drm/i915/csr: keep max firmware size together with firmare name and version

Move max firmware size to the same if ladder with firmware name and
required version. This allows us to detect the missing max size for a
platform without actually loading the firmware, and makes the whole
thing easier to maintain.

We need to move the power get earlier to allow for early return in the
missing platform case. While at it, extend the comment on why we return
with the reference held on errors.

We also need to move the module parameter override later to reuse the
max firmware size, which is independent of the override.

v2: Add comment on why we leak the wakeref on errors (Chris)

v3: Rebase
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180926133414.22073-2-jani.nikula@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -466,8 +466,9 @@ struct intel_csr {
 	struct work_struct work;
 	const char *fw_path;
 	uint32_t required_version;
+	uint32_t max_fw_size; /* bytes */
 	uint32_t *dmc_payload;
-	uint32_t dmc_fw_size;
+	uint32_t dmc_fw_size; /* dwords */
 	uint32_t version;
 	uint32_t mmio_count;
 	i915_reg_t mmioaddr[8];

drivers/gpu/drm/i915/intel_csr.c

@@ -284,7 +284,6 @@ static uint32_t *parse_csr_fw(struct drm_i915_private *dev_priv,
 	struct intel_csr *csr = &dev_priv->csr;
 	const struct stepping_info *si = intel_get_stepping_info(dev_priv);
 	uint32_t dmc_offset = CSR_DEFAULT_FW_OFFSET, readcount = 0, nbytes;
-	uint32_t max_fw_size = 0;
 	uint32_t i;
 	uint32_t *dmc_payload;
 
@@ -381,15 +380,7 @@ static uint32_t *parse_csr_fw(struct drm_i915_private *dev_priv,
 
 	/* fw_size is in dwords, so multiplied by 4 to convert into bytes. */
 	nbytes = dmc_header->fw_size * 4;
-	if (INTEL_GEN(dev_priv) >= 11)
-		max_fw_size = ICL_CSR_MAX_FW_SIZE;
-	else if (IS_CANNONLAKE(dev_priv) || IS_GEMINILAKE(dev_priv))
-		max_fw_size = GLK_CSR_MAX_FW_SIZE;
-	else if (IS_GEN9(dev_priv))
-		max_fw_size = BXT_CSR_MAX_FW_SIZE;
-	else
-		MISSING_CASE(INTEL_REVID(dev_priv));
-	if (nbytes > max_fw_size) {
+	if (nbytes > csr->max_fw_size) {
 		DRM_ERROR("DMC FW too big (%u bytes)\n", nbytes);
 		return NULL;
 	}
@@ -454,35 +445,50 @@ void intel_csr_ucode_init(struct drm_i915_private *dev_priv)
 	if (!HAS_CSR(dev_priv))
 		return;
 
-	if (i915_modparams.dmc_firmware_path) {
-		csr->fw_path = i915_modparams.dmc_firmware_path;
-		/* Bypass version check for firmware override. */
-		csr->required_version = 0;
-	} else if (IS_ICELAKE(dev_priv)) {
+	/*
+	 * Obtain a runtime pm reference, until CSR is loaded, to avoid entering
+	 * runtime-suspend.
+	 *
+	 * On error, we return with the rpm wakeref held to prevent runtime
+	 * suspend as runtime suspend *requires* a working CSR for whatever
+	 * reason.
+	 */
+	intel_display_power_get(dev_priv, POWER_DOMAIN_INIT);
+
+	if (IS_ICELAKE(dev_priv)) {
 		csr->fw_path = I915_CSR_ICL;
 		csr->required_version = ICL_CSR_VERSION_REQUIRED;
+		csr->max_fw_size = ICL_CSR_MAX_FW_SIZE;
 	} else if (IS_CANNONLAKE(dev_priv)) {
 		csr->fw_path = I915_CSR_CNL;
 		csr->required_version = CNL_CSR_VERSION_REQUIRED;
+		csr->max_fw_size = GLK_CSR_MAX_FW_SIZE;
 	} else if (IS_GEMINILAKE(dev_priv)) {
 		csr->fw_path = I915_CSR_GLK;
 		csr->required_version = GLK_CSR_VERSION_REQUIRED;
+		csr->max_fw_size = GLK_CSR_MAX_FW_SIZE;
 	} else if (IS_KABYLAKE(dev_priv) || IS_COFFEELAKE(dev_priv)) {
 		csr->fw_path = I915_CSR_KBL;
 		csr->required_version = KBL_CSR_VERSION_REQUIRED;
+		csr->max_fw_size = BXT_CSR_MAX_FW_SIZE;
 	} else if (IS_SKYLAKE(dev_priv)) {
 		csr->fw_path = I915_CSR_SKL;
 		csr->required_version = SKL_CSR_VERSION_REQUIRED;
+		csr->max_fw_size = BXT_CSR_MAX_FW_SIZE;
 	} else if (IS_BROXTON(dev_priv)) {
 		csr->fw_path = I915_CSR_BXT;
 		csr->required_version = BXT_CSR_VERSION_REQUIRED;
+		csr->max_fw_size = BXT_CSR_MAX_FW_SIZE;
+	} else {
+		MISSING_CASE(INTEL_REVID(dev_priv));
+		return;
 	}
 
-	/*
-	 * Obtain a runtime pm reference, until CSR is loaded,
-	 * to avoid entering runtime-suspend.
-	 */
-	intel_display_power_get(dev_priv, POWER_DOMAIN_INIT);
+	if (i915_modparams.dmc_firmware_path) {
+		csr->fw_path = i915_modparams.dmc_firmware_path;
+		/* Bypass version check for firmware override. */
+		csr->required_version = 0;
+	}
 
 	if (csr->fw_path == NULL) {
 		DRM_DEBUG_KMS("No known CSR firmware for platform, disabling runtime PM\n");