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Date: Fri, 15 Nov 2019 15:59:47 +0100
From: Ludovic BARRE <ludovic.barre@...com>
To: Ulf Hansson <ulf.hansson@...aro.org>
CC: Rob Herring <robh+dt@...nel.org>,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Alexandre Torgue <alexandre.torgue@...com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
DTML <devicetree@...r.kernel.org>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
<linux-stm32@...md-mailman.stormreply.com>
Subject: Re: [PATCH 1/1] mmc: mmci: add threaded irq to abort DPSM of
non-functional state
hi Ulf
Le 11/14/19 à 4:09 PM, Ulf Hansson a écrit :
> On Wed, 13 Nov 2019 at 18:25, Ludovic Barre <ludovic.Barre@...com> wrote:
>>
>> From: Ludovic Barre <ludovic.barre@...com>
>>
>> If datatimeout occurs on R1B request, the Data Path State Machine stays
>> in busy and is non-functional. Only a reset aborts the DPSM.
>
> Please clarify/extend this information to tell that this is for the
> variant, that keeps DPSM enabled and uses the data timer while sending
> a CMD12. Or something along those lines.
>
yes, of course.
>>
>> Like a reset must be outside of critical section, this patch adds
>
> /s/critical section/atomic context
OK, thanks
>
>> threaded irq function to release state machine. In this case,
>> the mmc_request_done is called at the end of threaded irq and
>> skipped into irq handler.
>>
>> Signed-off-by: Ludovic Barre <ludovic.barre@...com>
>> ---
>> drivers/mmc/host/mmci.c | 44 ++++++++++++++++++++++++++++++++++++-----
>> drivers/mmc/host/mmci.h | 1 +
>> 2 files changed, 40 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
>> index 40e72c30ea84..ec6e249c87ca 100644
>> --- a/drivers/mmc/host/mmci.c
>> +++ b/drivers/mmc/host/mmci.c
>> @@ -556,6 +556,9 @@ static void mmci_dma_error(struct mmci_host *host)
>> static void
>> mmci_request_end(struct mmci_host *host, struct mmc_request *mrq)
>> {
>> + if (host->irq_action == IRQ_WAKE_THREAD)
>> + return;
>> +
>> writel(0, host->base + MMCICOMMAND);
>>
>> BUG_ON(host->data);
>> @@ -1321,6 +1324,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
>> } else if (host->variant->busy_timeout && busy_resp &&
>> status & MCI_DATATIMEOUT) {
>> cmd->error = -ETIMEDOUT;
>> + host->irq_action = IRQ_WAKE_THREAD;
>> } else {
>> cmd->resp[0] = readl(base + MMCIRESPONSE0);
>> cmd->resp[1] = readl(base + MMCIRESPONSE1);
>> @@ -1532,9 +1536,9 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
>> {
>> struct mmci_host *host = dev_id;
>> u32 status;
>> - int ret = 0;
>>
>> spin_lock(&host->lock);
>> + host->irq_action = IRQ_HANDLED;
>>
>> do {
>> status = readl(host->base + MMCISTATUS);
>> @@ -1574,12 +1578,41 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
>> if (host->variant->busy_detect_flag)
>> status &= ~host->variant->busy_detect_flag;
>>
>> - ret = 1;
>> } while (status);
>>
>> spin_unlock(&host->lock);
>>
>> - return IRQ_RETVAL(ret);
>> + return host->irq_action;
>> +}
>> +
>> +/*
>> + * mmci_irq_threaded is call if the mmci host need to release state machines
>> + * before to terminate the request.
>> + * If datatimeout occurs on R1B request, the Data Path State Machine stays
>> + * in busy and is non-functional. Only a reset can to abort the DPSM.
>> + */
>> +static irqreturn_t mmci_irq_threaded(int irq, void *dev_id)
>> +{
>> + struct mmci_host *host = dev_id;
>> + unsigned long flags;
>> +
>> + if (host->rst) {
>> + reset_control_assert(host->rst);
>> + udelay(2);
>> + reset_control_deassert(host->rst);
>> + }
>> +
>> + spin_lock_irqsave(&host->lock, flags);
>> + writel(host->clk_reg, host->base + MMCICLOCK);
>> + writel(host->pwr_reg, host->base + MMCIPOWER);
>> + writel(MCI_IRQENABLE | host->variant->start_err,
>> + host->base + MMCIMASK0);
>> +
>> + host->irq_action = IRQ_HANDLED;
>> + mmci_request_end(host, host->mrq);
>> + spin_unlock_irqrestore(&host->lock, flags);
>> +
>> + return host->irq_action;
>> }
>>
>> static void mmci_request(struct mmc_host *mmc, struct mmc_request *mrq)
>> @@ -2071,8 +2104,9 @@ static int mmci_probe(struct amba_device *dev,
>> goto clk_disable;
>> }
>>
>> - ret = devm_request_irq(&dev->dev, dev->irq[0], mmci_irq, IRQF_SHARED,
>> - DRIVER_NAME " (cmd)", host);
>> + ret = devm_request_threaded_irq(&dev->dev, dev->irq[0], mmci_irq,
>> + mmci_irq_threaded, IRQF_SHARED,
>> + DRIVER_NAME " (cmd)", host);
>
> In general it's a good idea to move drivers into using a threaded IRQ handler.
>
> However, the reason this hasn't been done for mmci before, is because
> there are some legacy variants, that doesn't support HW flow control.
With this patch, the mmci_irq_threaded is called only when
a datatimeout occurs on R1B request else the mmci_irq return IRQ_HANDLED
and the threaded irq is not called.
So normally, there is no impact for legacy variants.
>
> Unless I am mistaken, that means when the fifo gets full during data
> transfers - it's too late to act. In other words, running the handler
> in hard IRQ context, should increase the probability of not missing
> the deadline.
>
> If a threaded IRQ handler also is sufficient for these legacy
> variants, only tests can tell.
>
> An option, would be to use a threaded handler for those variants that
> supports HW flow control. Not sure how messy the code would be with
> this option, perhaps you can give this a try?
For all these reasons you mentioned above, I'm not sure it's safe to
extend the thread manager to anything other than "aborting the DPSM" on
R1B datatiemout ? what do you think about that?
I prefer just used the irq threaded for specific errors case which need
be outside of atomic context.
>
>
>> if (ret)
>> goto clk_disable;
>>
>> diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
>> index 158e1231aa23..5e63c0596364 100644
>> --- a/drivers/mmc/host/mmci.h
>> +++ b/drivers/mmc/host/mmci.h
>> @@ -412,6 +412,7 @@ struct mmci_host {
>>
>> struct timer_list timer;
>> unsigned int oldstat;
>> + u32 irq_action;
>>
>> /* pio stuff */
>> struct sg_mapping_iter sg_miter;
>> --
>> 2.17.1
>>
>
> Kind regards
> Uffe
>
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