Re: [PATCH 3/3] mmc: core: Default to generic_cmd6_time as timeout in __mmc_switch()

Paul Fertser
2021-02-23T11:20:34Z

Hello Adrian,

On Tue, Feb 23, 2021 at 01:01:09PM +0200, Adrian Hunter wrote:
> On 23/02/21 11:32 am, Paul Fertser wrote:
> > Hello Ulf,
> >
> > On Tue, Feb 23, 2021 at 10:23:28AM +0100, Ulf Hansson wrote:
> >>> 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.

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