[U-Boot] [PATCH v2] mmc: fsl_esdhc: Avoid infinite loop in esdhc_send_cmd_common()

[Ricardo Salveti]

Hi Fabio,

On Mon, Nov 19, 2018 at 10:31 AM Fabio Estevam <festevam at gmail.com> wrote:
>
> The following hang is observed on a Hummingboard 2 MicroSOM
> i2eX iMX6D - rev 1.3 with no eMMC populated on board:
>
> U-Boot SPL 2018.11+gf6206f8587 (Nov 16 2018 - 00:56:34 +0000)
> Trying to boot from MMC1
>
> U-Boot 2018.11+gf6206f8587 (Nov 16 2018 - 00:56:34 +0000)
>
> CPU:   Freescale i.MX6D rev1.5 996 MHz (running at 792 MHz)
> CPU:   Extended Commercial temperature grade (-20C to 105C) at 33C
> Reset cause: POR
> Board: MX6 HummingBoard2
> DRAM:  1 GiB
> MMC:   FSL_SDHC: 0, FSL_SDHC: 1
> Loading Environment from MMC... *** Warning - bad CRC, using default environment
>
> No panel detected: default to HDMI
> Display: HDMI (1024x768)
> In:    serial
> Out:   serial
> Err:   serial
> ---> hangs
>
> which is caused by the following infinite loop inside esdhc_send_cmd_common()
>
>         while (!(esdhc_read32(&regs->irqstat) & flags))
>                 ;
>
> Instead of looping forever, provide an exit path so that a timeout
> error can be propagated in the case irqstat does not report
> any interrupts, which may happen when no eMMC is populated on
> board.
>
> Reported-by: Ricardo Salveti <rsalveti at rsalveti.net>
> Signed-off-by: Fabio Estevam <festevam at gmail.com>
> ---
> Changes since v1:
> - Jump to the label out on error path (Baruch).
>
>  drivers/mmc/fsl_esdhc.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/fsl_esdhc.c b/drivers/mmc/fsl_esdhc.c
> index 3cdfa7f..b8d0b00 100644
> --- a/drivers/mmc/fsl_esdhc.c
> +++ b/drivers/mmc/fsl_esdhc.c
> @@ -396,6 +396,7 @@ static int esdhc_send_cmd_common(struct fsl_esdhc_priv *priv, struct mmc *mmc,
>         uint    irqstat;
>         u32     flags = IRQSTAT_CC | IRQSTAT_CTOE;
>         struct fsl_esdhc *regs = priv->esdhc_regs;
> +       unsigned long start;
>
>  #ifdef CONFIG_SYS_FSL_ERRATUM_ESDHC111
>         if (cmd->cmdidx == MMC_CMD_STOP_TRANSMISSION)
> @@ -453,8 +454,13 @@ static int esdhc_send_cmd_common(struct fsl_esdhc_priv *priv, struct mmc *mmc,
>                 flags = IRQSTAT_BRR;
>
>         /* Wait for the command to complete */
> -       while (!(esdhc_read32(&regs->irqstat) & flags))
> -               ;
> +       start = get_timer(0);
> +       while (!(esdhc_read32(&regs->irqstat) & flags)) {
> +               if (get_timer(start) > 1000) {
> +                       err = -ETIMEDOUT;
> +                       goto out;
> +               }
> +       }

This fixes the hang I was having, but adds a significant boot delay
because it needs to wait until it gets the timeout (1000). Is there a
better timeout value to be used here?

Thanks,
-- 
Ricardo Salveti de Araujo