Re: [PATCH v3 2/2] drm/panel: add Ilitek ILI7807S panel driver

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] Incorrect and non-atomic modification of `dsi->mode_flags` permanently enables Low Power Mode and introduces a data race.
- [High] Backlight `update_status` sends DSI commands without verifying that the panel is powered on, risking DSI host timeouts.
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commit 2f966f15c21adb82ce5699cdffad22cac6628b98
Author: Arpit Saini <arpit.saini@oss.qualcomm.com>

drm/panel: add Ilitek ILI7807S panel driver
    
Add a DRM panel driver for the DLC DLC0697 1080x1920@60Hz MIPI DSI
panel based on the Ilitek ILI7807S display controller.

> diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili7807s.c b/drivers/gpu/drm/panel/panel-ilitek-ili7807s.c
> new file mode 100644
> index 0000000000000..8ddfab2693ec8
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-ilitek-ili7807s.c

[ ... ]

> +static int ili7807s_bl_update_status(struct backlight_device *bl)
> +{
> +	struct mipi_dsi_device *dsi = bl_get_data(bl);
> +	u16 brightness = backlight_get_brightness(bl);
> +	int ret;
> +

[Severity: High]
Does this code send DSI commands without verifying if the panel is powered on?

If the panel regulators are disabled and reset is asserted via
ili7807s_unprepare(), attempting to communicate with it here during a sysfs
backlight update could result in DSI host bus timeouts or hardware lockups.

Should there be a check against a power state tracking flag before
sending the DCS command?

> +	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
> +
> +	ret = mipi_dsi_dcs_set_display_brightness_large(dsi, brightness);
> +
> +	dsi->mode_flags |= MIPI_DSI_MODE_LPM;

[Severity: High]
Does unconditionally setting MIPI_DSI_MODE_LPM here permanently alter the
panel's base operating state?

Since the mode_flags are modified without synchronization with DRM modeset
paths (like ili7807s_on() and ili7807s_off()), could this create a data
race?

Also, the logic clears the flag before the transaction and unconditionally
sets it afterwards, leaving Low Power Mode permanently enabled for
subsequent DSI transmissions.

> +
> +	return ret;
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260624-ili7807s-v3-0-ddf37052a289@oss.qualcomm.com?part=2