Re: [PATCH 02/11] mmc: dw_mmc: Re-store SDIO IRQs mask at system resume
From: Doug Anderson
Date: Thu Sep 05 2019 - 19:47:25 EST
On Tue, Sep 3, 2019 at 7:22 AM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> In cases when SDIO IRQs have been enabled, runtime suspend is prevented by
> the driver. However, this still means dw_mci_runtime_suspend|resume() gets
> called during system suspend/resume, via pm_runtime_force_suspend|resume().
> This means during system suspend/resume, the register context of the dw_mmc
> device most likely loses its register context, even in cases when SDIO IRQs
> have been enabled.
Even if they weren't lost the resume code currently has this statement:
mci_writel(host, INTMASK, SDMMC_INT_CMD_DONE | SDMMC_INT_DATA_OVER |
SDMMC_INT_TXDR | SDMMC_INT_RXDR |
...so that would have clobbered any existing state even if register
state wasn't lost. ;-)
> To re-enable the SDIO IRQs during system resume, the dw_mmc driver
> currently relies on the mmc core to re-enable the SDIO IRQs when it resumes
> the SDIO card, but this isn't the recommended solution. Instead, it's
> better to deal with this locally in the dw_mmc driver, so let's do that.
> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> drivers/mmc/host/dw_mmc.c | 4 ++++
> 1 file changed, 4 insertions(+)
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index eea52e2c5a0c..f114710e82b4 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -3460,6 +3460,10 @@ int dw_mci_runtime_resume(struct device *dev)
> /* Force setup bus to guarantee available clock output */
> dw_mci_setup_bus(host->slot, true);
> + /* Re-enable SDIO interrupts. */
> + if (sdio_irq_enabled(host->slot->mmc))
> + __dw_mci_enable_sdio_irq(host->slot, 1);
There's a slight bit of subtleness here and I guess we need to figure
out if it matters. From testing things seem to work OK so maybe we're
fine, but just to explain what's bugging me:
If we got an SDIO interrupt that was never ACKed then this is going to
act like an implicit ACK. Notice that dw_mci_ack_sdio_irq() is
exactly this call because when the SDIO IRQ fires we mask it out.
...then unmask when Acked.
Specifically after your series is applied, I think this is what
happens if an interrupt fires while the SDIO bus is officially
1. dw_mci_interrupt() will get called which will mask the SDIO IRQ and
then call sdio_signal_irq()
2. sdio_signal_irq() will queue some delayed work.
3. The work will call sdio_run_irqs()
4. sdio_run_irqs() _won't_ ack the IRQ, so it will stay disabled.
5. When we get to the resume we'll re-enable the interrupt.
I guess that's fine, but it is a little weird that we might not really
be restoring it simply because it got disabled due to the clobbering
of INTMASK but also because we implicitly skipped Acking an interrupt
I wonder if the correct fix is to just add an explit zeroing of the
INTMASK (so mask all interrupts) in dw_mmc's suspend callback. Then
there's no possible way we could get an interrupt during suspend...