Re: [PATCH 2/3] arm64: dts: ti: k3-j721e-main.dtsi: Add DSS node
From: Tero Kristo
Date: Mon Apr 27 2020 - 07:41:54 EST
On 27/04/2020 14:37, Tomi Valkeinen wrote:
On 27/04/2020 14:15, Tomi Valkeinen wrote:
On 27/04/2020 14:10, Jyri Sarha wrote:
On 27/04/2020 13:51, Tomi Valkeinen wrote:
On 27/04/2020 13:37, Jyri Sarha wrote:
On 27/04/2020 13:09, Tero Kristo wrote:
+ÂÂÂÂÂÂÂ status = "disabled";
Again, why disabled by default?
tidss device is not functional without a defined video-port. The
driver
is not implemented in a way that it would handle a broken
configuration
gracefully.
Then we need to fix it. The driver should handle the case where there
are no ports defined just fine.
Just by reading the code, I would say that currently the probe would
fail with returned -ENOMEM after calling drm_vblank_init() with zero
CRTCs.
So should the probe fail gracefully and silently, or should we try to
register a DRM device with no CRTCs? Is that even possible?
My first thought is that the driver should exit probe silently with
ENODEV if there are no outputs defined (but, of course, with
EPROBE_DEFER if there are outputs which haven't been probed yet).
It gets a bit more complex if we ever support writeback, as that can
be used as mem-to-mem without any displays, but I think we can ignore
that for now.
In any case, that's not the reason for status = "disabled", so that
discussion is not related to these patches as such.
The reason to have DSS disabled is just to prevent pointless driver
probing. When a board dts or a DT overlay adds a display, the DSS DT
node has to be modified anyway to add the DT graph and the panel/bridge
data. So one can as well add the single line of "status = enabled" there.
Ok, thanks for the explanation, queued all three patches towards 5.8
based on that.
-Tero
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