Re: [Intel-gfx] [PATCH v3 2/2] drm/i915/dmc: Prepare to use unversioned paths

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Dec 29, 2022 at 04:07:40PM -0300, Gustavo Sousa wrote:
> New DMC releases in linux-firmware will stop using version number in
> blob filenames. This new convention provides the following benefits:
> 
>   1. It simplifies code maintenance, as new DMC releases for a platform
>      using the new convention will always use the same filename for the
>      blob.
> 
>   2. It allows DMC to be loaded even if the target system does not have
>      the most recent firmware installed.
> 
> Prepare the driver by:
> 
>   - Using the new convention for DMC_PATH() and renaming the currently
>     used one to make it clear it is for the legacy scheme.
> 
>   - Implementing a fallback mechanism for future transitions from
>     versioned to unversioned paths so that we do not cause a regression
>     for systems not having the most up-to-date linux-firmware files.
> 
> v2:
>   - Keep using request_firmware() instead of firmware_request_nowarn().
>     (Jani)
> v3:
>   - Keep current DMC paths instead of directly using unversioned ones,
>     so that we do not disturb initrd generation.
>     (Lucas, Rodrigo)
> 
> References: https://lore.kernel.org/r/Y3081s7c5ksutpMW@intel.com

I also don't believe this link is a good reference here...

Regarding the patch, I liked the approach in general.

The patch is really neat, but I believe we will need to split it:

1. Add the new DMC_PATH and DMC_LEGACY_PATH only with the introduction
of the mtl_dmc.bin

2. And the fallback function, add only if/when we get a real fallback.

Oh, and I just realized that when doing the new _dmc.bin path we also
need to make sure that we read the fw_version from the header and
print as a drm_info msg somewhere.

> Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dmc.c | 62 ++++++++++++++++++------
>  1 file changed, 46 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dmc.c b/drivers/gpu/drm/i915/display/intel_dmc.c
> index 4124b3d37110..12f05b2d33a3 100644
> --- a/drivers/gpu/drm/i915/display/intel_dmc.c
> +++ b/drivers/gpu/drm/i915/display/intel_dmc.c
> @@ -42,51 +42,59 @@
>  #define DMC_VERSION_MAJOR(version)	((version) >> 16)
>  #define DMC_VERSION_MINOR(version)	((version) & 0xffff)
>  
> -#define DMC_PATH(platform, major, minor) \
> -	"i915/"				 \
> -	__stringify(platform) "_dmc_ver" \
> -	__stringify(major) "_"		 \
> +#define DMC_PATH(platform) \
> +	"i915/" __stringify(platform) "_dmc.bin"
> +
> +/*
> + * 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.
> + */
> +#define DMC_LEGACY_PATH(platform, major, minor) \
> +	"i915/"					\
> +	__stringify(platform) "_dmc_ver"	\
> +	__stringify(major) "_"			\
>  	__stringify(minor) ".bin"
>  
>  #define DISPLAY_VER13_DMC_MAX_FW_SIZE	0x20000
>  
>  #define DISPLAY_VER12_DMC_MAX_FW_SIZE	ICL_DMC_MAX_FW_SIZE
>  
> -#define DG2_DMC_PATH			DMC_PATH(dg2, 2, 08)
> +#define DG2_DMC_PATH			DMC_LEGACY_PATH(dg2, 2, 08)
>  MODULE_FIRMWARE(DG2_DMC_PATH);
>  
> -#define ADLP_DMC_PATH			DMC_PATH(adlp, 2, 16)
> +#define ADLP_DMC_PATH			DMC_LEGACY_PATH(adlp, 2, 16)
>  MODULE_FIRMWARE(ADLP_DMC_PATH);
>  
> -#define ADLS_DMC_PATH			DMC_PATH(adls, 2, 01)
> +#define ADLS_DMC_PATH			DMC_LEGACY_PATH(adls, 2, 01)
>  MODULE_FIRMWARE(ADLS_DMC_PATH);
>  
> -#define DG1_DMC_PATH			DMC_PATH(dg1, 2, 02)
> +#define DG1_DMC_PATH			DMC_LEGACY_PATH(dg1, 2, 02)
>  MODULE_FIRMWARE(DG1_DMC_PATH);
>  
> -#define RKL_DMC_PATH			DMC_PATH(rkl, 2, 03)
> +#define RKL_DMC_PATH			DMC_LEGACY_PATH(rkl, 2, 03)
>  MODULE_FIRMWARE(RKL_DMC_PATH);
>  
> -#define TGL_DMC_PATH			DMC_PATH(tgl, 2, 12)
> +#define TGL_DMC_PATH			DMC_LEGACY_PATH(tgl, 2, 12)
>  MODULE_FIRMWARE(TGL_DMC_PATH);
>  
> -#define ICL_DMC_PATH			DMC_PATH(icl, 1, 09)
> +#define ICL_DMC_PATH			DMC_LEGACY_PATH(icl, 1, 09)
>  #define ICL_DMC_MAX_FW_SIZE		0x6000
>  MODULE_FIRMWARE(ICL_DMC_PATH);
>  
> -#define GLK_DMC_PATH			DMC_PATH(glk, 1, 04)
> +#define GLK_DMC_PATH			DMC_LEGACY_PATH(glk, 1, 04)
>  #define GLK_DMC_MAX_FW_SIZE		0x4000
>  MODULE_FIRMWARE(GLK_DMC_PATH);
>  
> -#define KBL_DMC_PATH			DMC_PATH(kbl, 1, 04)
> +#define KBL_DMC_PATH			DMC_LEGACY_PATH(kbl, 1, 04)
>  #define KBL_DMC_MAX_FW_SIZE		BXT_DMC_MAX_FW_SIZE
>  MODULE_FIRMWARE(KBL_DMC_PATH);
>  
> -#define SKL_DMC_PATH			DMC_PATH(skl, 1, 27)
> +#define SKL_DMC_PATH			DMC_LEGACY_PATH(skl, 1, 27)
>  #define SKL_DMC_MAX_FW_SIZE		BXT_DMC_MAX_FW_SIZE
>  MODULE_FIRMWARE(SKL_DMC_PATH);
>  
> -#define BXT_DMC_PATH			DMC_PATH(bxt, 1, 07)
> +#define BXT_DMC_PATH			DMC_LEGACY_PATH(bxt, 1, 07)
>  #define BXT_DMC_MAX_FW_SIZE		0x3000
>  MODULE_FIRMWARE(BXT_DMC_PATH);
>  
> @@ -821,16 +829,38 @@ static void intel_dmc_runtime_pm_put(struct drm_i915_private *dev_priv)
>  	intel_display_power_put(dev_priv, POWER_DOMAIN_INIT, wakeref);
>  }
>  
> +static const char *dmc_fallback_path(struct drm_i915_private *i915)
> +{
> +	/* No fallback paths for now. */
> +	return NULL;
> +}
> +
>  static void dmc_load_work_fn(struct work_struct *work)
>  {
>  	struct drm_i915_private *dev_priv;
>  	struct intel_dmc *dmc;
>  	const struct firmware *fw = NULL;
> +	const char *fallback_path;
> +	int err;
>  
>  	dev_priv = container_of(work, typeof(*dev_priv), display.dmc.work);
>  	dmc = &dev_priv->display.dmc;
>  
> -	request_firmware(&fw, dev_priv->display.dmc.fw_path, dev_priv->drm.dev);
> +	err = request_firmware(&fw, dev_priv->display.dmc.fw_path, dev_priv->drm.dev);
> +
> +	if (err == -ENOENT && !dev_priv->params.dmc_firmware_path) {
> +		fallback_path = dmc_fallback_path(dev_priv);
> +		if (fallback_path) {
> +			drm_dbg_kms(&dev_priv->drm,
> +				    "%s not found, falling back to %s\n",
> +				    dmc->fw_path,
> +				    fallback_path);
> +			err = request_firmware(&fw, fallback_path, dev_priv->drm.dev);
> +			if (err == 0)
> +				dev_priv->display.dmc.fw_path = fallback_path;
> +		}
> +	}
> +
>  	parse_dmc_fw(dev_priv, fw);
>  
>  	if (intel_dmc_has_payload(dev_priv)) {
> -- 
> 2.39.0
>