arm: boot: Add board specific setup code API

Add an API for boards to inject their own preboot software (or
firmware) sequence.

The software then returns to the bootloader via the link register. This
allows boards to do their own little bits of firmware setup without
needed to replace the bootloader completely (which is the requirement
for existing firmware support).

The blob is loaded by a callback if and only if doing a linux boot
(similar to the existing write_secondary support).

Rewrite the comment for the primary boot blob.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Message-id: 070295644c6ac84696d743913296e8cfefb48c15.1446182614.git.crosthwaite.peter@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 19 insertions, 1 deletions

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 2a151e2..b0879a5 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -31,6 +31,7 @@ typedef enum {
     FIXUP_NONE = 0,     /* do nothing */
     FIXUP_TERMINATOR,   /* end of insns */
     FIXUP_BOARDID,      /* overwrite with board ID number */
+    FIXUP_BOARD_SETUP,  /* overwrite with board specific setup code address */
     FIXUP_ARGPTR,       /* overwrite with pointer to kernel args */
     FIXUP_ENTRYPOINT,   /* overwrite with kernel entry point */
     FIXUP_GIC_CPU_IF,   /* overwrite with GIC CPU interface address */
@@ -58,8 +59,17 @@ static const ARMInsnFixup bootloader_aarch64[] = {
     { 0, FIXUP_TERMINATOR }
 };
 
-/* The worlds second smallest bootloader.  Set r0-r2, then jump to kernel.  */
+/* A very small bootloader: call the board-setup code (if needed),
+ * set r0-r2, then jump to the kernel.
+ * If we're not calling boot setup code then we don't copy across
+ * the first BOOTLOADER_NO_BOARD_SETUP_OFFSET insns in this array.
+ */
+
 static const ARMInsnFixup bootloader[] = {
+    { 0xe28fe008 }, /* add     lr, pc, #8 */
+    { 0xe51ff004 }, /* ldr     pc, [pc, #-4] */
+    { 0, FIXUP_BOARD_SETUP },
+#define BOOTLOADER_NO_BOARD_SETUP_OFFSET 3
     { 0xe3a00000 }, /* mov     r0, #0 */
     { 0xe59f1004 }, /* ldr     r1, [pc, #4] */
     { 0xe59f2004 }, /* ldr     r2, [pc, #4] */
@@ -131,6 +141,7 @@ static void write_bootloader(const char *name, hwaddr addr,
         case FIXUP_NONE:
             break;
         case FIXUP_BOARDID:
+        case FIXUP_BOARD_SETUP:
         case FIXUP_ARGPTR:
         case FIXUP_ENTRYPOINT:
         case FIXUP_GIC_CPU_IF:
@@ -640,6 +651,9 @@ static void arm_load_kernel_notify(Notifier *notifier, void *data)
         elf_machine = EM_AARCH64;
     } else {
         primary_loader = bootloader;
+        if (!info->write_board_setup) {
+            primary_loader += BOOTLOADER_NO_BOARD_SETUP_OFFSET;
+        }
         kernel_load_offset = KERNEL_LOAD_ADDR;
         elf_machine = EM_ARM;
     }
@@ -745,6 +759,7 @@ static void arm_load_kernel_notify(Notifier *notifier, void *data)
         info->initrd_size = initrd_size;
 
         fixupcontext[FIXUP_BOARDID] = info->board_id;
+        fixupcontext[FIXUP_BOARD_SETUP] = info->board_setup_addr;
 
         /* for device tree boot, we pass the DTB directly in r2. Otherwise
          * we point to the kernel args.
@@ -793,6 +808,9 @@ static void arm_load_kernel_notify(Notifier *notifier, void *data)
         if (info->nb_cpus > 1) {
             info->write_secondary_boot(cpu, info);
         }
+        if (info->write_board_setup) {
+            info->write_board_setup(cpu, info);
+        }
 
         /* Notify devices which need to fake up firmware initialization
          * that we're doing a direct kernel boot.