linux-kernel - Re: [PATCH 02/11] mmc: dw_mmc: Re-store SDIO IRQs mask at system resume

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Date:   Wed, 4 Sep 2019 17:14:22 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-mmc@...r.kernel.org, Adrian Hunter <adrian.hunter@...el.com>,
        Douglas Anderson <dianders@...omium.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Yong Mao <yong.mao@...iatek.com>,
        Chaotian Jing <chaotian.jing@...iatek.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/11] mmc: dw_mmc: Re-store SDIO IRQs mask at system
 resume

On Tue, Sep 03, 2019 at 04:21:58PM +0200, Ulf Hansson 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.
> 
> 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@...aro.org>
> ---
>  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);
> +
>  	/* Now that slots are all setup, we can enable card detect */
>  	dw_mci_enable_cd(host);

Looks reasonable to me, besides the bikeshedding over
'sdio_irq_enabled' (in "mmc: core: Add helper function to indicate
if SDIO IRQs is enabled").

One thing I wonder is why this change is only needed for dw_mmc and
mtk-sd, but not for others like sunxi_mmc. Any insights for a SDIO
newb?