Re: [PATCH v5 09/10] drm/msm/dpu: only reassign resources when the encoder is reprogrammed

[Joonhoe Kim <26rote@gmail.com>]

On 10/26/26 10:19 AM, Konrad Dybcio wrote:
> LLM is curious whether turning off CTM/GAMMA should trigger a modeset too.
> My hunch is "yes"

Some data for that. I tested 7/10 and this patch on v7.3, on a Lenovo
Y700 Gen 5 (TB323FU, Kaanapali, bonded DSI) with out-of-tree board
support. I counted msm_dsi_host_power_off/on with kprobes.

- A compositor faded a night light filter in and out twice through
  the legacy CTM property. These are blob -> blob updates only. No
  modesets, no visible blink.

- With no compositor running, a small client set the CTM through the
  legacy property ioctl: two rounds of NULL -> A -> B -> A -> NULL.
  No modesets. The CRTC kept its DSPPs after each A -> NULL.

So turning the CTM off does not release the DSPPs. On chips with a
single DSPP, another CRTC asking for a CTM would then fail
dpu_rm_reserve(), as I noted on v4. This run does not cover the first
NULL -> blob on a CRTC without DSPPs.

As with v4, the tree carries out-of-tree SPR (sub-pixel rendering)
support. For the test, dpu_crtc_needs_dspp() also returned true when
SPR is enabled.

Tested-by: Joonhoe Kim <26rote@gmail.com> # Kaanapali

Thanks,
Joonhoe Kim