On 18/11/16 16:37, Ulf Hansson wrote:
> On 18 November 2016 at 14:35, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>> On 16/11/16 12:51, Ulf Hansson wrote:
>>> In cases when the mmc host doesn't support HW busy detection, polling for
>>> busy by using CMD13 is beneficial. The reasons have already been explained
>>> in earlier change logs.
>>>
>>> Moreover, when polling with CMD13 during bus timing changes, we should
>>> retry instead of fail when we get CRC errors.
>>>
>>> Switching to HS400ES includes several steps, where each step changes the
>>> bus speed timing. Let's improve the behaviour during these sequences, by
>>> allowing CMD13 polling for each of the step. Let's also make sure the CMD13
>>> polling becomes retried, while receiving a CRC error.
>>>
>>> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>>> ---
>>> drivers/mmc/core/mmc.c | 35 +++++++++++------------------------
>>> 1 file changed, 11 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>>> index 24b9e72..b6f0035 100644
>>> --- a/drivers/mmc/core/mmc.c
>>> +++ b/drivers/mmc/core/mmc.c
>>> @@ -1227,31 +1227,24 @@ static int mmc_select_hs400es(struct mmc_card *card)
>>> goto out_err;
>>>
>>> /* Switch card to HS mode */
>>> - err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>>> - EXT_CSD_HS_TIMING, EXT_CSD_TIMING_HS,
>>> - card->ext_csd.generic_cmd6_time, 0,
>>> - true, false, true);
>>> + err = mmc_select_hs(card);
>>> if (err) {
>>> pr_err("%s: switch to hs for hs400es failed, err:%d\n",
>>> mmc_hostname(host), err);
>>> goto out_err;
>>> }
>>>
>>> - mmc_set_timing(host, MMC_TIMING_MMC_HS);
>>> - err = mmc_switch_status(card);
>>> - if (err)
>>> - goto out_err;
>>> -
>>> mmc_set_clock(host, card->ext_csd.hs_max_dtr);
>>>
>>> - /* Switch card to DDR with strobe bit */
>>> + /* Switch card to HS DDR with strobe bit */
>>> val = EXT_CSD_DDR_BUS_WIDTH_8 | EXT_CSD_BUS_WIDTH_STROBE;
>>> - err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>>> - EXT_CSD_BUS_WIDTH,
>>> - val,
>>> - card->ext_csd.generic_cmd6_time);
>>> + err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>>> + EXT_CSD_BUS_WIDTH, val,
>>> + card->ext_csd.generic_cmd6_time,
>>> + MMC_TIMING_MMC_DDR52,
>>> + true, true, true);
>>> if (err) {
>>> - pr_err("%s: switch to bus width for hs400es failed, err:%d\n",
>>> + pr_err("%s: switch to hs ddr for hs400es failed, err:%d\n",
>>> mmc_hostname(host), err);
>>> goto out_err;
>>> }
>>> @@ -1261,26 +1254,20 @@ static int mmc_select_hs400es(struct mmc_card *card)
>>> card->drive_strength << EXT_CSD_DRV_STR_SHIFT;
>>> err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>>> EXT_CSD_HS_TIMING, val,
>>> - card->ext_csd.generic_cmd6_time, 0,
>>> - true, false, true);
>>> + card->ext_csd.generic_cmd6_time,
>>> + MMC_TIMING_MMC_HS400,
>>> + true, true, true);
>>
>> This could be a problem because the CMD13 is being sent to a card in HS400
>> enhanced strobe mode but we haven't enabled enhanced strobe on the host
>> controller yet. Previously mmc_switch_status(card) was below
>> host->ops->hs400_enhanced_strobe().
>>
>
> Yes, more or less the same reasons as before. We need the "tuning" (in
> this case the "strobing") to be done before validating the switch
> status.
>
> Although, the change a little further above, when switching to HS DDR
> in the intermediate step - that should be fine, don't you think?
Yes
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