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Date:   Wed, 4 Jul 2018 17:29:46 +0200
From:   Maxime Ripard <maxime.ripard@bootlin.com>
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     Marc Zyngier <marc.zyngier@arm.com>,
        Stefan Mavrodiev <stefan@olimex.com>,
        Chen-Yu Tsai <wens@csie.org>,
        "open list:MULTIMEDIA CARD (MMC), SECURE DIGITAL (SD) AND..." 
        <linux-mmc@vger.kernel.org>,
        "moderated list:ARM/Allwinner sunXi SoC support" 
        <linux-arm-kernel@lists.infradead.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/1] mmc: sunxi: Disable irq during pm_suspend
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On Wed, Jul 04, 2018 at 03:34:36PM +0200, Ulf Hansson wrote:
> On 4 July 2018 at 13:34, Marc Zyngier <marc.zyngier@arm.com> wrote:
> > On 04/07/18 11:50, Ulf Hansson wrote:
> >> + Marc
> >>
> >> On 4 July 2018 at 08:28, Stefan Mavrodiev <stefan@olimex.com> wrote:
> >>> When mmc host controller enters suspend state, the clocks are
> >>> disabled, but irqs are not. For some reason the irqchip emits
> >>> false interrupts, which causes system lock loop.
> >>>
> >>> Debug log is:
> >>>   ...
> >>>   sunxi-mmc 1c11000.mmc: setting clk to 52000000, rounded 51200000
> >>>   sunxi-mmc 1c11000.mmc: enabling the clock
> >>>   sunxi-mmc 1c11000.mmc: cmd 13(8000014d) arg 10000 ie 0x0000bbc6 len=
 0
> >>>   sunxi-mmc 1c11000.mmc: irq: rq (ptrval) mi 00000004 idi 00000000
> >>>   sunxi-mmc 1c11000.mmc: cmd 6(80000146) arg 3210101 ie 0x0000bbc6 le=
n 0
> >>>   sunxi-mmc 1c11000.mmc: irq: rq (ptrval) mi 00000004 idi 00000000
> >>>   sunxi-mmc 1c11000.mmc: cmd 13(8000014d) arg 10000 ie 0x0000bbc6 len=
 0
> >>>   sunxi-mmc 1c11000.mmc: irq: rq (ptrval) mi 00000004 idi 00000000
> >>>   mmc1: new DDR MMC card at address 0001
> >>>   mmcblk1: mmc1:0001 AGND3R 14.6 GiB
> >>>   mmcblk1boot0: mmc1:0001 AGND3R partition 1 4.00 MiB
> >>>   mmcblk1boot1: mmc1:0001 AGND3R partition 2 4.00 MiB
> >>>   sunxi-mmc 1c11000.mmc: cmd 18(80003352) arg 0 ie 0x0000fbc2 len 409
> >>>   sunxi-mmc 1c11000.mmc: irq: rq (ptrval) mi 00004000 idi 00000002
> >>>    mmcblk1: p1
> >>>   sunxi-mmc 1c11000.mmc: irq: rq   (null) mi 00000000 idi 00000000
> >>>   sunxi-mmc 1c11000.mmc: irq: rq   (null) mi 00000000 idi 00000000
> >>>   sunxi-mmc 1c11000.mmc: irq: rq   (null) mi 00000000 idi 00000000
> >>>   sunxi-mmc 1c11000.mmc: irq: rq   (null) mi 00000000 idi 00000000
> >>> and so on...
> >>>
> >>> This issue apears on eMMC cards, routed on MMC2 slot. The patch is
> >>> tested with A20-OLinuXino-MICRO/LIME/LIME2 boards.
> >>>
> >>> Fixes: 9a8e1e8cc2c0 ("mmc: sunxi: Add runtime_pm support")
> >>> Signed-off-by: Stefan Mavrodiev <stefan@olimex.com>
> >>> ---
> >>>  Changes in v2:
> >>>   - Add comment why disable_irq() is necessary
> >>>
> >>> ---
> >>>  drivers/mmc/host/sunxi-mmc.c | 7 +++++++
> >>>  1 file changed, 7 insertions(+)
> >>>
> >>> diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mm=
c.c
> >>> index e747259..8e7f3e3 100644
> >>> --- a/drivers/mmc/host/sunxi-mmc.c
> >>> +++ b/drivers/mmc/host/sunxi-mmc.c
> >>> @@ -1446,6 +1446,7 @@ static int sunxi_mmc_runtime_resume(struct devi=
ce *dev)
> >>>         sunxi_mmc_init_host(host);
> >>>         sunxi_mmc_set_bus_width(host, mmc->ios.bus_width);
> >>>         sunxi_mmc_set_clk(host, &mmc->ios);
> >>> +       enable_irq(host->irq);
> >>>
> >>>         return 0;
> >>>  }
> >>> @@ -1455,6 +1456,12 @@ static int sunxi_mmc_runtime_suspend(struct de=
vice *dev)
> >>>         struct mmc_host *mmc =3D dev_get_drvdata(dev);
> >>>         struct sunxi_mmc_host *host =3D mmc_priv(mmc);
> >>>
> >>> +       /*
> >>> +        * When clocks are off, it's possible receiving
> >>> +        * fake interrupts, which will stall the system.
> >>> +        * Disabling the irq  will prevent this.
> >>> +        */
> >>> +       disable_irq(host->irq);
> >>
> >> No, this doesn't work for shared IRQs.
> >
> > Well, in this case, it does work, because that interrupt line cannot be
> > shared with anything else, if I understand how the SoC is wired: each
> > MMC controller has a dedicated interrupt line to the GIC, and it isn't
> > shared with anything (that's on the A20 though, and I don't know about
> > other SoCs integrating the same IP).
>=20
> That's the problem. This may work on some SoCs but not on others.

I don't really expect that driver to be used on some other SoCs, and
if that ever happens, maybe we can fix it when it does?

Maxime

--=20
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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