On 9.05.2023 01:27, Dmitry Baryshkov wrote:
> On 08/05/2023 23:09, Abhinav Kumar wrote:
>>
>>
>> On 5/3/2023 1:26 AM, Dmitry Baryshkov wrote:
>>> On 03/05/2023 04:19, Jessica Zhang wrote:
>>>> Currently, word count is calculated using slice_count. This is incorrect
>>>> as downstream uses slice per packet, which is different from
>>>> slice_count.
>>>>
>>>> Slice count represents the number of soft slices per interface, and its
>>>> value will not always match that of slice per packet. For example, it is
>>>> possible to have cases where there are multiple soft slices per interface
>>>> but the panel specifies only one slice per packet.
>>>>
>>>> Thus, use the default value of one slice per packet and remove slice_count
>>>> from the word count calculation.
>>>>
>>>> Fixes: bc6b6ff8135c ("drm/msm/dsi: Use DSC slice(s) packet size to compute
>>>> word count")
>>>> Signed-off-by: Jessica Zhang <quic_jessz...@quicinc.com>
>>>> ---
>>>> drivers/gpu/drm/msm/dsi/dsi_host.c | 9 ++++++++-
>>>> 1 file changed, 8 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>> b/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>> index 35c69dbe5f6f..b0d448ffb078 100644
>>>> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>> @@ -996,7 +996,14 @@ static void dsi_timing_setup(struct msm_dsi_host
>>>> *msm_host, bool is_bonded_dsi)
>>>> if (!msm_host->dsc)
>>>> wc = hdisplay * dsi_get_bpp(msm_host->format) / 8 + 1;
>>>> else
>>>> - wc = msm_host->dsc->slice_chunk_size *
>>>> msm_host->dsc->slice_count + 1;
>>>> + /*
>>>> + * When DSC is enabled, WC = slice_chunk_size *
>>>> slice_per_packet + 1.
>>>> + * Currently, the driver only supports default value of
>>>> slice_per_packet = 1
>>>> + *
>>>> + * TODO: Expand drm_panel struct to hold slice_per_packet info
>>>> + * and adjust DSC math to account for slice_per_packet.
>>>
>>> slice_per_packet is not a part of the standard DSC, so I'm not sure how
>>> that can be implemented. And definitely we should not care about the
>>> drm_panel here. It should be either a part of drm_dsc_config, or
>>> mipi_dsi_device.
>>>
>>
>> This is not correct.
>>
>> It is part of the DSI standard (not DSC standard). Please refer to Figure 40
>> "One Line Containing One Packet with Data from One or More Compressed
>> Slices" and Figure 41 "One Line Containing More than One Compressed Pixel
>> Stream Packet".
>
> I have reviewed section 8.8.24 and Annex D of the DSI standard.
>
> It is not clear to me, if we can get away with always using slice_per_packet
> = 1. What is the DSI sink's difference between Fig. 40.(b) and Fig 41?
>
> Are there are known panels that require slice_per_packet != 1? If so, we will
> have to implement support for such configurations.
At least two different ones on expensive Xperias (souxp00_a+amb650wh07 and
sofef03_m)
Konrad
>
>> This has details about this. So I still stand by my point that this should
>> be in the drm_panel.
>
> Note, the driver doesn't use drm_panel directly. So slices_per_packet should
> go to mipi_dsi_device instead (which in turn can be filled from e.g.
> drm_panel or from any other source).
>
>>
>>>> + */
>>>> + wc = msm_host->dsc->slice_chunk_size + 1;
>>>> dsi_write(msm_host, REG_DSI_CMD_MDP_STREAM0_CTRL,
>>>> DSI_CMD_MDP_STREAM0_CTRL_WORD_COUNT(wc) |
>>>>
>>>
>
