drm/msm/dsi: correct byte intf clock rate for 14nm DSI PHY

[Konrad Dybcio]

On 18.01.2023 14:00, Dmitry Baryshkov wrote:
> According to the vendor kernel, byte intf clock rate should be a half of
> the byte clock only when DSI PHY version is above 2.0 (in other words,
> 10nm PHYs and later) and only if PHY is used in D-PHY mode. Currently
> MSM DSI code handles only the second part of the clause (C-PHY vs
> D-PHY), skipping DSI PHY version check, which causes issues on some of
> 14nm DSI PHY platforms (e.g. qcm2290).
> 
> Move divisor selection to DSI PHY code, pass selected divisor through
> shared timings and set byte intf clock rate accordingly.
> 
> Cc: Loic Poulain <loic.poulain at linaro.org>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> ---
> 
> This patch is a reimplementation of [1] in a slightly more flexible way.
> 
> [1] https://patchwork.kernel.org/project/linux-arm-msm/patch/1642586079-12472-1-git-send-email-loic.poulain@linaro.org/
> 
> ---
Tested-by: Konrad Dybcio <konrad.dybcio at linaro.org> # SM6115P J606F
Reviewed-by: Konrad Dybcio <konrad.dybcio at linaro.org>

Interestingly enough, this seems to somehow solve the issue
where I had to manually set the brightness again after the
first frame transfer or get a black screen otherwise.. 

Konrad
>  drivers/gpu/drm/msm/dsi/dsi.h         |  1 +
>  drivers/gpu/drm/msm/dsi/dsi_host.c    | 14 ++++++--------
>  drivers/gpu/drm/msm/dsi/phy/dsi_phy.c |  4 ++++
>  3 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi.h b/drivers/gpu/drm/msm/dsi/dsi.h
> index 1a551cc0e889..bd3763a5d723 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi.h
> +++ b/drivers/gpu/drm/msm/dsi/dsi.h
> @@ -141,6 +141,7 @@ struct msm_dsi_phy_shared_timings {
>  	u32 clk_post;
>  	u32 clk_pre;
>  	bool clk_pre_inc_by_2;
> +	bool byte_intf_clk_div_2;
>  };
>  
>  struct msm_dsi_phy_clk_request {
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 7c21f2fba520..18fa30e1e858 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -122,6 +122,7 @@ struct msm_dsi_host {
>  	struct clk *byte_intf_clk;
>  
>  	unsigned long byte_clk_rate;
> +	unsigned long byte_intf_clk_rate;
>  	unsigned long pixel_clk_rate;
>  	unsigned long esc_clk_rate;
>  
> @@ -398,7 +399,6 @@ int msm_dsi_runtime_resume(struct device *dev)
>  
>  int dsi_link_clk_set_rate_6g(struct msm_dsi_host *msm_host)
>  {
> -	unsigned long byte_intf_rate;
>  	int ret;
>  
>  	DBG("Set clk rates: pclk=%d, byteclk=%lu",
> @@ -418,13 +418,7 @@ int dsi_link_clk_set_rate_6g(struct msm_dsi_host *msm_host)
>  	}
>  
>  	if (msm_host->byte_intf_clk) {
> -		/* For CPHY, byte_intf_clk is same as byte_clk */
> -		if (msm_host->cphy_mode)
> -			byte_intf_rate = msm_host->byte_clk_rate;
> -		else
> -			byte_intf_rate = msm_host->byte_clk_rate / 2;
> -
> -		ret = clk_set_rate(msm_host->byte_intf_clk, byte_intf_rate);
> +		ret = clk_set_rate(msm_host->byte_intf_clk, msm_host->byte_intf_clk_rate);
>  		if (ret) {
>  			pr_err("%s: Failed to set rate byte intf clk, %d\n",
>  			       __func__, ret);
> @@ -2394,6 +2388,10 @@ int msm_dsi_host_power_on(struct mipi_dsi_host *host,
>  		goto unlock_ret;
>  	}
>  
> +	msm_host->byte_intf_clk_rate = msm_host->byte_clk_rate;
> +	if (phy_shared_timings->byte_intf_clk_div_2)
> +		msm_host->byte_intf_clk_rate /= 2;
> +
>  	msm_dsi_sfpb_config(msm_host, true);
>  
>  	ret = regulator_bulk_enable(msm_host->cfg_hnd->cfg->num_regulators,
> diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy.c
> index 57445a5dc816..bb09cbe8ff86 100644
> --- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy.c
> +++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy.c
> @@ -350,6 +350,8 @@ int msm_dsi_dphy_timing_calc_v3(struct msm_dsi_dphy_timing *timing,
>  		timing->shared_timings.clk_pre_inc_by_2 = 0;
>  	}
>  
> +	timing->shared_timings.byte_intf_clk_div_2 = true;
> +
>  	timing->ta_go = 3;
>  	timing->ta_sure = 0;
>  	timing->ta_get = 4;
> @@ -454,6 +456,8 @@ int msm_dsi_dphy_timing_calc_v4(struct msm_dsi_dphy_timing *timing,
>  	tmax = 255;
>  	timing->shared_timings.clk_pre = DIV_ROUND_UP((tmax - tmin) * 125, 10000) + tmin;
>  
> +	timing->shared_timings.byte_intf_clk_div_2 = true;
> +
>  	DBG("%d, %d, %d, %d, %d, %d, %d, %d, %d, %d",
>  		timing->shared_timings.clk_pre, timing->shared_timings.clk_post,
>  		timing->clk_zero, timing->clk_trail, timing->clk_prepare, timing->hs_exit,
>