Re: [PATCH v1] mmc: core: check R1_STATUS for erase/trim/discard

[Adrian Hunter]

On 25/04/24 19:18, Ulf Hansson wrote:
> + Wolfram, Adrian (to see if they have some input)
> 
> On Tue, 23 Apr 2024 at 22:02, Kamal Dasu <kamal.dasu@xxxxxxxxxxxx> wrote:
>>
>> When erase/trim/discard completion was converted to mmc_poll_for_busy(),
>> optional ->card_busy() host ops support was added. sdhci card->busy()
>> could return busy for long periods to cause mmc_do_erase() to block during
>> discard operation as shown below during mkfs.f2fs :
>>
>> Info: [/dev/mmcblk1p9] Discarding device
>> [   39.597258] sysrq: Show Blocked State
>> [   39.601183] task:mkfs.f2fs       state:D stack:0     pid:1561  tgid:1561  ppid:1542   flags:0x0000000d
>> [   39.610609] Call trace:
>> [   39.613098]  __switch_to+0xd8/0xf4
>> [   39.616582]  __schedule+0x440/0x4f4
>> [   39.620137]  schedule+0x2c/0x48
>> [   39.623341]  schedule_hrtimeout_range_clock+0xe0/0x114
>> [   39.628562]  schedule_hrtimeout_range+0x10/0x18
>> [   39.633169]  usleep_range_state+0x5c/0x90
>> [   39.637253]  __mmc_poll_for_busy+0xec/0x128
>> [   39.641514]  mmc_poll_for_busy+0x48/0x70
>> [   39.645511]  mmc_do_erase+0x1ec/0x210
>> [   39.649237]  mmc_erase+0x1b4/0x1d4
>> [   39.652701]  mmc_blk_mq_issue_rq+0x35c/0x6ac
>> [   39.657037]  mmc_mq_queue_rq+0x18c/0x214
>> [   39.661022]  blk_mq_dispatch_rq_list+0x3a8/0x528
>> [   39.665722]  __blk_mq_sched_dispatch_requests+0x3a0/0x4ac
>> [   39.671198]  blk_mq_sched_dispatch_requests+0x28/0x5c
>> [   39.676322]  blk_mq_run_hw_queue+0x11c/0x12c
>> [   39.680668]  blk_mq_flush_plug_list+0x200/0x33c
>> [   39.685278]  blk_add_rq_to_plug+0x68/0xd8
>> [   39.689365]  blk_mq_submit_bio+0x3a4/0x458
>> [   39.693539]  __submit_bio+0x1c/0x80
>> [   39.697096]  submit_bio_noacct_nocheck+0x94/0x174
>> [   39.701875]  submit_bio_noacct+0x1b0/0x22c
>> [   39.706042]  submit_bio+0xac/0xe8
>> [   39.709424]  blk_next_bio+0x4c/0x5c
>> [   39.712973]  blkdev_issue_secure_erase+0x118/0x170
>> [   39.717835]  blkdev_common_ioctl+0x374/0x728
>> [   39.722175]  blkdev_ioctl+0x8c/0x2b0
>> [   39.725816]  vfs_ioctl+0x24/0x40
>> [   39.729117]  __arm64_sys_ioctl+0x5c/0x8c
>> [   39.733114]  invoke_syscall+0x68/0xec
>> [   39.736839]  el0_svc_common.constprop.0+0x70/0xd8
>> [   39.741609]  do_el0_svc+0x18/0x20
>> [   39.744981]  el0_svc+0x68/0x94
>> [   39.748107]  el0t_64_sync_handler+0x88/0x124
>> [   39.752455]  el0t_64_sync+0x168/0x16c
> 
> Thanks for the detailed log!
> 
>>
>> Fix skips the card->busy() and uses MMC_SEND_STATUS and R1_STATUS
>> check for MMC_ERASE_BUSY busy_cmd case in the mmc_busy_cb() function.
>>
>> Fixes: 0d84c3e6a5b2 ("mmc: core: Convert to mmc_poll_for_busy() for erase/trim/discard")
>> Signed-off-by: Kamal Dasu <kamal.dasu@xxxxxxxxxxxx>
>> ---
>>  drivers/mmc/core/mmc_ops.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
>> index 3b3adbddf664..603fbd78c342 100644
>> --- a/drivers/mmc/core/mmc_ops.c
>> +++ b/drivers/mmc/core/mmc_ops.c
>> @@ -464,7 +464,8 @@ static int mmc_busy_cb(void *cb_data, bool *busy)
>>         u32 status = 0;
>>         int err;
>>
>> -       if (data->busy_cmd != MMC_BUSY_IO && host->ops->card_busy) {
>> +       if (data->busy_cmd != MMC_BUSY_IO &&
>> +           data->busy_cmd != MMC_BUSY_ERASE && host->ops->card_busy) {
>>                 *busy = host->ops->card_busy(host);
>>                 return 0;
>>         }
> 
> So it seems like the ->card_busy() callback is broken in for your mmc
> host-driver and platform. Can you perhaps provide the information
> about what HW/driver you are using?
> 
> The point with using the ->card_busy() callback, is to avoid sending
> the CMD13. Ideally it should be cheaper/faster and in most cases it
> translates to a read of a register. For larger erases, we would
> probably end up sending the CMD13 periodically every 32-64 ms, which
> shouldn't be a problem. However, for smaller erases and discards, we
> may want the benefit the ->card_busy() callback provides us.
> 
> I would suggest that we first try to fix the implementation of the
> ->card_busy() callback for your HW. If that isn't possible or fails,
> then let's consider the approach you have taken in the $subject patch.

Note, sdhci drivers can override host->ops.  For example,
sdhci-omap.c has:

	host->mmc_host_ops.card_busy = sdhci_omap_card_busy;

Probably, if ->card_busy() cannot be supported, then setting
it to NULL would work.

	host->mmc_host_ops.card_busy = NULL; /* Cannot detect card busy */