Messages in this thread | | | Date | Mon, 22 Apr 2024 14:30:59 +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 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.
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