Re: [PATCH] drm: mediatek: mtk_dsi: Fix NO_EOT_PACKET settings/handling

[Alexandre Mergnat <amergnat@baylibre.com>]

On 23/06/2023 11:47, AngeloGioacchino Del Regno wrote:
> Il 23/05/23 12:42, AngeloGioacchino Del Regno ha scritto:
>> Due to the initial confusion about MIPI_DSI_MODE_EOT_PACKET, properly
>> renamed to MIPI_DSI_MODE_NO_EOT_PACKET, reflecting its actual meaning,
>> both the DSI_TXRX_CON register setting for bit (HSTX_)DIS_EOT and the
>> later calculation for horizontal sync-active (HSA), back (HBP) and
>> front (HFP) porches got incorrect due to the logic being inverted.
>>
>> This means that a number of settings were wrong because....:
>>   - DSI_TXRX_CON register setting: bit (HSTX_)DIS_EOT should be
>>     set in order to disable the End of Transmission packet;
>>   - Horizontal Sync and Back/Front porches: The delta used to
>>     calculate all of HSA, HBP and HFP should account for the
>>     additional EOT packet.
>>
>> Before this change...
>>   - Bit (HSTX_)DIS_EOT was being set when EOT packet was enabled;
>>   - For HSA/HBP/HFP delta... all three were wrong, as words were
>>     added when EOT disabled, instead of when EOT packet enabled!
>>
>> Invert the logic around flag MIPI_DSI_MODE_NO_EOT_PACKET in the
>> MediaTek DSI driver to fix the aforementioned issues.
>>
>> Fixes: 8b2b99fd7931 ("drm/mediatek: dsi: Fine tune the line time 
>> caused by EOTp")
>> Fixes: 2d52bfba09d1 ("drm/mediatek: add non-continuous clock mode and 
>> EOT packet control")
>> Signed-off-by: AngeloGioacchino Del Regno 
>> <angelogioacchino.delregno@collabora.com>
> 
> Gentle ping for an important fix.
> 
> Regards,
> Angelo
> 
>> ---
>>   drivers/gpu/drm/mediatek/mtk_dsi.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c 
>> b/drivers/gpu/drm/mediatek/mtk_dsi.c
>> index 7d5250351193..b0ab38e59db9 100644
>> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
>> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
>> @@ -407,7 +407,7 @@ static void mtk_dsi_rxtx_control(struct mtk_dsi *dsi)
>>       if (dsi->mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS)
>>           tmp_reg |= HSTX_CKLP_EN;
>> -    if (!(dsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET))
>> +    if (dsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
>>           tmp_reg |= DIS_EOT;
>>       writel(tmp_reg, dsi->regs + DSI_TXRX_CTRL);
>> @@ -484,7 +484,7 @@ static void mtk_dsi_config_vdo_timing(struct 
>> mtk_dsi *dsi)
>>                 timing->da_hs_zero + timing->da_hs_exit + 3;
>>       delta = dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST ? 18 : 12;
>> -    delta += dsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET ? 2 : 0;
>> +    delta += dsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET ? 0 : 2;
>>       horizontal_frontporch_byte = vm->hfront_porch * dsi_tmp_buf_bpp;
>>       horizontal_front_back_byte = horizontal_frontporch_byte + 
>> horizontal_backporch_byte;
> 
> 

Sounds logic

Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>

-- 
Regards,
Alexandre