[U-Boot] [PATCH v2] mmc: atmel: Properly fix clock configuration

[Marek Vasut]

On Thursday, November 05, 2015 at 08:58:30 PM, Gregory CLEMENT wrote:
> Timing issue occurs on eMMC not only when modifying the frequency but
> also for all the switch command(CMD6). According to the MMC spec waiting
> 8 clocks after a switch command would be the thing to do.
> 
> This patch allows fixing CPU hang observed when trying to changing the
> bus width on a eMMC on SAMA5D4.
> 
> Signed-off-by: Gregory CLEMENT <gregory.clement at free-electrons.com>
> Tested-by: Marek Vasut <marex at denx.de> # on DENX MA5D4EV
> ---
>  drivers/mmc/gen_atmel_mci.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/gen_atmel_mci.c b/drivers/mmc/gen_atmel_mci.c
> index da870c6..f090b27 100644
> --- a/drivers/mmc/gen_atmel_mci.c
> +++ b/drivers/mmc/gen_atmel_mci.c
> @@ -36,6 +36,7 @@ struct atmel_mci_priv {
>  	struct mmc_config	cfg;
>  	struct atmel_mci	*mci;
>  	unsigned int		initialized:1;
> +	unsigned int		curr_clk;
>  };
> 
>  /* Read Atmel MCI IP version */
> @@ -91,7 +92,10 @@ static void mci_set_mode(struct mmc *mmc, u32 hz, u32
> blklen)
> 
>  		}
>  	}
> -
> +	if (version >= 0x500)
> +		priv->curr_clk = bus_hz / (clkdiv * 2 + clkodd + 2);
> +	else
> +		priv->curr_clk = (bus_hz / (clkdiv + 1)) / 2;
>  	blklen &= 0xfffc;
> 
>  	mr = MMCI_BF(CLKDIV, clkdiv);
> @@ -118,8 +122,6 @@ static void mci_set_mode(struct mmc *mmc, u32 hz, u32
> blklen) if (mmc->card_caps & mmc->cfg->host_caps & MMC_MODE_HS)
>  		writel(MMCI_BIT(HSMODE), &mci->cfg);
> 
> -	udelay(50);
> -
>  	priv->initialized = 1;
>  }
> 
> @@ -323,6 +325,13 @@ mci_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd,
> struct mmc_data *data) }
>  	}
> 
> +	/*
> +	 * After the switch command, wait for 8 clocks before the next
> +	 * command
> +	 */
> +	if (cmd->cmdidx == MMC_CMD_SWITCH)
> +		udelay(8*1000000/ priv->curr_clk); /* 8 clk in us */

Is there a chance that curr_clk will be inited to zero and this would be called?
I guess the easy fix is to init curr_clk to 1 in the probe() call. Sorry that I
didn't mention this earlier.

Otherwise,

Acked-by: Marek Vasut <marex at denx.de>

> +
>  	return 0;
>  }

Best regards,
Marek Vasut