drm/i915/dmc: extract fw_info and table walk from intel_package_header

Move fw_info out of struct intel_package_header to allow it to grow more
easily in future. To make a cleaner move, let's also extract a function to
search the header for the dmc_offset.

While reviewing this code I wondered why we continued the search even
after finding a suitable firmware. Add a comment to explain we will
continue to try to find a more specific firmware version, even if this
is not required by the spec.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190607091230.1489-3-lucas.demarchi@intel.com

diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
index 307ca793630d66fc57e6ca7d9e81002dc0e2e994..3c1642e47973eb44696ce20c5f03d9490c853f3d 100644 (file)
--- a/drivers/gpu/drm/i915/intel_csr.c
+++ b/drivers/gpu/drm/i915/intel_csr.c
@@ -70,6 +70,7 @@ MODULE_FIRMWARE(SKL_CSR_PATH);
 MODULE_FIRMWARE(BXT_CSR_PATH);
 
 #define CSR_DEFAULT_FW_OFFSET          0xFFFFFFFF
+#define PACKAGE_MAX_FW_INFO_ENTRIES    20
 
 struct intel_css_header {
        /* 0x09 for DMC */
@@ -139,8 +140,6 @@ struct intel_package_header {
 
        /* Number of valid entries in the FWInfo array below */
        u32 num_entries;
-
-       struct intel_fw_info fw_info[20];
 } __packed;
 
 struct intel_dmc_header {
@@ -292,6 +291,46 @@ void intel_csr_load_program(struct drm_i915_private *dev_priv)
        gen9_set_dc_state_debugmask(dev_priv);
 }
 
+/*
+ * Search fw_info table for dmc_offset to find firmware binary: num_entries is
+ * already sanitized.
+ */
+static u32 find_dmc_fw_offset(const struct intel_fw_info *fw_info,
+                             unsigned int num_entries,
+                             const struct stepping_info *si)
+{
+       u32 dmc_offset = CSR_DEFAULT_FW_OFFSET;
+       unsigned int i;
+
+       for (i = 0; i < num_entries; i++) {
+               if (fw_info[i].substepping == '*' &&
+                   si->stepping == fw_info[i].stepping) {
+                       dmc_offset = fw_info[i].offset;
+                       break;
+               }
+
+               if (si->stepping == fw_info[i].stepping &&
+                   si->substepping == fw_info[i].substepping) {
+                       dmc_offset = fw_info[i].offset;
+                       break;
+               }
+
+               if (fw_info[i].stepping == '*' &&
+                   fw_info[i].substepping == '*') {
+                       /*
+                        * In theory we should stop the search as generic
+                        * entries should always come after the more specific
+                        * ones, but let's continue to make sure to work even
+                        * with "broken" firmwares. If we don't find a more
+                        * specific one, then we use this entry
+                        */
+                       dmc_offset = fw_info[i].offset;
+               }
+       }
+
+       return dmc_offset;
+}
+
 static u32 *parse_csr_fw(struct drm_i915_private *dev_priv,
                         const struct firmware *fw)
 {
@@ -300,7 +339,7 @@ static u32 *parse_csr_fw(struct drm_i915_private *dev_priv,
        struct intel_dmc_header *dmc_header;
        struct intel_csr *csr = &dev_priv->csr;
        const struct stepping_info *si = intel_get_stepping_info(dev_priv);
-       u32 dmc_offset = CSR_DEFAULT_FW_OFFSET, readcount = 0, nbytes;
+       u32 dmc_offset, num_entries, readcount = 0, nbytes;
        u32 i;
        u32 *dmc_payload;
        size_t fsize;
@@ -349,27 +388,26 @@ static u32 *parse_csr_fw(struct drm_i915_private *dev_priv,
                          (package_header->header_len * 4));
                return NULL;
        }
+
        readcount += sizeof(struct intel_package_header);
+       num_entries = package_header->num_entries;
+       if (WARN_ON(package_header->num_entries > PACKAGE_MAX_FW_INFO_ENTRIES))
+               num_entries = PACKAGE_MAX_FW_INFO_ENTRIES;
 
-       /* Search for dmc_offset to find firware binary. */
-       for (i = 0; i < package_header->num_entries; i++) {
-               if (package_header->fw_info[i].substepping == '*' &&
-                   si->stepping == package_header->fw_info[i].stepping) {
-                       dmc_offset = package_header->fw_info[i].offset;
-                       break;
-               } else if (si->stepping == package_header->fw_info[i].stepping &&
-                          si->substepping == package_header->fw_info[i].substepping) {
-                       dmc_offset = package_header->fw_info[i].offset;
-                       break;
-               } else if (package_header->fw_info[i].stepping == '*' &&
-                          package_header->fw_info[i].substepping == '*')
-                       dmc_offset = package_header->fw_info[i].offset;
-       }
+       fsize += PACKAGE_MAX_FW_INFO_ENTRIES * sizeof(struct intel_fw_info);
+       if (fsize > fw->size)
+               goto error_truncated;
+
+       dmc_offset = find_dmc_fw_offset((struct intel_fw_info *)
+                                       &fw->data[readcount], num_entries, si);
        if (dmc_offset == CSR_DEFAULT_FW_OFFSET) {
                DRM_ERROR("DMC firmware not supported for %c stepping\n",
                          si->stepping);
                return NULL;
        }
+       /* we always have space for PACKAGE_MAX_FW_INFO_ENTRIES */
+       readcount += PACKAGE_MAX_FW_INFO_ENTRIES * sizeof(struct intel_fw_info);
+
        /* Convert dmc_offset into number of bytes. By default it is in dwords*/
        dmc_offset *= 4;
        readcount += dmc_offset;