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

[Marek Vasut]

On Friday, November 06, 2015 at 10:28:31 AM, Gregory CLEMENT wrote:
> Hi Marek,
> 
>  On jeu., nov. 05 2015, Marek Vasut <marex at 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 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?
> 
> 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.

Excellent, thanks for checking this :-)

> > 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>
> 
> Thanks,
> 
> Gregory

Thanks!

Best regards,
Marek Vasut