[PATCH 07/10] mmc: sdhci-esdhc-imx: add delay line setting support

[Dong Aisheng]

On Tue, Oct 15, 2013 at 03:37:06PM +0800, Shawn Guo wrote:
> On Wed, Oct 09, 2013 at 07:20:13PM +0800, Dong Aisheng wrote:
> > The DLL(Delay Line) is newly added to assist in sampling read data.
> > The DLL provides the ability to programmatically select a quantized
> > delay (in fractions of the clock period) regardless of on-chip variations
> > such as process, voltage and temperature (PVT).
> > 
> > This patch adds a user interface to set slave delay line via device tree.
> > It's usually used in high speed mode like mmc DDR mode when the signal
> > quality is not good caused by board design, e.g. the signal path is too long.
> > User can manual set delay line to find a suitable data sampling window
> > for card to work properly.
> > 
> > Signed-off-by: Dong Aisheng <b29396 at freescale.com>
> > ---
> >  .../devicetree/bindings/mmc/fsl-imx-esdhc.txt      |    1 +
> >  drivers/mmc/host/sdhci-esdhc-imx.c                 |   18 ++++++++++++++++++
> >  include/linux/platform_data/mmc-esdhc-imx.h        |    1 +
> >  3 files changed, 20 insertions(+), 0 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt b/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
> > index 1dd6225..ebd3ff5 100644
> > --- a/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
> > +++ b/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
> > @@ -12,6 +12,7 @@ Required properties:
> >  Optional properties:
> >  - fsl,cd-controller : Indicate to use controller internal card detection
> >  - fsl,wp-controller : Indicate to use controller internal write protection
> > +- fsl,delay-line : Specify delay line value of manual override for slave delay.
> 
> It needs more documentation and should refer to the register bits in RM.
> Otherwise, I hardly think people will understand what it is.
> 

Ok, i could improve it a bit.
But user may still need refer to spec to know the details.

> >  
> >  Examples:
> >  
> > diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> > index b6ae5c1..91b2d85 100644
> > --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> > +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> > @@ -46,6 +46,11 @@
> >  /* Bits 3 and 6 are not SDHCI standard definitions */
> >  #define  ESDHC_MIX_CTRL_SDHCI_MASK	0xb7
> >  
> > +/* dll control register */
> > +#define ESDHC_DLL_CTRL			0x60
> > +#define ESDHC_DLL_OVERRIDE_VAL_SHIFT	9
> > +#define ESDHC_DLL_OVERRIDE_EN_SHIFT	8
> > +
> >  /* tune control register */
> >  #define ESDHC_TUNE_CTRL_STATUS		0x68
> >  #define  ESDHC_TUNE_CTRL_STEP		1
> > @@ -803,6 +808,7 @@ static int esdhc_set_uhs_signaling(struct sdhci_host *host, unsigned int uhs)
> >  {
> >  	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> >  	struct pltfm_imx_data *imx_data = pltfm_host->priv;
> > +	struct esdhc_platform_data *boarddata = &imx_data->boarddata;
> >  
> >  	switch (uhs) {
> >  	case MMC_TIMING_UHS_SDR12:
> > @@ -823,6 +829,15 @@ static int esdhc_set_uhs_signaling(struct sdhci_host *host, unsigned int uhs)
> >  				ESDHC_MIX_CTRL_DDREN,
> >  				host->ioaddr + ESDHC_MIX_CTRL);
> >  		imx_data->is_ddr = 1;
> > +		if (boarddata->delay_line) {
> > +			u32 v;
> > +			v = boarddata->delay_line <<
> > +				ESDHC_DLL_OVERRIDE_VAL_SHIFT |
> > +				(1 << ESDHC_DLL_OVERRIDE_EN_SHIFT);
> > +			if (is_imx53_esdhc(imx_data))
> > +				v <<= 1;
> 
> Is the patch (series) tested on imx53?  Or is it just a note that imx53
> has different bit position? 

Only tested on imx6sl.
mx53 register offset is differet.

> 
> > +			writel(v, host->ioaddr + ESDHC_DLL_CTRL);
> 
> Is it safe to always write other bits as zero?

Right, for the feature this patch added, only OVERRIDE_VAL need to set.

Regards
Dong Aisheng

> 
> Shawn
> 
> > +		}
> >  		break;
> >  	}
> >  
> > @@ -887,6 +902,9 @@ sdhci_esdhc_imx_probe_dt(struct platform_device *pdev,
> >  	else
> >  		boarddata->support_vsel = true;
> >  
> > +	if (of_property_read_u32(np, "fsl,delay-line", &boarddata->delay_line))
> > +		boarddata->delay_line = 0;
> > +
> >  	return 0;
> >  }
> >  #else
> > diff --git a/include/linux/platform_data/mmc-esdhc-imx.h b/include/linux/platform_data/mmc-esdhc-imx.h
> > index a0f5a8f..75f70f6 100644
> > --- a/include/linux/platform_data/mmc-esdhc-imx.h
> > +++ b/include/linux/platform_data/mmc-esdhc-imx.h
> > @@ -45,5 +45,6 @@ struct esdhc_platform_data {
> >  	int max_bus_width;
> >  	unsigned int f_max;
> >  	bool support_vsel;
> > +	unsigned int delay_line;
> >  };
> >  #endif /* __ASM_ARCH_IMX_ESDHC_H */
> > -- 
> > 1.7.2.rc3
> > 
> > 
> > --
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