Re: [PATCH] [CI] drm/i915/dmc: Test Xe3p_LPD DMC v2.44

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] drm/i915/dmc: hardcoded CI-only firmware path in XE3P_LPD_DMC_PATH
--

commit 6720c799eff7439b665b842fb4acf1ad6594772f
Author: Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com>

drm/i915/dmc: Test Xe3p_LPD DMC v2.44

This commit replaces the unversioned DMC_PATH(xe3p_lpd) macro in
XE3P_LPD_DMC_PATH with a hardcoded versioned firmware path for CI testing.

> diff --git a/drivers/gpu/drm/i915/display/intel_dmc.c b/drivers/gpu/drm/i915/display/intel_dmc.c
> index 56e831b2a8262..864b419098ac0 100644
> --- a/drivers/gpu/drm/i915/display/intel_dmc.c
> +++ b/drivers/gpu/drm/i915/display/intel_dmc.c
> @@ -126,7 +126,7 @@ static bool dmc_firmware_param_disabled(struct intel_display *display)
>  #define DISPLAY_VER13_DMC_MAX_FW_SIZE	0x20000
>  #define DISPLAY_VER12_DMC_MAX_FW_SIZE	ICL_DMC_MAX_FW_SIZE
>  
> -#define XE3P_LPD_DMC_PATH		DMC_PATH(xe3p_lpd)
> +#define XE3P_LPD_DMC_PATH		"i915/xe3p_lpd_dmc_ver2_44.bin"

[Severity: High]
As noted in the commit message, this is a temporary CI test patch and is not
intended to be merged.

All platforms from MTL onward use unversioned DMC firmware paths via
DMC_PATH(), as documented above DMC_LEGACY_PATH in
drivers/gpu/drm/i915/display/intel_dmc.c:

/*
 * New DMC additions should not use this. This is used solely to remain
 * compatible with systems that have not yet updated DMC blobs to use
 * unversioned file names.
 */

During driver probe on Xe3p_LPD (DISPLAY_VERx100(display) == 3500),
intel_dmc_init() acquires the POWER_DOMAIN_INIT runtime PM reference via
intel_dmc_runtime_pm_get(), sets dmc->fw_path to XE3P_LPD_DMC_PATH via
dmc_firmware_default(), and schedules dmc_load_work_fn().

Because dmc_fallback_path() only provides a fallback for Alder Lake-P and
returns NULL on Xe3p_LPD, replacing DMC_PATH(xe3p_lpd) with
"i915/xe3p_lpd_dmc_ver2_44.bin" causes request_firmware() in
dmc_load_work_fn() to fail with -ENOENT on systems shipping the standard
unversioned "i915/xe3p_lpd_dmc.bin" linux-firmware blob:

drivers/gpu/drm/i915/display/intel_dmc.c:dmc_load_work_fn() {
	...
	if (err) {
		drm_notice(display->drm,
			   "Failed to load DMC firmware %s (%pe). Disabling runtime power management.\n",
			   dmc->fw_path, ERR_PTR(err));
		drm_notice(display->drm, "DMC firmware homepage: %s",
			   INTEL_DMC_FIRMWARE_URL);
		return;
	}
	...
}

When this happens, dmc_load_work_fn() returns early without calling
intel_dmc_runtime_pm_put(), leaving the DMC unprogrammed and permanently
disabling display runtime power management. It also changes
MODULE_FIRMWARE(XE3P_LPD_DMC_PATH) so initramfs generators look for the
versioned filename instead of "i915/xe3p_lpd_dmc.bin".

Could CI pass the versioned firmware path via the dmc_firmware_path module
parameter (read by dmc_firmware_param()) instead of modifying
XE3P_LPD_DMC_PATH?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261105091559.1784255-1-dibin.moolakadan.subrahmanian@intel.com?part=1