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mmc: core: Terminate infinite loop in SD-UHS voltage switch

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This loop intends to retry a max of 10 times, with some implicit
termination based on the SD_{R,}OCR_S18A bit. Unfortunately, the
termination condition depends on the value reported by the SD card
(*rocr), which may or may not correctly reflect what we asked it to do.

Needless to say, it's not wise to rely on the card doing what we expect;
we should at least terminate the loop regardless. So, check both the
input and output values, so we ensure we will terminate regardless of
the SD card behavior.

Note that SDIO learned a similar retry loop in commit 0797e5f145
("mmc: core: Fixup signal voltage switch"), but that used the 'ocr'
result, and so the current pre-terminating condition looks like:

    rocr & ocr & R4_18V_PRESENT

(i.e., it doesn't have the same bug.)

This addresses a number of crash reports seen on ChromeOS that look
like the following:

    ... // lots of repeated: ...
    <4>[13142.846061] mmc1: Skipping voltage switch
    <4>[13143.406087] mmc1: Skipping voltage switch
    <4>[13143.964724] mmc1: Skipping voltage switch
    <4>[13144.526089] mmc1: Skipping voltage switch
    <4>[13145.086088] mmc1: Skipping voltage switch
    <4>[13145.645941] mmc1: Skipping voltage switch
    <3>[13146.153969] INFO: task halt:30352 blocked for more than 122 seconds.
    ...

Fixes: f2119df6b7 ("mmc: sd: add support for signal voltage switch procedure")
Cc: <stable@vger.kernel.org>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220914014010.2076169-1-briannorris@chromium.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Brian Norris 2022-09-13 18:40:10 -07:00 committed by Ulf Hansson
parent 35ca91d133
commit e9233917a7
1 changed files with 2 additions and 1 deletions
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3
drivers/mmc/core/sd.c
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@ -870,7 +870,8 @@ try_again:
* the CCS bit is set as well. We deliberately deviate from the spec in
* regards to this, which allows UHS-I to be supported for SDSC cards.
*/
if (!mmc_host_is_spi(host) && rocr && (*rocr & SD_ROCR_S18A)) {
if (!mmc_host_is_spi(host) && (ocr & SD_OCR_S18R) &&
rocr && (*rocr & SD_ROCR_S18A)) {
err = mmc_set_uhs_voltage(host, pocr);
if (err == -EAGAIN) {
retries--;