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 <[email protected]>
> > ---
> > .../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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