Messages in this thread | | | Date | Mon, 22 Apr 2024 21:43:13 +0200 | Subject | Re: [PATCH V2 2/2] drm/bridge: samsung-dsim: Fix porch calcalcuation rounding | From | Marek Vasut <> |
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On 4/22/24 3:04 PM, Adam Ford wrote: > On Mon, Apr 22, 2024 at 8:01 AM Marek Vasut <marex@denx.de> wrote: >> >> On 4/22/24 2:09 PM, Adam Ford wrote: >>> On Sun, Apr 21, 2024 at 9:36 AM Marek Vasut <marex@denx.de> wrote: >>>> >>>> On 2/12/24 12:09 AM, Adam Ford wrote: >>>>> When using video sync pulses, the HFP, HBP, and HSA are divided between >>>>> the available lanes if there is more than one lane. For certain >>>>> timings and lane configurations, the HFP may not be evenly divisible. >>>>> If the HFP is rounded down, it ends up being too small which can cause >>>>> some monitors to not sync properly. In these instances, adjust htotal >>>>> and hsync to round the HFP up, and recalculate the htotal. >>>>> >>>>> Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de> # Kontron BL i.MX8MM with HDMI monitor >>>>> Signed-off-by: Adam Ford <aford173@gmail.com> >>>>> --- >>>>> V2: No changes >>>>> >>>>> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c >>>>> index 8476650c477c..52939211fe93 100644 >>>>> --- a/drivers/gpu/drm/bridge/samsung-dsim.c >>>>> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c >>>>> @@ -1606,6 +1606,27 @@ static int samsung_dsim_atomic_check(struct drm_bridge *bridge, >>>>> adjusted_mode->flags |= (DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC); >>>>> } >>>>> >>>>> + /* >>>>> + * When using video sync pulses, the HFP, HBP, and HSA are divided between >>>>> + * the available lanes if there is more than one lane. For certain >>>>> + * timings and lane configurations, the HFP may not be evenly divisible. >>>>> + * If the HFP is rounded down, it ends up being too small which can cause >>>>> + * some monitors to not sync properly. In these instances, adjust htotal >>>>> + * and hsync to round the HFP up, and recalculate the htotal. Through trial >>>>> + * and error, it appears that the HBP and HSA do not appearto need the same >>>>> + * correction that HFP does. >>>>> + */ >>>>> + if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE && dsi->lanes > 1) { >>>> >>>> Does this also apply to mode with sync events (I suspect it does), so >>>> the condition here should likely be if (!...burst mode) , right ? >>> >>> Thanks for the review! >>> >>> I was only able to test it with the DSI->ADV6535 bridge, and I'll >>> admit I don't know a lot about DSI interface since I don't have a copy >>> of the spec to read. >>> >>> Are you proposing this should be: >>> >>> if (!(dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST) && dsi->lanes > 1) { >>> >>> I just want to make sure I understand what you're requesting. >> >> Yes, exactly this. > > Do you think it should also include checks for > MIPI_DSI_MODE_VIDEO_NO_HFP, MIPI_DSI_MODE_VIDEO_NO_HBP or > MIPI_DSI_MODE_VIDEO_NO_HSA? > > It seems like if any of these are set, we should skip this rounding stuff.
Now that you ask this question, shouldn't this actually apply unconditionally , no matter which mode is in use ?
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