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Brian Norris 11799564fc mfd: cros_ec: Retry commands when EC is known to be busy 
Commit 001dde9400 ("mfd: cros ec: spi: Fix "in progress" error
signaling") pointed out some bad code, but its analysis and conclusion
was not 100% correct.

It *is* correct that we should not propagate result==EC_RES_IN_PROGRESS
for transport errors, because this has a special meaning -- that we
should follow up with EC_CMD_GET_COMMS_STATUS until the EC is no longer
busy. This is definitely the wrong thing for many commands, because
among other problems, EC_CMD_GET_COMMS_STATUS doesn't actually retrieve
any RX data from the EC, so commands that expected some data back will
instead start processing junk.

For such commands, the right answer is to either propagate the error
(and return that error to the caller) or resend the original command
(*not* EC_CMD_GET_COMMS_STATUS).

Unfortunately, commit 001dde9400 forgets a crucial point: that for
some long-running operations, the EC physically cannot respond to
commands any more. For example, with EC_CMD_FLASH_ERASE, the EC may be
re-flashing its own code regions, so it can't respond to SPI interrupts.
Instead, the EC prepares us ahead of time for being busy for a "long"
time, and fills its hardware buffer with EC_SPI_PAST_END. Thus, we
expect to see several "transport" errors (or, messages filled with
EC_SPI_PAST_END). So we should really translate that to a retryable
error (-EAGAIN) and continue sending EC_CMD_GET_COMMS_STATUS until we
get a ready status.

IOW, it is actually important to treat some of these "junk" values as
retryable errors.

Together with commit 001dde9400, this resolves bugs like the
following:

1. EC_CMD_FLASH_ERASE now works again (with commit 001dde9400, we
   would abort the first time we saw EC_SPI_PAST_END)
2. Before commit 001dde9400, transport errors (e.g.,
   EC_SPI_RX_BAD_DATA) seen in other commands (e.g.,
   EC_CMD_RTC_GET_VALUE) used to yield junk data in the RX buffer; they
   will now yield -EAGAIN return values, and tools like 'hwclock' will
   simply fail instead of retrieving and re-programming undefined time
   values

Fixes: 001dde9400 ("mfd: cros ec: spi: Fix "in progress" error signaling")
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
2018-05-23 06:59:00 +01:00
arch Merge branch 'parisc-4.17-5' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux 2018-05-20 12:44:07 -07:00
block blk-mq: fix sysfs inflight counter 2018-04-26 09:02:01 -06:00
certs certs/blacklist_nohashes.c: fix const confusion in certs blacklist 2018-02-21 15:35:43 -08:00
crypto crypto: drbg - set freed buffers to NULL 2018-04-21 00:57:00 +08:00
Documentation ARM: SoC fixes for 4.17-rc 2018-05-19 19:56:15 -07:00
drivers mfd: cros_ec: Retry commands when EC is known to be busy 2018-05-23 06:59:00 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs for-4.17-rc5-tag 2018-05-20 12:04:27 -07:00
include Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-05-20 10:43:27 -07:00
init sched/fair: Fix documentation file path 2018-05-18 09:05:28 +02:00
ipc ipc/shm: fix use-after-free of shm file via remap_file_pages() 2018-04-13 17:10:27 -07:00
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-05-20 11:25:54 -07:00
lib radix tree: fix multi-order iteration race 2018-05-18 17:17:12 -07:00
LICENSES LICENSES: Add MPL-1.1 license 2018-01-06 10:59:44 -07:00
mm mmap: relax file size limit for regular files 2018-05-19 09:29:11 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-05-11 14:14:46 -07:00
samples x86/cpufeature: Guard asm_volatile_goto usage for BPF compilation 2018-05-13 21:49:14 +02:00
scripts scripts/faddr2line: fix error when addr2line output contains discriminator 2018-05-11 17:28:45 -07:00
security selinux/stable-4.17 PR 20180516 2018-05-17 10:02:19 -07:00
sound ALSA: usb-audio: Use Class Specific EP for UAC3 devices. 2018-05-15 07:29:10 +02:00
tools Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-05-20 11:28:32 -07:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt KVM: arm/arm64: VGIC/ITS save/restore: protect kvm_read_guest() calls 2018-05-15 13:36:53 +02:00
.clang-format clang-format: add configuration file 2018-04-11 10:28:35 -07:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap Merge candidates for 4.17 merge window 2018-04-06 17:35:43 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS/CREDITS: Drop METAG ARCHITECTURE 2018-03-05 16:34:24 +00:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS dmaengine fix for 4.17-rc6 2018-05-19 09:54:02 -07:00
Makefile Linux 4.17-rc6 2018-05-20 15:31:38 -07:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.