RE: [PATCHv6 1/5] mmc: dw_mmc: Add support to set the SDR and DDR timing through clock framework

[Seungwon Jeon <tgih.jun@samsung.com>]

On Friday, December 13, 2013, Dinh Nguyen wrote:
> From: Dinh Nguyen <dinguyen@altera.com>
> 
> All implementations of the Synopsys DW SD/MMC IP have settings to control
> the phase shift of the CIU clk. These phase shift settings are necessary for
> the SD/MMC to correctly clock the card. All variants of the dw_mmc will need
> these settings, but how they are implemented can vastly vary.
> 
> This patch enables the setting for the SDR and/or DDR settings through the
> common clock framework.
> 
> Depends on the patch "mmc: dw_mmc: Enable the hold reg for certain speed modes",
> that is already reading the "samsung,dw-mshc-sdr-timing" and
> "samsung,dw-mshc-ddr-timing" bindings, this patch saves those values into a
> u32 bitmask that can be passed to the clock framework to use.

I didn't understand this patch.
As you mentioned, clock implementation can be different each SOC.
And what is the difference with existing ciu clock?

> 
> Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
> ---
> v6: Add this patch
> v5: none
> v4: none
> v3: none
> v2: none
> ---
>  drivers/mmc/host/dw_mmc.c  |   23 +++++++++++++++++++++++
>  include/linux/mmc/dw_mmc.h |    6 ++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 480dafe..1fb5cff 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -2431,6 +2431,8 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
>  	if ((sdr_timing[1] == 0) || (ddr_timing[1] == 0))
>  		pdata->cclk_in_drv = 0;
> 
> +	pdata->sdr_timing = (sdr_timing[1] | (sdr_timing[0] << 4));
> +	pdata->ddr_timing = (ddr_timing[1] | (ddr_timing[0] << 4));
Can you explain what it is for?

Thanks,
Seungwon

>  	return pdata;
>  }
> 
> @@ -2478,6 +2480,27 @@ int dw_mci_probe(struct dw_mci *host)
>  		dev_dbg(host->dev, "ciu clock not available\n");
>  		host->bus_hz = host->pdata->bus_hz;
>  	} else {
> +		/* If the CIU clk is available, we check for SDR and DDR
> +		 * timing phase shift settings. But not all platforms
> +		 * may have populated these settings, the driver will not fail
> +		 * if these settings are not specified.
> +		 */
> +		if (host->pdata->sdr_timing) {
> +			host->sdr_clk = devm_clk_get(host->dev, "sdr_mmc_clk");
> +			if (IS_ERR(host->sdr_clk))
> +				dev_dbg(host->dev, "sdr_mmc clock not available\n");
> +			else
> +				clk_set_rate(host->sdr_clk, host->pdata->sdr_timing);
> +		}
> +
> +		if (host->pdata->ddr_timing) {
> +			host->ddr_clk = devm_clk_get(host->dev, "ddr_mmc_clk");
> +			if (IS_ERR(host->ddr_clk))
> +				dev_dbg(host->dev, "ddr_mmc clock not available\n");
> +			else
> +				clk_set_rate(host->ddr_clk, host->pdata->ddr_timing);
> +		}
> +
>  		ret = clk_prepare_enable(host->ciu_clk);
>  		if (ret) {
>  			dev_err(host->dev, "failed to enable ciu clock\n");
> diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
> index 2b5b8bf..ad90ad1 100644
> --- a/include/linux/mmc/dw_mmc.h
> +++ b/include/linux/mmc/dw_mmc.h
> @@ -83,6 +83,8 @@ struct mmc_data;
>   * @priv: Implementation defined private data.
>   * @biu_clk: Pointer to bus interface unit clock instance.
>   * @ciu_clk: Pointer to card interface unit clock instance.
> + * @sdr_clk: Pointer to the SDR clock instance.
> + * @ddr_clk: Pointer to the DDR clock instance.
>   * @slot: Slots sharing this MMC controller.
>   * @fifo_depth: depth of FIFO.
>   * @data_shift: log2 of FIFO item size.
> @@ -170,6 +172,8 @@ struct dw_mci {
>  	void			*priv;
>  	struct clk		*biu_clk;
>  	struct clk		*ciu_clk;
> +	struct clk		*sdr_clk;
> +	struct clk		*ddr_clk;
>  	struct dw_mci_slot	*slot[MAX_MCI_SLOTS];
> 
>  	/* FIFO push and pull */
> @@ -241,6 +245,8 @@ struct dw_mci_board {
>  	u32 caps2;	/* More capabilities */
>  	u32 pm_caps;	/* PM capabilities */
>  	u32 cclk_in_drv;	/*cclk_in_drv phase shift */
> +	u32 sdr_timing;	/* Single data rate timing setting. */
> +	u32 ddr_timing;	/* Double data rate timing setting. */
>  	/*
>  	 * Override fifo depth. If 0, autodetect it from the FIFOTH register,
>  	 * but note that this may not be reliable after a bootloader has used
> --
> 1.7.9.5
> 
> 
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