mach-snapdragon: generate fdtfile automatically

With just a few basic rules, we can generate the $fdtfile environment
variable to match the format used in Linux. This uses the root
compatible property inside u-boot, with specific handling for the
Dragonboard845c which is a special case, and for the qrb robotics
boards.

This is known to work on supported platforms, and lets us avoid having a
big lookup table.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Sumit Garg <sumit.garg@linaro.org> #qcs404
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>

diff --git a/arch/arm/mach-snapdragon/board.c b/arch/arm/mach-snapdragon/board.c
index f445bed3af00563b50afb7299bbfb593f2e0a7c2..5a859aabd5c4d56aeb89ac5c34be5ad052e69140 100644 (file)
--- a/arch/arm/mach-snapdragon/board.c
+++ b/arch/arm/mach-snapdragon/board.c
@@ -160,6 +160,106 @@ int board_init(void)
        return 0;
 }
 
+/* Sets up the "board", and "soc" environment variables as well as constructing the devicetree
+ * path, with a few quirks to handle non-standard dtb filenames. This is not meant to be a
+ * comprehensive solution to automatically picking the DTB, but aims to be correct for the
+ * majority case. For most devices it should be possible to make this algorithm work by
+ * adjusting the root compatible property in the U-Boot DTS. Handling devices with multiple
+ * variants that are all supported by a single U-Boot image will require implementing device-
+ * specific detection.
+ */
+static void configure_env(void)
+{
+       const char *first_compat, *last_compat;
+       char *tmp;
+       char buf[32] = { 0 };
+       /*
+        * Most DTB filenames follow the scheme: qcom/<soc>-[vendor]-<board>.dtb
+        * The vendor is skipped when it's a Qualcomm reference board, or the
+        * db845c.
+        */
+       char dt_path[64] = { 0 };
+       int compat_count, ret;
+       ofnode root;
+
+       root = ofnode_root();
+       /* This is almost always 2, but be explicit that we want the first and last compatibles
+        * not the first and second.
+        */
+       compat_count = ofnode_read_string_count(root, "compatible");
+       if (compat_count < 2) {
+               log_warning("%s: only one root compatible bailing!\n", __func__);
+               return;
+       }
+
+       /* The most specific device compatible (e.g. "thundercomm,db845c") */
+       ret = ofnode_read_string_index(root, "compatible", 0, &first_compat);
+       if (ret < 0) {
+               log_warning("Can't read first compatible\n");
+               return;
+       }
+
+       /* The last compatible is always the SoC compatible */
+       ret = ofnode_read_string_index(root, "compatible", compat_count - 1, &last_compat);
+       if (ret < 0) {
+               log_warning("Can't read second compatible\n");
+               return;
+       }
+
+       /* Copy the second compat (e.g. "qcom,sdm845") into buf */
+       strlcpy(buf, last_compat, sizeof(buf) - 1);
+       tmp = buf;
+
+       /* strsep() is destructive, it replaces the comma with a \0 */
+       if (!strsep(&tmp, ",")) {
+               log_warning("second compatible '%s' has no ','\n", buf);
+               return;
+       }
+
+       /* tmp now points to just the "sdm845" part of the string */
+       env_set("soc", tmp);
+
+       /* Now figure out the "board" part from the first compatible */
+       memset(buf, 0, sizeof(buf));
+       strlcpy(buf, first_compat, sizeof(buf) - 1);
+       tmp = buf;
+
+       /* The Qualcomm reference boards (RBx, HDK, etc)  */
+       if (!strncmp("qcom", buf, strlen("qcom"))) {
+               /*
+                * They all have the first compatible as "qcom,<soc>-<board>"
+                * (e.g. "qcom,qrb5165-rb5"). We extract just the part after
+                * the dash.
+                */
+               if (!strsep(&tmp, "-")) {
+                       log_warning("compatible '%s' has no '-'\n", buf);
+                       return;
+               }
+               /* tmp is now "rb5" */
+               env_set("board", tmp);
+       } else {
+               if (!strsep(&tmp, ",")) {
+                       log_warning("compatible '%s' has no ','\n", buf);
+                       return;
+               }
+               /* for thundercomm we just want the bit after the comma (e.g. "db845c"),
+                * for all other boards we replace the comma with a '-' and take both
+                * (e.g. "oneplus-enchilada")
+                */
+               if (!strncmp("thundercomm", buf, strlen("thundercomm"))) {
+                       env_set("board", tmp);
+               } else {
+                       *(tmp - 1) = '-';
+                       env_set("board", buf);
+               }
+       }
+
+       /* Now build the full path name */
+       snprintf(dt_path, sizeof(dt_path), "qcom/%s-%s.dtb",
+                env_get("soc"), env_get("board"));
+       env_set("fdtfile", dt_path);
+}
+
 void __weak qcom_late_init(void)
 {
 }
@@ -188,6 +288,7 @@ int board_late_init(void)
        if (status)
                log_warning("%s: Failed to set run time variables\n", __func__);
 
+       configure_env();
        qcom_late_init();
 
        return 0;