On Tue, Sep 03, 2019 at 04:22:04PM +0200, Ulf Hansson wrote:
> System suspend/resume of SDIO cards, with SDIO IRQs enabled and when using
> MMC_CAP2_SDIO_IRQ_NOTHREAD is unfortunate still suffering from a fragile
> behaviour. Some problems have been taken care of so far, but more issues
> remains.
>
> For example, calling the ->ack_sdio_irq() callback to let host drivers
> re-enable the SDIO IRQs is a bad idea, unless the IRQ have been consumed,
> which may not be the case during system suspend/resume. This may lead to
> that a host driver re-signals the same SDIO IRQ over and over again,
> causing a storm of IRQs and gives a ping-pong effect towards the
> sdio_irq_work().
>
> Moreover, calling the ->enable_sdio_irq() callback at system resume to
> re-enable already enabled SDIO IRQs for the host, causes the runtime PM
> count for some host drivers to become in-balanced. This then leads to the
> host to remain runtime resumed, no matter if it's needed or not.
>
> To fix these problems, let's check if process_sdio_pending_irqs() actually
> consumed the SDIO IRQ, before we continue to ack the IRQ by invoking the
> ->ack_sdio_irq() callback.
>
> Additionally, there should be no need to re-enable SDIO IRQs as the host
> driver already knows if they were enabled at system suspend, thus also
> whether it needs to re-enable them at system resume. For this reason, drop
> the call to ->enable_sdio_irq() during system resume.
>
> In regards to these changes there is yet another issue, which is when there
> is an SDIO IRQ being signaled by the host driver, but after the SDIO card
> has been system suspended. Currently these IRQs are just thrown away, while
> we should at least make sure to try to consume them when the SDIO card has
> been system resumed. Fix this by calling sdio_signal_irq() after system
> resumed the SDIO card.
>
> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> ---
> drivers/mmc/core/sdio.c | 2 +-
> drivers/mmc/core/sdio_irq.c | 3 ++-
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> index c557f1519b77..3114d496495a 100644
> --- a/drivers/mmc/core/sdio.c
> +++ b/drivers/mmc/core/sdio.c
> @@ -1015,7 +1015,7 @@ static int mmc_sdio_resume(struct mmc_host *host)
> if (!(host->caps2 & MMC_CAP2_SDIO_IRQ_NOTHREAD))
> wake_up_process(host->sdio_irq_thread);
> else if (host->caps & MMC_CAP_SDIO_IRQ)
> - host->ops->enable_sdio_irq(host, 1);
> + sdio_signal_irq(host);
You could possibly limit this to cards that remain powered during
suspend, but doing it always should do no harm.
> }
>
> out:
> diff --git a/drivers/mmc/core/sdio_irq.c b/drivers/mmc/core/sdio_irq.c
> index d7965b53a6d2..900871073bd7 100644
> --- a/drivers/mmc/core/sdio_irq.c
> +++ b/drivers/mmc/core/sdio_irq.c
> @@ -115,7 +115,8 @@ static void sdio_run_irqs(struct mmc_host *host)
> mmc_claim_host(host);
> if (host->sdio_irqs) {
> process_sdio_pending_irqs(host);
> - host->ops->ack_sdio_irq(host);
> + if (!host->sdio_irq_pending)
> + host->ops->ack_sdio_irq(host);
> }
> mmc_release_host(host);
> }
I'm by no means a SDIO expert, but as far as I can tell this looks
good. I verified that this patch fixes a problem with SDIO interrupts
that are ignored while suspending.
Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
