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

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Date:   Wed, 19 Jan 2022 18:11:43 +0800
From:   Axe Yang <axe.yang@...iatek.com>
To:     Andy Shevchenko <andy.shevchenko@...il.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 Tue, 2022-01-18 at 11:18 +0200, Andy Shevchenko wrote:
> 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.

You are right, no need to save/restore flags in irq handler.
Will fix it in new version.
Thanks.

> 
> > +       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;
> > +}
> 
>