RE: [PATCH 4/4 v5] ESDHC: Workaround for data crc error on p1010rdb

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Chris,
Thanks.

I will think about how to handle it and rework it.

> -----Original Message-----
> From: Chris Ball [mailto:cjb@xxxxxxxxxx]
> Sent: Sunday, February 05, 2012 6:22 AM
> To: Huang Changming-R66093
> Cc: linux-mmc@xxxxxxxxxxxxxxx; Huang Changming-R66093; Jain Priyanka-
> B32167
> Subject: Re: [PATCH 4/4 v5] ESDHC: Workaround for data crc error on
> p1010rdb
> 
> Hi Jerry,
> 
> On Mon, Jan 16 2012, r66093@xxxxxxxxxxxxx wrote:
> > From: Jerry Huang <Chang-Ming.Huang@xxxxxxxxxxxxx>
> >
> > SD card read was failing (data crc error)on some cards at maximum
> > possible frequency on P1010(CCB frequency set to 400MHz).
> > Some clock deviations are also observed at this frequency.
> > Hence reduced the mmc clock freq.
> >
> > Signed-off-by: Priyanka Jain <Priyanka.Jain@xxxxxxxxxxxxx>
> > Singed-off-by: Jerry Huang <Chang-Ming.Huang@xxxxxxxxxxxxx>
> > CC: Chris Ball <cjb@xxxxxxxxxx>
> > Acked-by: Anton Vorontsov <cbouatmailru@xxxxxxxxx>
> > ---
> > changes for v2:
> > 	- change the property to compatible for quirks changes for v3:
> > 	- fix one compile error
> > changes for v4:
> > 	- use hooks to suspend/resume the special platform changes for v5:
> > 	- add the Acked-by
> >
> >  drivers/mmc/host/sdhci-esdhc.h |    9 ++++++++-
> >  drivers/mmc/host/sdhci-pltfm.c |    3 +++
> >  include/linux/mmc/sdhci.h      |    2 ++
> >  3 files changed, 13 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-esdhc.h
> > b/drivers/mmc/host/sdhci-esdhc.h index b97b2f5..8e00174 100644
> > --- a/drivers/mmc/host/sdhci-esdhc.h
> > +++ b/drivers/mmc/host/sdhci-esdhc.h
> > @@ -1,7 +1,7 @@
> >  /*
> >   * Freescale eSDHC controller driver generics for OF and pltfm.
> >   *
> > - * Copyright (c) 2007 Freescale Semiconductor, Inc.
> > + * Copyright (c) 2007,2011 Freescale Semiconductor, Inc.
> >   * Copyright (c) 2009 MontaVista Software, Inc.
> >   * Copyright (c) 2010 Pengutronix e.K.
> >   *   Author: Wolfram Sang <w.sang@xxxxxxxxxxxxxx>
> > @@ -56,6 +56,13 @@ static inline void esdhc_set_clock(struct sdhci_host
> *host, unsigned int clock)
> >  	if (clock == 0)
> >  		goto out;
> >
> > +	if (host->quirks2 & SDHCI_QUIRK2_RELAX_FREQ) {
> > +		if (clock > 20000000)
> > +			clock -= 5000000;
> > +		if (clock > 40000000)
> > +			clock -= 5000000;
> > +	}
> > +
> >  	while (host->max_clk / pre_div / 16 > clock && pre_div < 256)
> >  		pre_div *= 2;
> >
> > diff --git a/drivers/mmc/host/sdhci-pltfm.c
> > b/drivers/mmc/host/sdhci-pltfm.c index 04fa130..c932316 100644
> > --- a/drivers/mmc/host/sdhci-pltfm.c
> > +++ b/drivers/mmc/host/sdhci-pltfm.c
> > @@ -81,6 +81,9 @@ void sdhci_get_of_property(struct platform_device
> *pdev)
> >  					"fsl,mpc8536-esdhc"))
> >  			host->quirks |= SDHCI_QUIRK_BROKEN_TIMEOUT_VAL;
> >
> > +		if (of_device_is_compatible(np, "fsl,p1010-esdhc"))
> > +			host->quirks2 |= SDHCI_QUIRK2_RELAX_FREQ;
> > +
> >  		clk = of_get_property(np, "clock-frequency", &size);
> >  		if (clk && size == sizeof(*clk) && *clk)
> >  			pltfm_host->clock = be32_to_cpup(clk); diff --git
> > a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h index
> > e4b6935..f7c1e13 100644
> > --- a/include/linux/mmc/sdhci.h
> > +++ b/include/linux/mmc/sdhci.h
> > @@ -91,6 +91,8 @@ struct sdhci_host {
> >  	unsigned int quirks2;	/* More deviations from spec. */
> >
> >  #define SDHCI_QUIRK2_OWN_CARD_DETECTION			(1<<0)
> > +/* Controller operates the cards at reduced frequency */
> > +#define SDHCI_QUIRK2_RELAX_FREQ				(1<<1)
> >
> >  	int irq;		/* Device IRQ */
> >  	void __iomem *ioaddr;	/* Mapped address */
> 
> I don't think this should be implemented as a global SDHCI quirk, because
> I don't think it's ever going to be used on non-ESDHC hardware.
> Since you're already handling the clock change in an esdhc-only function,
> can you just use your "fsl,p1010-esdhc" test to set some driver-local
> flag to use later, instead of involving sdhci.h?
> 
> Thanks.  (No need to resend the other patches, I'll take this one
> separately when it's been reworked.)
> 
> - Chris.
> --
> Chris Ball   <cjb@xxxxxxxxxx>   <http://printf.net/>
> One Laptop Per Child


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