linux-kernel - Re: [RESEND v3 3/3] mmc: mediatek: add support for SDIO eint IRQ

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Date:   Tue, 18 Jan 2022 11:18:57 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Axe Yang <axe.yang@...iatek.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Chaotian Jing <chaotian.jing@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Satya Tangirala <satyat@...gle.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Lucas Stach <dev@...xeye.de>,
        Eric Biggers <ebiggers@...gle.com>,
        Andrew Jeffery <andrew@...id.au>,
        Stephen Boyd <swboyd@...omium.org>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        Yue Hu <huyue2@...ong.com>, Tian Tao <tiantao6@...ilicon.com>,
        angelogioacchino.delregno@...labora.com, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Yong Mao <yong.mao@...iatek.com>
Subject: Re: [RESEND v3 3/3] mmc: mediatek: add support for SDIO eint IRQ

On Mon, Jan 17, 2022 at 7:33 PM Axe Yang <axe.yang@...iatek.com> wrote:
>
> Add support for eint IRQ when MSDC is used as an SDIO host. This
> feature requires SDIO device support async IRQ function. With this
> feature, SDIO host can be awakened by SDIO card in suspend state,
> without additional pin.
>
> MSDC driver will time-share the SDIO DAT1 pin. During suspend, MSDC
> turn off clock and switch SDIO DAT1 pin to GPIO mode. And during
> resume, switch GPIO function back to DAT1 mode then turn on clock.
>
> Some device tree property should be added or modified in MSDC node
> to support SDIO eint IRQ. Pinctrls named state_dat1 and state_eint
> are mandatory. And cap-sdio-async-irq flag is necessary since this
> feature depends on asynchronous interrupt:
>         &mmcX {
>                 ...
>                 pinctrl-names = "default", "state_uhs", "state_eint",
>                                 "state_dat1";
>                 ...
>                 pinctrl-2 = <&mmc2_pins_eint>;
>                 pinctrl-3 = <&mmc2_pins_dat1>;
>                 ...
>                 cap-sdio-async-irq;
>                 ...
>         };

...

> +static irqreturn_t msdc_sdio_eint_irq(int irq, void *dev_id)
> +{
> +       struct msdc_host *host = dev_id;
> +       struct mmc_host *mmc = mmc_from_priv(host);

> +       unsigned long flags;

Same Q as per v2. Why do you need this?

Yes, you did the first step to the answer, but I want you to go deeper
and tell me why you need the spin_lock_irqsave() variant.

> +       spin_lock_irqsave(&host->lock, flags);
> +       if (likely(host->sdio_irq_cnt > 0)) {
> +               disable_irq_nosync(host->eint_irq);
> +               disable_irq_wake(host->eint_irq);
> +               host->sdio_irq_cnt--;
> +       }
> +       spin_unlock_irqrestore(&host->lock, flags);
> +
> +       sdio_signal_irq(mmc);
> +
> +       return IRQ_HANDLED;
> +}

-- 
With Best Regards,
Andy Shevchenko