[PATCH v4 22/39] mach-snapdragon: generate fdtfile automatically

[Sumit Garg]

On Fri, 16 Feb 2024 at 02:22, Caleb Connolly <caleb.connolly at linaro.org> 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.
>
> Reviewed-by: Neil Armstrong <neil.armstrong at linaro.org>
> Signed-off-by: Caleb Connolly <caleb.connolly at linaro.org>
> ---
>  arch/arm/mach-snapdragon/board.c | 101 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 101 insertions(+)
>

Reviewed-by: Sumit Garg <sumit.garg at linaro.org>

-Sumit

> diff --git a/arch/arm/mach-snapdragon/board.c b/arch/arm/mach-snapdragon/board.c
> index f445bed3af00..5a859aabd5c4 100644
> --- 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;
>
> --
> 2.43.1
>