Re: [PATCH v3] mmc: Change the max discard sectors and erase response if mmc host supports busy signalling

[Baolin Wang]

On 25 July 2016 at 17:26, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> On 25 July 2016 at 10:48, Baolin Wang <baolin.wang@xxxxxxxxxx> wrote:
>> When mmc host HW supports busy signalling (using R1B as response), We
>> shouldn't use 'host->max_busy_timeout' as the limitation when deciding
>> the max discard sectors that we tell the generic BLOCK layer about.
>> Instead, we should pick one preferred erase size as the max discard
>> sectors.
>>
>> If the host controller supports busy signalling and the timeout for
>> the erase operation does not exceed the max_busy_timeout, we should
>> use R1B response. Or we need to prevent the host from doing hw busy
>> detection, which is done by converting to a R1 response instead.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
>
> Thanks, applied for next! I took the liberty to update the change-log
> a bit to clarify things!
>
> Thanks a lot for working on this long outstanding problem!
>
> In the next step I plan to remove the MMC_CAP_ERASE and instead enable
> it by default, although let's leave that for v4.9.

OK. I will investigate that and send patch to fix that. Thanks for
your useful suggetion.:)

>> ---
>> Changes since v2:
>>   - Remove the 'MMC_CAP_WAIT_WHILE_BUSY' flag checking when deciding
>>   if we can use R1B response.
>>   - Avoid polling CMD13 when using R1B response.
>>   - Use earlier calculated erase timeout as the polling time.
>>
>> Changes since v1:
>>   - Remove the 'MMC_CAP_WAIT_WHILE_BUSY' flag checking when deciding
>>     the max discard sectors.
>> ---
>>  drivers/mmc/core/core.c |   60 +++++++++++++++++++++++++++++++++++++++--------
>>  1 file changed, 50 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 8b4dfd4..b4c08d1a 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -2060,7 +2060,8 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from,
>>                         unsigned int to, unsigned int arg)
>>  {
>>         struct mmc_command cmd = {0};
>> -       unsigned int qty = 0;
>> +       unsigned int qty = 0, busy_timeout = 0;
>> +       bool use_r1b_resp = false;
>>         unsigned long timeout;
>>         int err;
>>
>> @@ -2128,8 +2129,22 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from,
>>         memset(&cmd, 0, sizeof(struct mmc_command));
>>         cmd.opcode = MMC_ERASE;
>>         cmd.arg = arg;
>> -       cmd.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
>> -       cmd.busy_timeout = mmc_erase_timeout(card, arg, qty);
>> +       busy_timeout = mmc_erase_timeout(card, arg, qty);
>> +       /*
>> +        * If the host controller supports busy signalling and the timeout for
>> +        * the erase operation does not exceed the max_busy_timeout, we should
>> +        * use R1B response. Or we need to prevent the host from doing hw busy
>> +        * detection, which is done by converting to a R1 response instead.
>> +        */
>> +       if (card->host->max_busy_timeout &&
>> +           busy_timeout > card->host->max_busy_timeout) {
>> +               cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_AC;
>> +       } else {
>> +               cmd.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
>> +               cmd.busy_timeout = busy_timeout;
>> +               use_r1b_resp = true;
>> +       }
>> +
>>         err = mmc_wait_for_cmd(card->host, &cmd, 0);
>>         if (err) {
>>                 pr_err("mmc_erase: erase error %d, status %#x\n",
>> @@ -2141,7 +2156,14 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from,
>>         if (mmc_host_is_spi(card->host))
>>                 goto out;
>>
>> -       timeout = jiffies + msecs_to_jiffies(MMC_CORE_TIMEOUT_MS);
>> +       /*
>> +        * In case of when R1B + MMC_CAP_WAIT_WHILE_BUSY is used, the polling
>> +        * shall be avoided.
>> +        */
>> +       if ((card->host->caps & MMC_CAP_WAIT_WHILE_BUSY) && use_r1b_resp)
>> +               goto out;
>> +
>> +       timeout = jiffies + msecs_to_jiffies(busy_timeout);
>>         do {
>>                 memset(&cmd, 0, sizeof(struct mmc_command));
>>                 cmd.opcode = MMC_SEND_STATUS;
>> @@ -2321,23 +2343,41 @@ static unsigned int mmc_do_calc_max_discard(struct mmc_card *card,
>>                                             unsigned int arg)
>>  {
>>         struct mmc_host *host = card->host;
>> -       unsigned int max_discard, x, y, qty = 0, max_qty, timeout;
>> +       unsigned int max_discard, x, y, qty = 0, max_qty, min_qty, timeout;
>>         unsigned int last_timeout = 0;
>>
>> -       if (card->erase_shift)
>> +       if (card->erase_shift) {
>>                 max_qty = UINT_MAX >> card->erase_shift;
>> -       else if (mmc_card_sd(card))
>> +               min_qty = card->pref_erase >> card->erase_shift;
>> +       } else if (mmc_card_sd(card)) {
>>                 max_qty = UINT_MAX;
>> -       else
>> +               min_qty = card->pref_erase;
>> +       } else {
>>                 max_qty = UINT_MAX / card->erase_size;
>> +               min_qty = card->pref_erase / card->erase_size;
>> +       }
>>
>> -       /* Find the largest qty with an OK timeout */
>> +       /*
>> +        * We should not only use 'host->max_busy_timeout' as the limitation
>> +        * when deciding the max discard sectors. We should set a balance value
>> +        * to improve the erase speed, and it can not get too long timeout at
>> +        * the same time.
>> +        *
>> +        * Here we set 'card->pref_erase' as the minimal discard sectors no
>> +        * matter what size of 'host->max_busy_timeout', but if the
>> +        * 'host->max_busy_timeout' is large enough for more discard sectors,
>> +        * then we can continue to increase the max discard sectors until we
>> +        * get a balance value.
>> +        */
>>         do {
>>                 y = 0;
>>                 for (x = 1; x && x <= max_qty && max_qty - x >= qty; x <<= 1) {
>>                         timeout = mmc_erase_timeout(card, arg, qty + x);
>> -                       if (timeout > host->max_busy_timeout)
>> +
>> +                       if (qty + x > min_qty &&
>> +                           timeout > host->max_busy_timeout)
>>                                 break;
>> +
>>                         if (timeout < last_timeout)
>>                                 break;
>>                         last_timeout = timeout;
>> --
>> 1.7.9.5
>>



-- 
Baolin.wang
Best Regards