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authorBrian Norris <briannorris@chromium.org>2018-05-22 17:23:10 -0700
committerLee Jones <lee.jones@linaro.org>2018-05-23 06:59:00 +0100
commit11799564fc7eedff50801950090773928f867996 (patch)
tree900623616bd4d55b38798be4325376e916649b57 /drivers/fpga
parent771c577c23bac90597c685971d7297ea00f99d11 (diff)
downloadlinux-11799564fc7eedff50801950090773928f867996.tar.bz2
mfd: cros_ec: Retry commands when EC is known to be busy
Commit 001dde9400d5 ("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 001dde9400d5 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 001dde9400d5, this resolves bugs like the following: 1. EC_CMD_FLASH_ERASE now works again (with commit 001dde9400d5, we would abort the first time we saw EC_SPI_PAST_END) 2. Before commit 001dde9400d5, 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: 001dde9400d5 ("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>
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