Re: [v3 3/3] drm/msm/dsi: Add 10nm dsi phy tuning configuration support

[Dmitry Baryshkov]

On 18/01/2022 23:38, Rajeev Nandan wrote:
> The clock and data lanes of the DSI PHY have a calibration circuitry
> feature. As per the MSM DSI PHY tuning guidelines, the drive strength
> tuning can be done by adjusting rescode offset for hstop/hsbot, and
> the drive level tuning can be done by adjusting the LDO output level
> for the HSTX drive.
>
> Signed-off-by: Rajeev Nandan <quic_rajeevny@xxxxxxxxxxx>
> ---
>
> Changes in v2:
>   - Split into generic code and 10nm-specific part (Dmitry Baryshkov)
>   - Fix the backward compatibility (Dmitry Baryshkov)
>
> Changes in v3:
>   - Address comments for phy tuning data structure (Dmitry Baryshkov)
>   - Make changes as per updated dt-bindings
>
>
>   drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c | 97 ++++++++++++++++++++++++++++--
>   1 file changed, 91 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c
> index d8128f5..2d225fb 100644
> --- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c
> +++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c
> @@ -83,6 +83,18 @@ struct dsi_pll_10nm {
>   
>   #define to_pll_10nm(x)	container_of(x, struct dsi_pll_10nm, clk_hw)
>   
> +/**
> + * struct dsi_phy_10nm_tuning_cfg - Holds 10nm PHY tuning config parameters.
> + * @rescode_offset_top: Offset for pull-up legs rescode.
> + * @rescode_offset_bot: Offset for pull-down legs rescode.
> + * @vreg_ctrl: vreg ctrl to drive LDO level
> + */
> +struct dsi_phy_10nm_tuning_cfg {
> +	u8 rescode_offset_top[DSI_LANE_MAX];
> +	u8 rescode_offset_bot[DSI_LANE_MAX];
> +	u8 vreg_ctrl;
> +};
> +
>   /*
>    * Global list of private DSI PLL struct pointers. We need this for bonded DSI
>    * mode, where the master PLL's clk_ops needs access the slave's private data
> @@ -747,6 +759,7 @@ static void dsi_phy_hw_v3_0_lane_settings(struct msm_dsi_phy *phy)
>   	int i;
>   	u8 tx_dctrl[] = { 0x00, 0x00, 0x00, 0x04, 0x01 };
>   	void __iomem *lane_base = phy->lane_base;
> +	struct dsi_phy_10nm_tuning_cfg *tuning_cfg = phy->tuning_cfg;
>   
>   	if (phy->cfg->quirks & DSI_PHY_10NM_QUIRK_OLD_TIMINGS)
>   		tx_dctrl[3] = 0x02;
> @@ -775,10 +788,13 @@ static void dsi_phy_hw_v3_0_lane_settings(struct msm_dsi_phy *phy)
>   		dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_CFG2(i), 0x0);
>   		dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_CFG3(i),
>   			      i == 4 ? 0x80 : 0x0);
> -		dsi_phy_write(lane_base +
> -			      REG_DSI_10nm_PHY_LN_OFFSET_TOP_CTRL(i), 0x0);
> -		dsi_phy_write(lane_base +
> -			      REG_DSI_10nm_PHY_LN_OFFSET_BOT_CTRL(i), 0x0);
> +
> +		/* platform specific dsi phy drive strength adjustment */
> +		dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_OFFSET_TOP_CTRL(i),
> +				tuning_cfg->rescode_offset_top[i]);
> +		dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_OFFSET_BOT_CTRL(i),
> +				tuning_cfg->rescode_offset_bot[i]);
> +
>   		dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_TX_DCTRL(i),
>   			      tx_dctrl[i]);
>   	}
> @@ -799,6 +815,7 @@ static int dsi_10nm_phy_enable(struct msm_dsi_phy *phy,
>   	u32 const timeout_us = 1000;
>   	struct msm_dsi_dphy_timing *timing = &phy->timing;
>   	void __iomem *base = phy->base;
> +	struct dsi_phy_10nm_tuning_cfg *tuning_cfg = phy->tuning_cfg;
>   	u32 data;
>   
>   	DBG("");
> @@ -834,8 +851,9 @@ static int dsi_10nm_phy_enable(struct msm_dsi_phy *phy,
>   	/* Select MS1 byte-clk */
>   	dsi_phy_write(base + REG_DSI_10nm_PHY_CMN_GLBL_CTRL, 0x10);
>   
> -	/* Enable LDO */
> -	dsi_phy_write(base + REG_DSI_10nm_PHY_CMN_VREG_CTRL, 0x59);
> +	/* Enable LDO with platform specific drive level/amplitude adjustment */
> +	dsi_phy_write(base + REG_DSI_10nm_PHY_CMN_VREG_CTRL,
> +		      tuning_cfg->vreg_ctrl);
>   
>   	/* Configure PHY lane swap (TODO: we need to calculate this) */
>   	dsi_phy_write(base + REG_DSI_10nm_PHY_CMN_LANE_CFG0, 0x21);
> @@ -922,6 +940,71 @@ static void dsi_10nm_phy_disable(struct msm_dsi_phy *phy)
>   	DBG("DSI%d PHY disabled", phy->id);
>   }
>   
> +static int dsi_10nm_phy_parse_dt(struct msm_dsi_phy *phy)
> +{
> +	struct device *dev = &phy->pdev->dev;
> +	struct dsi_phy_10nm_tuning_cfg *tuning_cfg;
> +	u8 offset_top[DSI_LANE_MAX] = { 0 }; /* No offset */
> +	u8 offset_bot[DSI_LANE_MAX] = { 0 }; /* No offset */
> +	u32 ldo_level = 400; /* 400mV */
> +	u8 level;
> +	int ret, i;
> +
> +	tuning_cfg = devm_kzalloc(dev, sizeof(*tuning_cfg), GFP_KERNEL);
> +	if (!tuning_cfg)
> +		return -ENOMEM;
> +
> +	/* Drive strength adjustment parameters */
> +	ret = of_property_read_u8_array(dev->of_node, "qcom,phy-rescode-offset-top",
> +					offset_top, DSI_LANE_MAX);
> +	if (ret && ret != -EINVAL)
> +		DRM_DEV_ERROR(dev, "failed to parse qcom,phy-rescode-offset-top, %d\n", ret);
> +
> +	for (i = 0; i < DSI_LANE_MAX; i++)
> +		tuning_cfg->rescode_offset_top[i] = 0x3f & offset_top[i];

You should validate offset_top and offset_bot to be withing expected 
ranges and return an error otherwise.

> +
> +	ret = of_property_read_u8_array(dev->of_node, "qcom,phy-rescode-offset-bot",
> +					offset_bot, DSI_LANE_MAX);
> +	if (ret && ret != -EINVAL)
> +		DRM_DEV_ERROR(dev, "failed to parse qcom,phy-rescode-offset-bot, %d\n", ret);
> +
> +	for (i = 0; i < DSI_LANE_MAX; i++)
> +		tuning_cfg->rescode_offset_bot[i] = 0x3f & offset_bot[i];
> +
> +	/* Drive level/amplitude adjustment parameters */
> +	ret = of_property_read_u32(dev->of_node, "qcom,phy-drive-ldo-level", &ldo_level);
> +	if (ret && ret != -EINVAL)
> +		DRM_DEV_ERROR(dev, "failed to parse qcom,phy-drive-ldo-level, %d\n", ret);
> +
> +	switch (ldo_level) {
> +	case 375:
> +		level = 0;
> +		break;
> +	case 400:
> +		level = 1;
> +		break;
> +	case 425:
> +		level = 2;
> +		break;
> +	case 450:
> +		level = 3;
> +		break;
> +	case 475:
> +		level = 4;
> +		break;
> +	case 500:
> +		level = 5;
> +		break;
> +	default:
> +		level = 1; /* 400mV */

Please change to:
dev_err(....);
return -EINVAL;

> +	}
> +	tuning_cfg->vreg_ctrl = 0x58 | (0x7 & level);
> +
> +	phy->tuning_cfg = tuning_cfg;
> +
> +	return 0;
> +}
> +
>   const struct msm_dsi_phy_cfg dsi_phy_10nm_cfgs = {
>   	.has_phy_lane = true,
>   	.reg_cfg = {
> @@ -936,6 +1019,7 @@ const struct msm_dsi_phy_cfg dsi_phy_10nm_cfgs = {
>   		.pll_init = dsi_pll_10nm_init,
>   		.save_pll_state = dsi_10nm_pll_save_state,
>   		.restore_pll_state = dsi_10nm_pll_restore_state,
> +		.parse_dt_properties = dsi_10nm_phy_parse_dt,
>   	},
>   	.min_pll_rate = 1000000000UL,
>   	.max_pll_rate = 3500000000UL,
> @@ -957,6 +1041,7 @@ const struct msm_dsi_phy_cfg dsi_phy_10nm_8998_cfgs = {
>   		.pll_init = dsi_pll_10nm_init,
>   		.save_pll_state = dsi_10nm_pll_save_state,
>   		.restore_pll_state = dsi_10nm_pll_restore_state,
> +		.parse_dt_properties = dsi_10nm_phy_parse_dt,
>   	},
>   	.min_pll_rate = 1000000000UL,
>   	.max_pll_rate = 3500000000UL,


--
With best wishes
Dmitry