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

[Abhinav Kumar]

On 1/9/2023 5:34 PM, Dmitry Baryshkov wrote:
> 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 at 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.
> 

 From what I see msm_host->src_clk_rate = pixel_clk * bpp / 8;

 From where did you get the above formula?

I just felt that by having two APIs the next patch becomes easier 
because I need to just invoke the API which calculates byte clk.

> If this looks logical, could you please prepend a patch changing this?
> 
> LGTM otherwise.
>