Re: Self-detected stall on CPU when using SD card

[Stefan Agner <stefan@agner.ch>]

On 26.06.2018 12:53, Stefan Agner wrote:
> Hi,
> 
> On our Colibri iMX6 (arch/arm/boot/dts/imx6qdl-colibri.dtsi) we
> experience the following stack trace when a SD card is plugged in:
> 

[...]

> [<c08396f4>] (esdhc_pltfm_set_clock) from [<c083622c>]
> (sdhci_set_ios+0xd8/0x584)
>  r10:ffffe000 r9:c1105900 r8:00004097 r7:d818f2e8 r6:d818f480
> r5:d818f2e8
>  r4:d818f000
> [<c0836154>] (sdhci_set_ios) from [<c0836070>]
> (sdhci_runtime_resume_host+0xa0/0x184)
>  r9:c1105900 r8:00004097 r7:d818f2e8 r6:d818f648 r5:d818f000 r4:d818f480

[...]

> 
> It used to work in v4.9, so I started a git bisect. It pointed me to
> this commit:
> 
> Commit d1e4f74f911d ("mmc: sdhci: Do not use spin lock in set_ios
> paths").
> 
> Reverting the commit on-top of v4.18-rc1 seems to fix the issue too.
> 
> Any idea?

I figured out that the same platform had a GPIO Key which triggered all
the time. This seems to exacerbate the MMC issue such that it triggers
on very boot, about rootfs mount time.

This change seems to fix the issue as well, not sure though whether this
is a proper fix:

--- a/drivers/mmc/host/sdhci-esdhc-imx.c
+++ b/drivers/mmc/host/sdhci-esdhc-imx.c
@@ -697,6 +697,7 @@ static inline void esdhc_pltfm_set_clock(struct
sdhci_host *host,
        int ddr_pre_div = imx_data->is_ddr ? 2 : 1;
        int pre_div = 1;
        int div = 1;
+       unsigned long flags;
        u32 temp, val;
 
        if (clock == 0) {
@@ -724,6 +725,7 @@ static inline void esdhc_pltfm_set_clock(struct
sdhci_host *host,
                        pre_div = 2;
        }
 
+       spin_lock_irqsave(&host->lock, flags);
        temp = sdhci_readl(host, ESDHC_SYSTEM_CONTROL);
        temp &= ~(ESDHC_CLOCK_IPGEN | ESDHC_CLOCK_HCKEN |
ESDHC_CLOCK_PEREN
                | ESDHC_CLOCK_MASK);
@@ -754,6 +756,7 @@ static inline void esdhc_pltfm_set_clock(struct
sdhci_host *host,
                writel(val | ESDHC_VENDOR_SPEC_FRC_SDCLK_ON,
                host->ioaddr + ESDHC_VENDOR_SPEC);
        }
+       spin_unlock_irqrestore(&host->lock, flags);
 
        mdelay(1);
 }

--
Stefan