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Date: Thu, 14 Nov 2019 16:09:22 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Ludovic Barre <ludovic.Barre@...com>
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
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.
>
> Like a reset must be outside of critical section, this patch adds
/s/critical section/atomic context
> 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.
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?
> 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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