Re: [PATCH v2 4/6] drm/msm/dsi: add a comment to explain pkt_per_line encoding

Jonathan Marek
2023-11-16T18:46:50Z

On 11/15/23 2:38 AM, Dmitry Baryshkov wrote:
> On Wed, 15 Nov 2023 at 01:00, Jonathan Marek <jonathan@marek.ca> wrote:
>>
>> Make it clear why the pkt_per_line value is being "divided by 2".
>>
>> Signed-off-by: Jonathan Marek <jonathan@marek.ca>
>> ---
>> drivers/gpu/drm/msm/dsi/dsi_host.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
>> index 66f198e21a7e..842765063b1b 100644
>> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
>> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
>> @@ -877,6 +877,8 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
>> /* DSI_VIDEO_COMPRESSION_MODE & DSI_COMMAND_COMPRESSION_MODE
>> * registers have similar offsets, so for below common code use
>> * DSI_VIDEO_COMPRESSION_MODE_XXXX for setting bits
>> + *
>> + * pkt_per_line is log2 encoded, >>1 works for supported values (1,2,4)
>> */
>> reg |= DSI_VIDEO_COMPRESSION_MODE_CTRL_PKT_PER_LINE(pkt_per_line >> 1);
>
> Should we switch to ffs() or fls() instead?
>

Just a ffs() on its own can be confusing as well (without the
information that only powers of two are possible), I think like this is
better.

>> reg |= DSI_VIDEO_COMPRESSION_MODE_CTRL_EOL_BYTE_NUM(eol_byte_num);
>> --
>> 2.26.1
>>
>
>