Hi Stefan,
On Mi, 2019-08-14 at 13:03 +0200, Stefan Agner wrote:

On 2019-08-14 12:48, Robert Chiras wrote:

quoted

Add new optional property 'max-res', to limit the maximum supported
resolution by the MXSFB_DRM driver.

I would also mention the reason why we need this.

I guess this needs a vendor prefix as well (fsl,max-res). I also
would
like to have the ack of the device tree folks here.

Rob Herring also aked be about this, and I'll copy here the reply, with
explanations:

Indeed, this limitation is actually due to bandwidth limitation, but
the problem is that this limitation comes on i.MX8M (known as mScale
850D), where the memory bandwidth cannot support: GPU/VPU workload in
the same time with both DCSS driving 4k@60 and eLCDIF driving 1080p@60.
Since eLCDIF is a secondary display we though to add the posibility to
limit it's bandwidth by limiting the resolution.
If you say that more details are needed, I can add them in the
description.

--
Stefan

quoted

Signed-off-by: Robert Chiras <robert.chiras@nxp.com>
---
 Documentation/devicetree/bindings/display/mxsfb.txt | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/mxsfb.txt

b/Documentation/devicetree/bindings/display/mxsfb.txt
index 472e1ea..55e22ed 100644

--- a/Documentation/devicetree/bindings/display/mxsfb.txt
+++ b/Documentation/devicetree/bindings/display/mxsfb.txt

@@ -17,6 +17,12 @@ Required properties:

 Required sub-nodes:
   - port: The connection to an encoder chip.

+Optional properties:
+- max-res:   an array with a maximum of two integers, representing
the
+             maximum supported resolution, in the form of
+             <maxX>, <maxY>; if one of the item is <0>, the
default
+             driver-defined maximum resolution for that axis is
used
+
 Example:

      lcdif1: display-controller@2220000 {

Thanks,
Robert
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