linux-kernel - Re: [PATCH] drm: mediatek: mtk_dsi: Fix NO_EOT

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Message-ID: <735623c5-3eeb-bda3-db87-2b33d9ad3446@collabora.com>
Date:   Fri, 23 Jun 2023 11:47:49 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     chunkuang.hu@...nel.org
Cc:     p.zabel@...gutronix.de, airlied@...il.com, daniel@...ll.ch,
        matthias.bgg@...il.com, jitao.shi@...iatek.com, ck.hu@...iatek.com,
        shaoming.chen@...iatek.com, yt.shen@...iatek.com,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] drm: mediatek: mtk_dsi: Fix NO_EOT_PACKET
 settings/handling

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@...labora.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;