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SubjectRe: [PATCH v4 5/5] drm/msm/dsi: Remove incorrect references to slice_count
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On 5/22/2023 2:01 PM, Marijn Suijten wrote:
> On 2023-05-22 13:30:24, Jessica Zhang wrote:
>> Currently, slice_count is being used to calculate word count and
>> pkt_per_line. Instead, these values should be calculated using slice per
>> packet, which is not the same as 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.
>
> As discussed in many patches before, there is no definition of "soft
> slices" anyhwere. Unless we can have that, and reference it, this
> should more clearly explain what it means or leave out the word "soft"
> altogether.

Hi Marijn,

Acked.

>
>> Thus, use the default value of one slice per packet and remove slice_count
>> from the aforementioned calculations.
>>
>> Fixes: 08802f515c3c ("drm/msm/dsi: Add support for DSC configuration")
>> Fixes: bc6b6ff8135c ("drm/msm/dsi: Use DSC slice(s) packet size to compute word count")
>> Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
>> ---
>> drivers/gpu/drm/msm/dsi/dsi_host.c | 26 ++++++++++++++++----------
>> 1 file changed, 16 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
>> index d04f8bbd707d..2eed99afdba9 100644
>> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
>> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
>> @@ -866,18 +866,17 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
>> */
>> slice_per_intf = msm_dsc_get_slices_per_intf(dsc, hdisplay);
>>
>> - /*
>> - * If slice_count is greater than slice_per_intf
>> - * then default to 1. This can happen during partial
>> - * update.
>> - */
>> - 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 = total_bytes_per_intf % 3;
>> - pkt_per_line = slice_per_intf / dsc->slice_count;
>> +
>> + /*
>> + * Typically, pkt_per_line = slice_per_intf * slice_per_pkt.
>> + *
>> + * Since the current driver only supports slice_per_pkt = 1,
>> + * pkt_per_line will be equal to slice per intf for now.
>> + */
>> + pkt_per_line = slice_per_intf;
>>
>> if (is_cmd_mode) /* packet data type */
>> reg = DSI_COMMAND_COMPRESSION_MODE_CTRL_STREAM0_DATATYPE(MIPI_DSI_DCS_LONG_WRITE);
>> @@ -1001,7 +1000,14 @@ 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 mipi_dsi_device struct to hold slice_per_packet info
>> + * and adjust DSC math to account for slice_per_packet.
>> + */
>
> Either rename this all to slice_per_pkt, or rename the above comment to
> slice_per_packet.

Acked.

Thanks,

Jessica Zhang

>
> After improving on that:
>
> Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
>
> We all learned the wrong thing initially, thanks for clearing up that
> slice_count != slice_per_pkt.
>
> - Marijn
>
>> + 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) |
>>
>> --
>> 2.40.1
>>

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