Re: [PATCH v2 17/32] mach-snapdragon: generate fdtfile automatically

On 19/12/2023 17:04, Caleb Connolly wrote:

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.

Signed-off-by: Caleb Connolly caleb.connolly@linaro.org

arch/arm/mach-snapdragon/board.c | 101 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+)

diff --git a/arch/arm/mach-snapdragon/board.c b/arch/arm/mach-snapdragon/board.c index b00f536d38b4..752166ea7563 100644 --- a/arch/arm/mach-snapdragon/board.c +++ b/arch/arm/mach-snapdragon/board.c @@ -113,6 +113,106 @@ 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) { }

@@ -142,6 +242,7 @@ 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;

Nice, hope it will still fit for all future boards!

Reviewed-by: Neil Armstrong neil.armstrong@linaro.org