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

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Date:   Fri, 15 Sep 2023 12:11:24 +0200
From:   Michael Walle <mwalle@...nel.org>
To:     angelogioacchino.delregno@...labora.com
Cc:     airlied@...il.com, chunkuang.hu@...nel.org, ck.hu@...iatek.com,
        daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        jitao.shi@...iatek.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        matthias.bgg@...il.com, p.zabel@...gutronix.de,
        shaoming.chen@...iatek.com, yt.shen@...iatek.com,
        Michael Walle <mwalle@...nel.org>
Subject: Re: [PATCH] drm: mediatek: mtk_dsi: Fix NO_EOT_PACKET settings/handling

> 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>

Tested-by: Michael Walle <mwalle@...nel.org>

Thanks,
-michael