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

[Gregory CLEMENT <gregory.clement@free-electrons.com>]

Hi Marek,
 
 On jeu., nov. 05 2015, Marek Vasut <marex@denx.de> wrote:

> 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@free-electrons.com>
>> Tested-by: Marek Vasut <marex@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?

curr_clk is set in the mci_set_mode function which is called from
mci_init which is called by the mmc core function mmc_start_init before
any use of a command and especially of mci_send_cmd(). So we are safe.

> 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@denx.de>

Thanks,

Gregory

>
>> +
>>  	return 0;
>>  }
>
> Best regards,
> Marek Vasut

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com