[U-Boot] [PATCH] Revert "mmc: fsl_esdhc: fix sd/mmc ddr mode clock setting issue"

Peng Fan peng.fan at nxp.com
Thu May 9 01:16:15 UTC 2019 

> Subject: Re: [PATCH] Revert "mmc: fsl_esdhc: fix sd/mmc ddr mode clock
> setting issue"
> 
> On Wed, 8 May 2019 13:59:14 +0000
> Peng Fan <peng.fan at nxp.com> wrote:
> 
> > > -----Original Message-----
> > > From: Lukasz Majewski [mailto:lukma at denx.de]
> > > Sent: 2019年5月8日 14:38
> > > To: Peng Fan <peng.fan at nxp.com>
> > > Cc: u-boot at lists.denx.de; Tom Rini <trini at konsulko.com>; Marcel
> > > Ziswiler <marcel.ziswiler at toradex.com>; Fabio Estevam
> > > <fabio.estevam at nxp.com>; dl-uboot-imx <uboot-imx at nxp.com>;
> > > sbabic at denx.de; Stefan Agner <stefan.agner at toradex.com>; BOUGH
> CHEN
> > > <haibo.chen at nxp.com>; Ye Li <ye.li at nxp.com>
> > > Subject: Re: [PATCH] Revert "mmc: fsl_esdhc: fix sd/mmc ddr mode
> > > clock setting issue"
> > >
> > > On Wed, 8 May 2019 08:19:45 +0200
> > > Lukasz Majewski <lukma at denx.de> wrote:
> > >
> > > > Hi Peng,
> > > >
> > > > > Hi Lukasz,
> > > > >
> > > > > > Subject: [PATCH] Revert "mmc: fsl_esdhc: fix sd/mmc ddr mode
> > > > > > clock setting issue"
> > > > > >
> > > > > > This reverts commit
> 72a89e0da5ac6a4ab929b15a2b656f04f50767f6,
> > > > > > which causes the imx53 HSC to hang as the eMMC is not working
> > > > > > properly anymore.
> > > > > >
> > > > > > The exact error message:
> > > > > > MMC write: dev # 0, block # 2, count 927 ... mmc write failed
> > > > > > 0 blocks written: ERROR
> > > > > >
> > > > > > imx53 is not using the DDR mode.
> > > > > >
> > > > > > Debugging of pre_div and div generation showed that those
> > > > > > values are generated in a way, which is not matching the ones
> > > > > > from working setup.
> > > > > >
> > > > > > As the original patch was performing code refactoring, let's
> > > > > > revert this change, so all imx53 boards would work again.
> > > > >
> > > > > Could you share what is the clock value for your board?
> > > >
> > > > Sure, no problem:
> > > >
> > > > Working setup:
> > > > --------------
> > > >
> > > > MMC:
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 8 div: 12 set_sysctl: clk: 2240
> > > > FSL_SDHC: 0
> > > > Loading Environment from MMC...
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 8 div: 12 set_sysctl: clk: 2240
> > > >
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 8 div: 12 set_sysctl: clk: 2240
> > > >
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 1 div: 1 set_sysctl: clk: 272
> > > >
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 1 div: 0 set_sysctl: clk: 256
> > > >
> > > >
> > > >
> > > >
> > > > Broken:
> > > > -------
> > > > MMC:
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 8 div: 12 set_sysctl: clk: 2240
> > > > FSL_SDHC: 0
> > > > Loading Environment from MMC...
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 8 div: 12 set_sysctl: clk: 2240
> > > >
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 8 div: 12 set_sysctl: clk: 2240
> > > >
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 0 div: 3 set_sysctl: clk: 48
> > > >
> > > > set_sysctl: pre_div = 2 mmc->ddr: 0 sdhc_clk: 80000000
> > > >  pre_div: 0 div: 1 set_sysctl: clk: 16
> > > >
> > > >
> > > > (Please also find attached patch to reproduce debug output).
> > > >
> > >
> > > And maybe the most important question - why it was necessary to
> > > refactor this code?
> > >
> > > Parts responsible for calculating pre_div and div seems not related
> > > to ddr problem (one spot issue is div <= 16 , but in the original
> > > code it was div < 16)?
> >
> > Could you help verify whether the patch fixes you issue?
> >
> > index 1b7de74a72..3347fbe738 100644
> > --- a/drivers/mmc/fsl_esdhc.c
> > +++ b/drivers/mmc/fsl_esdhc.c
> > @@ -640,8 +640,7 @@ static void set_sysctl(struct fsl_esdhc_priv
> > *priv, struct mmc *mmc, uint clock) for (; pre_div < 256; pre_div *=
> > 2) if ((sdhc_clk / pre_div) <= (clock * 16))
> >                                 break;
> > -       } else
> > -               pre_div = 1;
> > +       }
> 
> Please examine this code thoroughly and provide patch.

The pre_div should not override the initialization value at the beginning
of the function.

> 
> The
> } else
> 	pre_div = 1;
> 
> was added there for a purpose, so I'm wondering why it can be easily
> removed now.

The else was wrongly added. It is not correct.

> 
> >
> >         for (div = 1; div <= 16; div++)
> >                 if ((sdhc_clk / (div * pre_div)) <= clock)
> >
> 
> As I've stated above - is the above for() correct?
> 
> In the original code it was div < 16, but here it is div <= 16.

Checking i.MX53 SDHC DVS, it supports [1,16], so should use "<=16", other i.MX has same.

Divisor:
This register is used to provide a more exact divisor to generate the desired SD clock frequency.
NOTE: The divider can even support odd divisor without deterioration of duty cycle.
The setting are as following:
0x0 Divisor by 1
0x1 Divisor by 2
0xe Divisor by 15
0xf Divisor by 16

Regards,
Peng.

> 
> >
> > Thanks,
> > Peng.
> >
> > >
> > > > >
> > > > > Thanks,
> > > > > Peng.
> > > > >
> > > > > >
> > > > > > Signed-off-by: Lukasz Majewski <lukma at denx.de>
> > > > > > ---
> > > > > >  drivers/mmc/fsl_esdhc.c | 23 +++++------------------
> > > > > >  1 file changed, 5 insertions(+), 18 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/mmc/fsl_esdhc.c b/drivers/mmc/fsl_esdhc.c
> > > > > > index 1b7de74a72..377b2673a3 100644
> > > > > > --- a/drivers/mmc/fsl_esdhc.c
> > > > > > +++ b/drivers/mmc/fsl_esdhc.c
> > > > > > @@ -621,31 +621,18 @@ static void set_sysctl(struct
> > > > > > fsl_esdhc_priv *priv, struct mmc *mmc, uint clock)  #else
> > > > > >  	int pre_div = 2;
> > > > > >  #endif
> > > > > > +	int ddr_pre_div = mmc->ddr_mode ? 2 : 1;
> > > > > >  	int sdhc_clk = priv->sdhc_clk;
> > > > > >  	uint clk;
> > > > > >
> > > > > > -	/*
> > > > > > -	 * For ddr mode, usdhc need to enable DDR mode first,
> > > > > > after select
> > > > > > -	 * this DDR mode, usdhc will automatically divide the
> > > > > > usdhc clock
> > > > > > -	 */
> > > > > > -	if (mmc->ddr_mode) {
> > > > > > -		writel(readl(&regs->mixctrl) |
> > > > > > MIX_CTRL_DDREN, &regs->mixctrl);
> > > > > > -		sdhc_clk >>= 1;
> > > > > > -	}
> > > > > > -
> > > > > >  	if (clock < mmc->cfg->f_min)
> > > > > >  		clock = mmc->cfg->f_min;
> > > > > >
> > > > > > -	if (sdhc_clk / 16 > clock) {
> > > > > > -		for (; pre_div < 256; pre_div *= 2)
> > > > > > -			if ((sdhc_clk / pre_div) <= (clock *
> > > > > > 16))
> > > > > > -				break;
> > > > > > -	} else
> > > > > > -		pre_div = 1;
> > > > > > +	while (sdhc_clk / (16 * pre_div * ddr_pre_div) >
> > > > > > clock && pre_div < 256)
> > > > > > +		pre_div *= 2;
> > > > > >
> > > > > > -	for (div = 1; div <= 16; div++)
> > > > > > -		if ((sdhc_clk / (div * pre_div)) <= clock)
> > > > > > -			break;
> > > > > > +	while (sdhc_clk / (div * pre_div * ddr_pre_div) >
> > > > > > clock && div < 16)
> > > > > > +		div++;
> > > > > >
> > > > > >  	pre_div >>= 1;
> > > > > >  	div -= 1;
> > > > > > --
> > > > > > 2.11.0
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > > Best regards,
> > > >
> > > > Lukasz Majewski
> > > >
> > > > --
> > > >
> > > > DENX Software Engineering GmbH,      Managing Director: Wolfgang
> > > Denk
> > > > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > > > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > > > lukma at denx.de
> > >
> > >
> > >
> > >
> > > Best regards,
> > >
> > > Lukasz Majewski
> > >
> > > --
> > >
> > > DENX Software Engineering GmbH,      Managing Director: Wolfgang
> > > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > > lukma at denx.de
> 
> 
> 
> 
> Best regards,
> 
> Lukasz Majewski
> 
> --
> 
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> lukma at denx.de

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