On Tue, 23 Feb 2021 at 14:42, Adrian Hunter [off-list ref] wrote:

On 23/02/21 1:54 pm, Ulf Hansson wrote:

quoted

On Tue, 23 Feb 2021 at 12:19, Paul Fertser [off-list ref] wrote:

quoted

Hello Adrian,

On Tue, Feb 23, 2021 at 01:01:09PM +0200, Adrian Hunter wrote:

quoted

On 23/02/21 11:32 am, Paul Fertser wrote:

quoted

Hello Ulf,

On Tue, Feb 23, 2021 at 10:23:28AM +0100, Ulf Hansson wrote:

quoted

quoted

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index f5dedb7f9b27..9adf735391fa 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c

@@ -426,8 +426,7 @@ static int mmc_decode_ext_csd(struct mmc_card *card, u8 *ext_csd)
                /* EXT_CSD value is in units of 10ms, but we store in ms */
                card->ext_csd.part_time = 10 * ext_csd[EXT_CSD_PART_SWITCH_TIME];
                /* Some eMMC set the value too low so set a minimum */
-               if (card->ext_csd.part_time &&
-                   card->ext_csd.part_time < MMC_MIN_PART_SWITCH_TIME)
+               if (card->ext_csd.part_time < MMC_MIN_PART_SWITCH_TIME)
                        card->ext_csd.part_time = MMC_MIN_PART_SWITCH_TIME;

                /* Sleep / awake timeout in 100ns units */

I do not see any more warnings on my system.

That looks like the correct fix to the problem. Do you want to send a
proper patch that I can pick up or do you prefer if help to do it?

I've sent this as a diff precisely because 1c447116d017 was so
explicit about special-casing zero ext_csd timeout value, so I thought
probably Adrian can provide the rationale for that. I'd prefer to wait
for his feedback before sending a formal patch. Does this make sense?

Zero means indefinite.  Might be safer to use a higher value than
MMC_MIN_PART_SWITCH_TIME for that case.  The maximum GENERIC_CMD6_TIME is
2550 ms.

Thanks for the clarification! I would guess that most likely than not
when whoever defines that value to be zero it means "I do not
care/know" rather than "the timeout must be set to more than 2550 ms,
too bad 8 bits are not enough to represent that". I'd say setting it
to DEFAULT_CMD6_TIMEOUT_MS should be safe enough since it worked
before.

Hmm.

The DEFAULT_CMD6_TIMEOUT_MS is intended to override the
ext_csd->generic_cmd6_time, in case it's not defined in the register.

Perhaps it's reasonable to think that eMMC vendors specify the
GENERIC_CMD6_TIME, but may skip to specify other timeouts, like the
PARTITION_SWITCH_TIME. In that case, should we use the specified
GENERIC_CMD6_TIME, rather than always default to
DEFAULT_CMD6_TIMEOUT_MS?

Sounds reasonable, but perhaps still enforce a minimum, for some of the same
reasons as commit 1c447116d017 ?
e.g.

        if (!card->ext_csd.part_time)
                card->ext_csd.part_time = card->ext_csd.generic_cmd6_time;
        if (card->ext_csd.part_time < MMC_MIN_PART_SWITCH_TIME)
                card->ext_csd.part_time = MMC_MIN_PART_SWITCH_TIME;

Makes perfect sense to me!

Kind regards
Uffe