[PATCH RFC 5/5] drm/msm/dsi: Use MSM and DRM DSC helper methods

[Jessica Zhang]

On 3/30/2023 4:14 PM, Dmitry Baryshkov wrote:
> On 31/03/2023 01:49, Jessica Zhang wrote:
>>
>>
>> On 3/29/2023 4:48 PM, Dmitry Baryshkov wrote:
>>> On 30/03/2023 02:18, Jessica Zhang wrote:
>>>> Use MSM and DRM DSC helper methods.
>>>>
>>>> Signed-off-by: Jessica Zhang <quic_jesszhan at quicinc.com>
>>>> ---
>>>>   drivers/gpu/drm/msm/dsi/dsi_host.c | 18 ++++++++++++------
>>>>   1 file changed, 12 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c 
>>>> b/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>> index 74d38f90398a..7419fe58a941 100644
>>>> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>> @@ -31,6 +31,7 @@
>>>>   #include "msm_kms.h"
>>>>   #include "msm_gem.h"
>>>>   #include "phy/dsi_phy.h"
>>>> +#include "disp/msm_dsc_helper.h"
>>>>   #define DSI_RESET_TOGGLE_DELAY_MS 20
>>>> @@ -841,14 +842,14 @@ static void dsi_update_dsc_timing(struct 
>>>> msm_dsi_host *msm_host, bool is_cmd_mod
>>>>   {
>>>>       struct drm_dsc_config *dsc = msm_host->dsc;
>>>>       u32 reg, reg_ctrl, reg_ctrl2;
>>>> -    u32 slice_per_intf, total_bytes_per_intf;
>>>> +    u32 slice_per_intf;
>>>>       u32 pkt_per_line;
>>>>       u32 eol_byte_num;
>>>>       /* first calculate dsc parameters and then program
>>>>        * compress mode registers
>>>>        */
>>>> -    slice_per_intf = DIV_ROUND_UP(hdisplay, dsc->slice_width);
>>>> +    slice_per_intf = msm_dsc_get_slice_per_intf(dsc, hdisplay);
>>>
>>> This looks good
>>>
>>>>       /*
>>>>        * If slice_count is greater than slice_per_intf
>>>> @@ -858,10 +859,10 @@ static void dsi_update_dsc_timing(struct 
>>>> msm_dsi_host *msm_host, bool is_cmd_mod
>>>>       if (dsc->slice_count > slice_per_intf)
>>>>           dsc->slice_count = 1;
>>>> -    total_bytes_per_intf = dsc->slice_chunk_size * slice_per_intf;
>>>> +    eol_byte_num = msm_dsc_get_eol_byte_num(msm_host->dsc, hdisplay,
>>>> +            dsi_get_bpp(msm_host->format));
>>>> -    eol_byte_num = total_bytes_per_intf % 3;
>>>> -    pkt_per_line = slice_per_intf / dsc->slice_count;
>>>> +    pkt_per_line = slice_per_intf / MSM_DSC_SLICE_PER_PKT;
>>>
>>> And for these values the result is definitely changed. Separate patch 
>>> & description please. Just in case, "values per downstream kernel" is 
>>> not a proper description for such changes.
>>
>> Hi Dmitry,
>>
>> Sure, I can put this into a separate patch.
>>
>> The reason this was changed from slice_count to SLICE_PER_PKT was 
>> because slice count and slice per packet aren't always equivalent. 
>> There can be cases where panel configures DSC to have multiple soft 
>> slices per interface, but the panel only specifies 1 slice per packet.
> 
> Please put this nice description into the commit message. It is exactly 
> what I was looking for!
> 
> BTW: Do you expect to change MSM_DSC_SLICE_PER_PKT later or it will stay 
> at "1"? If so, it might be easier to drop it and instead add a comment.

MSM_DSC_SLICE_PER_PKT is the default value for panels that don't specify 
a slice_per_pkt value. (Now that I think about it, might be better to 
call it MSM_DSC_DEFAULT_SLICE_PER_PKT instead...)

I don't expect it to change in the future, but it's a little more 
readable than just dividing by 1 IMO. If you prefer dropping the macro 
and adding a comment, I'm also okay with that.

Thanks,

Jessica Zhang

> 
> Regarding eol_byte_num, probably the best explanation would be that is 
> is a size of a padding rather than a size of a trailer bytes in a line 
> (and thus original calculation was incorrect).
> 
>>
>>>
>>>>       if (is_cmd_mode) /* packet data type */
>>>>           reg = 
>>>> DSI_COMMAND_COMPRESSION_MODE_CTRL_STREAM0_DATATYPE(MIPI_DSI_DCS_LONG_WRITE);
>>>> @@ -911,6 +912,11 @@ static void dsi_timing_setup(struct 
>>>> msm_dsi_host *msm_host, bool is_bonded_dsi)
>>>>       DBG("");
>>>> +    if (msm_host->mode_flags & MIPI_DSI_MODE_VIDEO)
>>>> +        /* Default widebus_en to false for now. */
>>>> +        hdisplay = msm_dsc_get_pclk_per_line(msm_host->dsc, 
>>>> mode->hdisplay,
>>>> +                dsi_get_bpp(msm_host->format));
>>>> +
>>>
>>> This is definitely something new and thus should probably go into a 
>>> separate patch and be described. Also I'm not sure how does that 
>>> interact with the hdisplay-related calculations below, under the 
>>> if(dsc) clause.
>>
>> After double-checking the math here, I think this part of the change 
>> is actually wrong. pclk_per_line is essentially doing hdisplay / 3, 
>> which is a repeat of what's being done in the `if (dsc)` block.
>>
>> Will replace `hdisplay /= 3` with the pclk_per_line calculation.
> 
> Thanks!
> 
>>
>> Thanks,
>>
>> Jessica Zhang
>>
>>>
>>>>       /*
>>>>        * For bonded DSI mode, the current DRM mode has
>>>>        * the complete width of the panel. Since, the complete
>>>> @@ -1759,7 +1765,7 @@ static int dsi_populate_dsc_params(struct 
>>>> msm_dsi_host *msm_host, struct drm_dsc
>>>>           return ret;
>>>>       }
>>>> -    dsc->initial_scale_value = 32;
>>>> +    dsc->initial_scale_value = 
>>>> drm_dsc_calculate_initial_scale_value(dsc);
>>>
>>> This is fine, we only support 8bpp where these values match.
>>>
>>>>       dsc->line_buf_depth = dsc->bits_per_component + 1;
>>>>       return drm_dsc_compute_rc_parameters(dsc);
>>>>
>>>
>>> -- 
>>> With best wishes
>>> Dmitry
>>>
> 
> -- 
> With best wishes
> Dmitry
>