Re: [PATCH 09/11] phy: rockchip-emmc: Set phyctrl_frqsel based on card clock

[Shawn Lin <shawn.lin-TNX95d0MmH7DzftRWevZcw@public.gmane.org>]

On 2016/6/8 6:44, Douglas Anderson wrote:
> The "phyctrl_frqsel" is described in the Arasan datasheet [1] as "the
> frequency range of DLL operation".  Although the Rockchip variant of
> this PHY has different ranges than the reference Arasan PHY it appears
> as if the functionality is similar.  We should set this phyctrl field
> properly.
>
> Note: as per Rockchip engineers, apparently the "phyctrl_frqsel" is
> actually only useful in HS200 / HS400 modes even though the DLL itself
> it used for some purposes in all modes.  See the discussion in the
> earlier change in this series: ("mmc: sdhci-of-arasan: Always power the
> PHY off/on when clock changes").  In any case, it shouldn't hurt to set
> this always.
>
> Note that this change should allow boards to run at HS200 / HS400 speed
> modes while running at 100 MHz or 150 MHz.  In fact, running HS400 at
> 150 MHz (giving 300 MB/s) is the main motivation of this series, since
> performance is still good but signal integrity problems are less
> prevelant at 150 MHz.

Thanks for doing this, but I think we should limit freq if assigning
max-frequency from DT more explicitly since the PHY could only support
50/100/150/200M for hs200/400? Otherwise I can't say if the PHY could
always work well. i.e if geting 125000000 ... 174999999 , you code make
the phyctrl_frqsel to be 150M, so it will be 15% missing of precision
for tuning delay element. Ideally, the sample point should be in the
middle of window, but I don't know if there is a bad HW	design makes
the window small enough which need special care about it.



>
> [1]: https://arasan.com/wp-content/media/eMMC-5-1-Total-Solution_Rev-1-3.pdf
>
> Signed-off-by: Douglas Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> ---
>  drivers/phy/phy-rockchip-emmc.c | 74 +++++++++++++++++++++++++++++++----------
>  1 file changed, 57 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/phy/phy-rockchip-emmc.c b/drivers/phy/phy-rockchip-emmc.c
> index 8336053aea5c..0fce7359d468 100644
> --- a/drivers/phy/phy-rockchip-emmc.c
> +++ b/drivers/phy/phy-rockchip-emmc.c
> @@ -14,6 +14,7 @@
>   * GNU General Public License for more details.
>   */
>
> +#include <linux/clk.h>
>  #include <linux/delay.h>
>  #include <linux/mfd/syscon.h>
>  #include <linux/module.h>
> @@ -78,16 +79,61 @@
>  struct rockchip_emmc_phy {
>  	unsigned int	reg_offset;
>  	struct regmap	*reg_base;
> +	struct clk	*emmcclk;
>  };
>
> -static int rockchip_emmc_phy_power(struct rockchip_emmc_phy *rk_phy,
> -				   bool on_off)
> +static int rockchip_emmc_phy_power(struct phy *phy, bool on_off)
>  {
> +	struct rockchip_emmc_phy *rk_phy = phy_get_drvdata(phy);
>  	unsigned int caldone;
>  	unsigned int dllrdy;
> +	unsigned int freqsel = PHYCTRL_FREQSEL_200M;
>  	unsigned long timeout;
>
>  	/*
> +	 * We purposely get the clock here and not in probe to avoid the
> +	 * circular dependency problem.  We expect:
> +	 * - PHY driver to probe
> +	 * - USB driver to start probe
> +	 * - USB driver to register it's clock
> +	 * - USB driver to get the PHY
> +	 * - USB driver to power on the PHY

USB?

> +	 */
> +	if (!rk_phy->emmcclk) {
> +		rk_phy->emmcclk = devm_clk_get(&phy->dev, "emmcclk");
> +
> +		/* Don't expect defer at this point; try next time */
> +		if (PTR_ERR(rk_phy->emmcclk) == -EPROBE_DEFER) {
> +			dev_warn(&phy->dev, "Unexpected emmcclk defer\n");
> +			rk_phy->emmcclk = NULL;
> +		}
> +	}
> +
> +	if (!IS_ERR_OR_NULL(rk_phy->emmcclk)) {
> +		unsigned long rate = clk_get_rate(rk_phy->emmcclk);
> +
> +		switch (rate) {
> +		case 0 ... 74999999:
> +			/* Nominal  50 MHz */
> +			freqsel = PHYCTRL_FREQSEL_50M;
> +			break;
> +		case 75000000 ... 124999999:
> +			/* Nominal 100 MHz */
> +			freqsel = PHYCTRL_FREQSEL_100M;
> +			break;
> +		case 125000000 ... 174999999:
> +			/* Nominal 150 MHz */
> +			freqsel = PHYCTRL_FREQSEL_150M;
> +			break;
> +		default:
> +			if (rate > 200000000)
> +				dev_warn(&phy->dev, "Unsupported rate: %lu\n",
> +					 rate);
> +			break;
> +		};
> +	}
> +
> +	/*
>  	 * Keep phyctrl_pdb and phyctrl_endll low to allow
>  	 * initialization of CALIO state M/C DFFs
>  	 */
> @@ -132,6 +178,13 @@ static int rockchip_emmc_phy_power(struct rockchip_emmc_phy *rk_phy,
>  		return -ETIMEDOUT;
>  	}
>
> +	/* Set the frequency of the DLL operation */
> +	regmap_write(rk_phy->reg_base,
> +		     rk_phy->reg_offset + GRF_EMMCPHY_CON0,
> +		     HIWORD_UPDATE(freqsel, PHYCTRL_FREQSEL_MASK,
> +				   PHYCTRL_FREQSEL_SHIFT));
> +
> +	/* Turn on the DLL */
>  	regmap_write(rk_phy->reg_base,
>  		     rk_phy->reg_offset + GRF_EMMCPHY_CON6,
>  		     HIWORD_UPDATE(PHYCTRL_ENDLL_ENABLE,
> @@ -167,15 +220,8 @@ static int rockchip_emmc_phy_power(struct rockchip_emmc_phy *rk_phy,
>
>  static int rockchip_emmc_phy_power_off(struct phy *phy)
>  {
> -	struct rockchip_emmc_phy *rk_phy = phy_get_drvdata(phy);
> -	int ret = 0;
> -
>  	/* Power down emmc phy analog blocks */
> -	ret = rockchip_emmc_phy_power(rk_phy, PHYCTRL_PDB_PWR_OFF);
> -	if (ret)
> -		return ret;
> -
> -	return 0;
> +	return rockchip_emmc_phy_power(phy, PHYCTRL_PDB_PWR_OFF);
>  }
>
>  static int rockchip_emmc_phy_power_on(struct phy *phy)
> @@ -183,12 +229,6 @@ static int rockchip_emmc_phy_power_on(struct phy *phy)
>  	struct rockchip_emmc_phy *rk_phy = phy_get_drvdata(phy);
>  	int ret = 0;
>
> -	/* DLL operation: 200 MHz */
> -	regmap_write(rk_phy->reg_base,
> -		     rk_phy->reg_offset + GRF_EMMCPHY_CON0,
> -		     HIWORD_UPDATE(PHYCTRL_FREQSEL_200M,
> -				   PHYCTRL_FREQSEL_MASK,
> -				   PHYCTRL_FREQSEL_SHIFT));
>
>  	/* Drive impedance: 50 Ohm */
>  	regmap_write(rk_phy->reg_base,
> @@ -212,7 +252,7 @@ static int rockchip_emmc_phy_power_on(struct phy *phy)
>  				   PHYCTRL_OTAPDLYSEL_SHIFT));
>
>  	/* Power up emmc phy analog blocks */
> -	ret = rockchip_emmc_phy_power(rk_phy, PHYCTRL_PDB_PWR_ON);
> +	ret = rockchip_emmc_phy_power(phy, PHYCTRL_PDB_PWR_ON);
>  	if (ret)
>  		return ret;
>
>


-- 
Best Regards
Shawn Lin

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