[PATCH v2 5/8] mmc: sdhci-esdhc-imx: add delay line setting support

[Shawn Guo]

On Fri, Oct 18, 2013 at 06:54:18PM +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      |    5 +++++
>  drivers/mmc/host/sdhci-esdhc-imx.c                 |   18 ++++++++++++++++++
>  include/linux/platform_data/mmc-esdhc-imx.h        |    1 +
>  3 files changed, 24 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..78a45c5 100644
> --- a/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
> +++ b/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
> @@ -12,6 +12,11 @@ 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 the number of delay cells for override mode.
> +  This is used to set the clock delay for DLL(Delay Line) on override mode
> +  to select a proper data sampling window in case the clock quality is not good
> +  due to signal path is too long on the board.
> +  please refer to DLL chapter in RM for details.

It might be better to reword it like:

Please refer to eSDHC/uSDHC DLL_CTRL register bit field
DLL_CTRL_SLV_OVERRIDE_VAL in Reference Manual for details.

>  
>  Examples:
>  
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index c5c26bd..87d202b 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
> @@ -817,6 +822,7 @@ 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:
> @@ -837,6 +843,15 @@ 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;
> +			writel(v, host->ioaddr + ESDHC_DLL_CTRL);
> +		}
>  		break;
>  	}
>  
> @@ -901,6 +916,9 @@ 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
> 
>