-05-12 11:16:54 +01:00
drivers spi: dw: Fix native CS being unset 2020-05-15 18:29:15 +01:00
fs Five cifs/smb3 fixes, 3 for DFS, one for stable 2020-04-26 11:44:17 -07:00
include Staging/IIO driver fixes for 5.7-rc3 2020-04-26 11:12:30 -07:00
init Kbuild updates for v5.7 (2nd) 2020-04-11 09:46:12 -07:00
ipc ipc/util.c: sysvipc_find_ipc() should increase position index 2020-04-10 15:36:22 -07:00
kernel Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-04-25 12:25:32 -07:00
lib lib/mpi: Fix building for powerpc with clang 2020-04-24 13:14:59 +10:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm: check that mm is still valid in madvise() 2020-04-24 13:28:03 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-04-24 19:17:30 -07:00
samples vmalloc: fix remap_vmalloc_range() bounds checks 2020-04-21 11:11:56 -07:00
scripts Kbuild fixes for v5.7 2020-04-24 10:39:32 -07:00
security selinux/stable-5.7 PR 20200416 2020-04-16 10:45:47 -07:00
sound sound fixes for 5.7-rc3 2020-04-24 10:27:43 -07:00
tools Linux 5.7-rc3 2020-04-27 15:04:50 +01:00
usr kbuild: fix comment about missing include guard detection 2020-04-11 12:09:48 +09:00
virt KVM: Pass kvm_init()'s opaque param to additional arch funcs 2020-03-31 10:48:03 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2020-04-18 13:49:33 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
.mailmap mailmap: Add Sedat Dilek (replacement for expired email address) 2020-04-11 09:28:34 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Hand MIPS over to Thomas 2020-02-24 22:43:18 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS spi: spi-amd: Add AMD SPI controller driver support 2020-04-27 16:38:32 +01:00
Makefile Linux 5.7-rc3 2020-04-26 13:51:02 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.