Re: [PATCH 08/10] drm/tidss: oldi: Fix OLDI signal polarities

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Modifying driver-private state in atomic check callback violates atomic modesetting semantics.
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commit 3406ad4360f9e6a4eda4b2203c1f6400e5e7ab77
Author: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

drm/tidss: oldi: Fix OLDI signal polarities

This commit fixes OLDI signal polarities by removing drm_bridge_timings
and properly setting input_bus_cfg.flags in tidss_oldi_atomic_check(),
as well as setting OLDI_DEPOL based on the DE bus flag.

> diff --git a/drivers/gpu/drm/tidss/tidss_oldi.c b/drivers/gpu/drm/tidss/tidss_oldi.c
> index 5eb749f495d59..624f1646fb07a 100644
> --- a/drivers/gpu/drm/tidss/tidss_oldi.c
> +++ b/drivers/gpu/drm/tidss/tidss_oldi.c

[ ... ]

> @@ -329,7 +352,8 @@ tidss_oldi_mode_valid(struct drm_bridge *bridge,
>  }
>  
>  static const struct drm_bridge_funcs tidss_oldi_bridge_funcs = {
> -	.attach	= tidss_oldi_bridge_attach,
> +	.attach = tidss_oldi_bridge_attach,
> +	.atomic_check = tidss_oldi_atomic_check,
>  	.atomic_pre_enable = tidss_oldi_atomic_pre_enable,
>  	.atomic_post_disable = tidss_oldi_atomic_post_disable,
>  	.atomic_get_input_bus_fmts = tidss_oldi_atomic_get_input_bus_fmts,

[Severity: High]
This isn't a bug introduced by this patch, but does the implementation of
tidss_oldi_atomic_get_input_bus_fmts() violate atomic modesetting
semantics by modifying driver-private state during the check phase?

In drivers/gpu/drm/tidss/tidss_oldi.c:tidss_oldi_atomic_get_input_bus_fmts():

        input_fmts[0] = oldi_bus_formats[i].input_bus_fmt;
        oldi->bus_format = &oldi_bus_formats[i];

A TEST_ONLY atomic commit or concurrent commits can alter the global
driver-private state (oldi->bus_format). This could cause a subsequent
real commit to program the hardware with an incorrect bus format, leading
to display corruption.

Should this configuration decision be stored in the drm_bridge_state object
instead of the driver-private tidss_oldi structure?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260903-tidss-pre-beagley-v1-0-93928baa8b12@ideasonboard.com?part=8