mach-snapdragon: support parsing memory info from external FDT

qcom_parse_memory is updated to return a -ENODATA error if the passed
FDT does not contain a /memory node, or that node is incomplete (size=0)

board_fdt_blob_setup first tries to call qcom_parse_memory with the
internal FDT (if present+valid). If that fails, it tries again with the
external FDT (again, if present+valid).

When booting with an internal FDT from upstream, it's likely that this
change results in a slight performance hit, since virtually all upstream
qcom DTs lack a fully specified memory node. The impact should be
negligible, though.

qcom_parse_memory was given a detailed docstring adapted from Caleb's
original commit message that introduced the function.

Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
Signed-off-by: Sam Day <me@samcday.com>
Link: https://lore.kernel.org/r/20250123-qcom-parse-memory-updates-v3-1-c5332b81ea9f@samcday.com
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 2ef936a..e875517 100644 (file)
--- a/arch/arm/mach-snapdragon/board.c
+++ b/arch/arm/mach-snapdragon/board.c
@@ -88,7 +88,29 @@ int dram_init_banksize(void)
        return 0;
 }
 
-static void qcom_parse_memory(const void *fdt)
+/**
+ * The generic memory parsing code in U-Boot lacks a few things that we
+ * need on Qualcomm:
+ *
+ * 1. It sets gd->ram_size and gd->ram_base to represent a single memory block
+ * 2. setup_dest_addr() later relocates U-Boot to ram_base + ram_size, the end
+ *    of that first memory block.
+ *
+ * This results in all memory beyond U-Boot being unusable in Linux when booting
+ * with EFI.
+ *
+ * Since the ranges in the memory node may be out of order, the only way for us
+ * to correctly determine the relocation address for U-Boot is to parse all
+ * memory regions and find the highest valid address.
+ *
+ * We can't use fdtdec_setup_memory_banksize() since it stores the result in
+ * gd->bd, which is not yet allocated.
+ *
+ * @fdt: FDT blob to parse /memory node from
+ *
+ * Return: 0 on success or -ENODATA if /memory node is missing or incomplete
+ */
+static int qcom_parse_memory(const void *fdt)
 {
        int offset;
        const fdt64_t *memory;
@@ -97,16 +119,12 @@ static void qcom_parse_memory(const void *fdt)
        int i, j, banks;
 
        offset = fdt_path_offset(fdt, "/memory");
-       if (offset < 0) {
-               log_err("No memory node found in device tree!\n");
-               return;
-       }
+       if (offset < 0)
+               return -ENODATA;
 
        memory = fdt_getprop(fdt, offset, "reg", &memsize);
-       if (!memory) {
-               log_err("No memory configuration was provided by the previous bootloader!\n");
-               return;
-       }
+       if (!memory)
+               return -ENODATA;
 
        banks = min(memsize / (2 * sizeof(u64)), (ulong)CONFIG_NR_DRAM_BANKS);
 
@@ -119,7 +137,6 @@ static void qcom_parse_memory(const void *fdt)
        for (i = 0, j = 0; i < banks * 2; i += 2, j++) {
                prevbl_ddr_banks[j].start = get_unaligned_be64(&memory[i]);
                prevbl_ddr_banks[j].size = get_unaligned_be64(&memory[i + 1]);
-               /* SM8650 boards sometimes have empty regions! */
                if (!prevbl_ddr_banks[j].size) {
                        j--;
                        continue;
@@ -127,13 +144,16 @@ static void qcom_parse_memory(const void *fdt)
                ram_end = max(ram_end, prevbl_ddr_banks[j].start + prevbl_ddr_banks[j].size);
        }
 
+       if (!banks || !prevbl_ddr_banks[0].size)
+               return -ENODATA;
+
        /* Sort our RAM banks -_- */
        qsort(prevbl_ddr_banks, banks, sizeof(prevbl_ddr_banks[0]), ddr_bank_cmp);
 
        gd->ram_base = prevbl_ddr_banks[0].start;
        gd->ram_size = ram_end - gd->ram_base;
-       debug("ram_base = %#011lx, ram_size = %#011llx, ram_end = %#011llx\n",
-             gd->ram_base, gd->ram_size, ram_end);
+
+       return 0;
 }
 
 static void show_psci_version(void)
@@ -153,13 +173,14 @@ static void show_psci_version(void)
  */
 int board_fdt_blob_setup(void **fdtp)
 {
-       struct fdt_header *fdt;
+       struct fdt_header *external_fdt, *internal_fdt;
        bool internal_valid, external_valid;
-       int ret = 0;
+       int ret = -ENODATA;
 
-       fdt = (struct fdt_header *)get_prev_bl_fdt_addr();
-       external_valid = fdt && !fdt_check_header(fdt);
-       internal_valid = !fdt_check_header(*fdtp);
+       internal_fdt = (struct fdt_header *)*fdtp;
+       external_fdt = (struct fdt_header *)get_prev_bl_fdt_addr();
+       external_valid = external_fdt && !fdt_check_header(external_fdt);
+       internal_valid = !fdt_check_header(internal_fdt);
 
        /*
         * There is no point returning an error here, U-Boot can't do anything useful in this situation.
@@ -167,24 +188,36 @@ int board_fdt_blob_setup(void **fdtp)
         */
        if (!internal_valid && !external_valid)
                panic("Internal FDT is invalid and no external FDT was provided! (fdt=%#llx)\n",
-                     (phys_addr_t)fdt);
+                     (phys_addr_t)external_fdt);
+
+       /* Prefer memory information from internal DT if it's present */
+       if (internal_valid)
+               ret = qcom_parse_memory(internal_fdt);
+
+       if (ret < 0 && external_valid) {
+               /* No internal FDT or it lacks a proper /memory node.
+                * The previous bootloader handed us something, let's try that.
+                */
+               if (internal_valid)
+                       debug("No memory info in internal FDT, falling back to external\n");
+
+               ret = qcom_parse_memory(external_fdt);
+       }
+
+       if (ret < 0)
+               panic("No valid memory ranges found!\n");
+
+       debug("ram_base = %#011lx, ram_size = %#011llx\n",
+             gd->ram_base, gd->ram_size);
 
        if (internal_valid) {
                debug("Using built in FDT\n");
-               ret = -EEXIST;
-       } else {
-               debug("Using external FDT\n");
-               /* So we can use it before returning */
-               *fdtp = fdt;
+               return -EEXIST;
        }
 
-       /*
-        * Parse the /memory node while we're here,
-        * this makes it easy to do other things early.
-        */
-       qcom_parse_memory(*fdtp);
-
-       return ret;
+       debug("Using external FDT\n");
+       *fdtp = external_fdt;
+       return 0;
 }
 
 void reset_cpu(void)