On Wed, 13 Feb 2019 at 10:07, Chaotian Jing <chaotian.jing@xxxxxxxxxxxx> wrote:
>
> mmc_hs400_to_hs200() begins with the card and host in HS400 mode.
> Therefore, any commands sent to the card should use HS400 timing.
> reduce clock frequency to 50Mhz but without host timming change
> may cause CMD6 response CRC error. because host still running at
> hs400 mode, and it's hard to find a suitable setting for all eMMC
> cards when clock frequency reduced to 50Mhz but card & host still
> in hs400 mode.
> this patch refers to mmc_select_hs400(), make the reduce clock frequency
> after card timing change.
>
> Signed-off-by: Chaotian Jing <chaotian.jing@xxxxxxxxxxxx>
> Fixes: ef3d232245ab ("mmc: mmc: Relax checking for switch errors after HS200 switch")
> ---
> drivers/mmc/core/mmc.c | 29 +++++++++++++++++++++++------
> 1 file changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 09c688f..00adc2d 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1239,20 +1239,37 @@ int mmc_hs400_to_hs200(struct mmc_card *card)
> int err;
> u8 val;
>
> - /* Reduce frequency to HS */
> - max_dtr = card->ext_csd.hs_max_dtr;
> - mmc_set_clock(host, max_dtr);
> -
> /* Switch HS400 to HS DDR */
> val = EXT_CSD_TIMING_HS;
> err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING,
> val, card->ext_csd.generic_cmd6_time, 0,
> true, false, true);
> - if (err)
> - goto out_err;
> + /*
> + * as we are on the way to do re-tune, so if the CMD6 got response CRC
> + * error, do not treat it as error.
> + */
> + if (err) {
> + if (err == -EILSEQ) {
> + /*
> + * card will busy after sending out response and host
> + * driver may not wait busy de-assert when get
> + * response CRC error. so just wait enough time to
> + * ensure card leave busy state.
> + */
> + mmc_delay(card->ext_csd.generic_cmd6_time);
> + pr_debug("%s: %s switch to HS got CRC error\n",
> + mmc_hostname(host), __func__);
> + } else {
> + goto out_err;
> + }
> + }
>
> mmc_set_timing(host, MMC_TIMING_MMC_DDR52);
>
> + /* Reduce frequency to HS */
> + max_dtr = card->ext_csd.hs_max_dtr;
> + mmc_set_clock(host, max_dtr);
> +
What Adrian suggested was to not to move this part, but instead, only
allow CRC errors from the CMD6 as above.
I guess it didn't work for you?
> err = mmc_switch_status(card);
> if (err)
> goto out_err;
> --
> 1.8.1.1.dirty
>
Kind regards
Uffe
