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SubjectRe: [PATCH 1/2] mmc: add unstuck function if host is in deadlock state
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Le 10/21/19 à 3:35 PM, Ulf Hansson a écrit :
> On Fri, 11 Oct 2019 at 15:15, Ludovic Barre <ludovic.Barre@st.com> wrote:
>>
>> From: Ludovic Barre <ludovic.barre@st.com>
>>
>> After a request a host may be in deadlock state, and wait
>> a specific action to unstuck the hardware block before
>> re-sending a new command.
>
> Rather than talking about "unstuck" and "deadlock", how about instead
> describing that an MMC controller, may end up in an non-functional
> state hanging on something. Then to allow it to serve new requests it
> needs to be reset.
>

Ok, deadlock naming is perhaps too stronght and scary.

>>
>> This patch adds an optional callback mmc_hw_unstuck which
>> allows the host to unstuck the controller. In order to avoid
>> a critical context, this callback must be called when the
>> request is completed. Depending the mmc request, the completion
>> function is defined by mrq->done and could be in block.c or core.c.
>
> I think it's important to state exactly what is expected from the core
> perspective, by the mmc host driver when it calls this new host ops.
> We need to clarify that.
>
>>
>> mmc_hw_unstuck is called if the host returns an cmd/sbc/stop/data
>> DEADLK error.
>
> To me, this approach seems a bit upside-down. Although, I have to
> admit that I haven't thought through this completely yet.
>
> The thing is, to make this useful for host drivers in general, I
> instead think we need to add timeout to each request that the core
> sends to the host driver. In other words, rather than waiting forever
> in the core for the completion variable to be set, via calling
> wait_for_completion() we could call wait_for_completion_timeout(). The
> tricky part is to figure out what timeout to use for each request.
> Perhaps that is even why you picked the approach as implemented in
> @subject patch instead?

On STM32 SDMMC variant, If datatimeout occurs on R1B request the Data
Path State Machine stays in busy and only the DPSM is non-functional.
The hardware block waits a software action to abort the DPSM.

Like the CPSM stay alive, the framework can sent some requests
(without data, example cmd13:status) before to had this
timeout issue.

POV framework I understand the possibility to have a completion_timeout,
for more safety. But for this specific sdmmc case, I'm not fan, because
the completion timeout error will occur several requests after the real
issue (which put the DPSM non-functional). when the completion timeout
occurs we can't know if it's due to R1B timeout or an other issue.

To resolve the SDMMC's specificity, I can proposed you to add a threaded
irq in mmci drivers to abort the DPSM and terminate the request.

>
> Anyway, the typical scenario I see, is that the host driver is
> hanging, likely waiting for an IRQ that never get raised. So, unless
> it implements it own variant of a "request timeout" mechanism, it
> simple isn't able to call mmc_request_done() to inform the core about
> that the request has failed.
>
> For comments to the code, I defer that to the next step, when we have
> agreed on the way forward.
>
> Kind regards
> Uffe
>
>>
>> Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
>> ---
>> drivers/mmc/core/block.c | 11 +++++++++++
>> drivers/mmc/core/core.c | 35 +++++++++++++++++++++++++++++++++--
>> include/linux/mmc/core.h | 1 +
>> include/linux/mmc/host.h | 7 +++++++
>> 4 files changed, 52 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
>> index 2c71a434c915..2f723e2f5fde 100644
>> --- a/drivers/mmc/core/block.c
>> +++ b/drivers/mmc/core/block.c
>> @@ -1799,6 +1799,17 @@ static void mmc_blk_mq_rw_recovery(struct mmc_queue *mq, struct request *req)
>> u32 blocks;
>> int err;
>>
>> + /*
>> + * if the host return a deadlock, it needs to be unstuck
>> + * before to send a new command.
>> + */
>> + if (brq->sbc.error == -EDEADLK || brq->cmd.error == -EDEADLK ||
>> + brq->stop.error == -EDEADLK || brq->data.error == -EDEADLK) {
>> + pr_err("%s: host is in bad state, must be unstuck\n",
>> + req->rq_disk->disk_name);
>> + mmc_hw_unstuck(card->host);
>> + }
>> +
>> /*
>> * Some errors the host driver might not have seen. Set the number of
>> * bytes transferred to zero in that case.
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 221127324709..43fe59a7403b 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -397,6 +397,7 @@ static int __mmc_start_req(struct mmc_host *host, struct mmc_request *mrq)
>> void mmc_wait_for_req_done(struct mmc_host *host, struct mmc_request *mrq)
>> {
>> struct mmc_command *cmd;
>> + int sbc_err, stop_err, data_err;
>>
>> while (1) {
>> wait_for_completion(&mrq->completion);
>> @@ -420,8 +421,24 @@ void mmc_wait_for_req_done(struct mmc_host *host, struct mmc_request *mrq)
>> mmc_hostname(host), __func__);
>> }
>> }
>> - if (!cmd->error || !cmd->retries ||
>> - mmc_card_removed(host->card))
>> +
>> + sbc_err = mrq->sbc ? mrq->sbc->error : 0;
>> + stop_err = mrq->stop ? mrq->stop->error : 0;
>> + data_err = mrq->data ? mrq->data->error : 0;
>> +
>> + /*
>> + * if the host return a deadlock, it needs to be unstuck
>> + * before to send a new command.
>> + */
>> + if (cmd->error == -EDEADLK || sbc_err == -EDEADLK ||
>> + stop_err == -EDEADLK || data_err == -EDEADLK) {
>> + pr_debug("%s: host is in bad state, must be unstuck\n",
>> + mmc_hostname(host));
>> + mmc_hw_unstuck(host);
>> + }
>> +
>> + if ((!cmd->error && !sbc_err && !stop_err && !data_err) ||
>> + !cmd->retries || mmc_card_removed(host->card))
>> break;
>>
>> mmc_retune_recheck(host);
>> @@ -430,6 +447,12 @@ void mmc_wait_for_req_done(struct mmc_host *host, struct mmc_request *mrq)
>> mmc_hostname(host), cmd->opcode, cmd->error);
>> cmd->retries--;
>> cmd->error = 0;
>> + if (mrq->sbc)
>> + mrq->sbc->error = 0;
>> + if (mrq->stop)
>> + mrq->stop->error = 0;
>> + if (mrq->data)
>> + mrq->data->error = 0;
>> __mmc_start_request(host, mrq);
>> }
>>
>> @@ -2161,6 +2184,14 @@ int mmc_sw_reset(struct mmc_host *host)
>> }
>> EXPORT_SYMBOL(mmc_sw_reset);
>>
>> +void mmc_hw_unstuck(struct mmc_host *host)
>> +{
>> + if (!host->ops->hw_unstuck)
>> + return;
>> + host->ops->hw_unstuck(host);
>> +}
>> +EXPORT_SYMBOL(mmc_hw_unstuck);
>> +
>> static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq)
>> {
>> host->f_init = freq;
>> diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
>> index b7ba8810a3b5..eb10b8194073 100644
>> --- a/include/linux/mmc/core.h
>> +++ b/include/linux/mmc/core.h
>> @@ -173,6 +173,7 @@ void mmc_wait_for_req(struct mmc_host *host, struct mmc_request *mrq);
>> int mmc_wait_for_cmd(struct mmc_host *host, struct mmc_command *cmd,
>> int retries);
>>
>> +void mmc_hw_unstuck(struct mmc_host *host);
>> int mmc_hw_reset(struct mmc_host *host);
>> int mmc_sw_reset(struct mmc_host *host);
>> void mmc_set_data_timeout(struct mmc_data *data, const struct mmc_card *card);
>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
>> index ba703384bea0..8b52cafcd1eb 100644
>> --- a/include/linux/mmc/host.h
>> +++ b/include/linux/mmc/host.h
>> @@ -163,6 +163,13 @@ struct mmc_host_ops {
>> void (*hw_reset)(struct mmc_host *host);
>> void (*card_event)(struct mmc_host *host);
>>
>> + /*
>> + * Optional callback, if your host could be in deadlock after a command
>> + * and need a specific action to unstuck the controller before sending
>> + * new command.
>> + */
>> + void (*hw_unstuck)(struct mmc_host *host);
>> +
>> /*
>> * Optional callback to support controllers with HW issues for multiple
>> * I/O. Returns the number of supported blocks for the request.
>> --
>> 2.17.1
>>

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