Re: [PATCH 1/2] drm/msm/dsi: add a helper method to compute the dsi byte clk

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On 22/09/2022 03:49, Abhinav Kumar wrote:
> Re-arrange the dsi_calc_pclk method to two helpers, one to
> compute the DSI byte clk and the other to compute the pclk.
> 
> This makes the separation of the two clean and also allows
> clients to compute and use the dsi byte clk separately.
> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
> ---
>   drivers/gpu/drm/msm/dsi/dsi.h      |  2 ++
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 27 +++++++++++++++++++--------
>   2 files changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi.h b/drivers/gpu/drm/msm/dsi/dsi.h
> index 2a96b4fe7839..60ba8e67f550 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi.h
> +++ b/drivers/gpu/drm/msm/dsi/dsi.h
> @@ -118,6 +118,8 @@ int dsi_link_clk_enable_6g(struct msm_dsi_host *msm_host);
>   int dsi_link_clk_enable_v2(struct msm_dsi_host *msm_host);
>   void dsi_link_clk_disable_6g(struct msm_dsi_host *msm_host);
>   void dsi_link_clk_disable_v2(struct msm_dsi_host *msm_host);
> +unsigned long dsi_byte_clk_get_rate(struct mipi_dsi_host *host, bool is_bonded_dsi,
> +		const struct drm_display_mode *mode);
>   int dsi_tx_buf_alloc_6g(struct msm_dsi_host *msm_host, int size);
>   int dsi_tx_buf_alloc_v2(struct msm_dsi_host *msm_host, int size);
>   void *dsi_tx_buf_get_6g(struct msm_dsi_host *msm_host);
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 57a4c0fa614b..32b35d4ac1d3 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -569,9 +569,8 @@ void dsi_link_clk_disable_v2(struct msm_dsi_host *msm_host)
>   	clk_disable_unprepare(msm_host->byte_clk);
>   }
>   
> -static unsigned long dsi_get_pclk_rate(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
> +static unsigned long dsi_get_pclk_rate(const struct drm_display_mode *mode, bool is_bonded_dsi)
>   {
> -	struct drm_display_mode *mode = msm_host->mode;
>   	unsigned long pclk_rate;
>   
>   	pclk_rate = mode->clock * 1000;
> @@ -588,12 +587,18 @@ static unsigned long dsi_get_pclk_rate(struct msm_dsi_host *msm_host, bool is_bo
>   	return pclk_rate;
>   }
>   
> -static void dsi_calc_pclk(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
> +unsigned long dsi_byte_clk_get_rate(struct mipi_dsi_host *host, bool is_bonded_dsi,
> +		const struct drm_display_mode *mode)
>   {
> +	struct msm_dsi_host *msm_host = to_msm_dsi_host(host);
>   	u8 lanes = msm_host->lanes;
>   	u32 bpp = dsi_get_bpp(msm_host->format);
> -	unsigned long pclk_rate = dsi_get_pclk_rate(msm_host, is_bonded_dsi);
> -	u64 pclk_bpp = (u64)pclk_rate * bpp;
> +	unsigned long pclk_rate;
> +	u64 pclk_bpp;
> +
> +	pclk_rate = dsi_get_pclk_rate(mode, is_bonded_dsi);
> +
> +	pclk_bpp = (u64)pclk_rate * bpp;

Any particular reason for this? The following patch would be more obvious:

 > -	unsigned long pclk_rate = dsi_get_pclk_rate(msm_host, is_bonded_dsi);
 > +	unsigned long pclk_rate = dsi_get_pclk_rate(mode, is_bonded_dsi);
 >  	u64 pclk_bpp = (u64)pclk_rate * bpp;


>   
>   	if (lanes == 0) {
>   		pr_err("%s: forcing mdss_dsi lanes to 1\n", __func__);
> @@ -606,8 +611,14 @@ static void dsi_calc_pclk(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
>   	else
>   		do_div(pclk_bpp, (8 * lanes));
>   
> -	msm_host->pixel_clk_rate = pclk_rate;
> -	msm_host->byte_clk_rate = pclk_bpp;
> +	return pclk_bpp;
> +}
> +
> +static void dsi_calc_pclk(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
> +{
> +	msm_host->pixel_clk_rate = dsi_get_pclk_rate(msm_host->mode, is_bonded_dsi);
> +	msm_host->byte_clk_rate = dsi_byte_clk_get_rate(&msm_host->base, is_bonded_dsi,
> +			msm_host->mode);
>   
>   	DBG("pclk=%lu, bclk=%lu", msm_host->pixel_clk_rate,
>   				msm_host->byte_clk_rate);
> @@ -635,7 +646,7 @@ int dsi_calc_clk_rate_v2(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
>   
>   	dsi_calc_pclk(msm_host, is_bonded_dsi);
>   
> -	pclk_bpp = (u64)dsi_get_pclk_rate(msm_host, is_bonded_dsi) * bpp;
> +	pclk_bpp = (u64)dsi_get_pclk_rate(msm_host->mode, is_bonded_dsi) * bpp;
>   	do_div(pclk_bpp, 8);
>   	msm_host->src_clk_rate = pclk_bpp;


Following my previous feedback:

I think at this moment msm_host->src_clk_rate = msm_host->byte_clk_rate 
* msm_host->lanes. If so, we can drop dsi_get_pclk_rate() call and the 
multiply/do_div calculation and use the above formula instead.

If this looks logical, could you please prepend a patch changing this?

LGTM otherwise.

-- 
With best wishes
Dmitry