arm_fpga: Support uploading a custom command line
The command line for BL33 payloads is typically taken from the DTB. On
"normal" systems the bootloader will put the right version in there, but
we typically don't use one on the FPGAs.
To avoid editing (and possibly re-packaging) the DTB for every change in
the command line, try to read it from some "magic" memory location
instead. It can be easily placed there by the tool that uploads the
other payloads to the FPGA's memory. BL31 will then replace the existing
command line in the DTB with that new string.
To avoid reading garbage, check the memory location for containing a
magic value. This is conveniently chosen to be a simple ASCII string, so
it can just preceed the actual command line in a text file:
--------------------------------
CMD:console=ttyAMA0,38400n8 debug loglevel=8
--------------------------------
Change-Id: I5923a80332c9fac3b4afd1a6aaa321233d0f60da
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/plat/arm/board/arm_fpga/fpga_bl31_setup.c b/plat/arm/board/arm_fpga/fpga_bl31_setup.c
index 6eeff45..9db107c 100644
--- a/plat/arm/board/arm_fpga/fpga_bl31_setup.c
+++ b/plat/arm/board/arm_fpga/fpga_bl31_setup.c
@@ -128,6 +128,84 @@
FPGA_DEFAULT_TIMER_FREQUENCY);
}
+static void fpga_prepare_dtb(void)
+{
+ void *fdt = (void *)(uintptr_t)FPGA_PRELOADED_DTB_BASE;
+ const char *cmdline = (void *)(uintptr_t)FPGA_PRELOADED_CMD_LINE;
+ int err;
+
+ err = fdt_open_into(fdt, fdt, FPGA_MAX_DTB_SIZE);
+ if (err < 0) {
+ ERROR("cannot open devicetree at %p: %d\n", fdt, err);
+ panic();
+ }
+
+ /* Check for the command line signature. */
+ if (!strncmp(cmdline, "CMD:", 4)) {
+ int chosen;
+
+ INFO("using command line at 0x%x\n", FPGA_PRELOADED_CMD_LINE);
+
+ chosen = fdt_add_subnode(fdt, 0, "chosen");
+ if (chosen == -FDT_ERR_EXISTS) {
+ chosen = fdt_path_offset(fdt, "/chosen");
+ }
+ if (chosen < 0) {
+ ERROR("cannot find /chosen node: %d\n", chosen);
+ } else {
+ const char *eol;
+ char nul = 0;
+ int slen;
+
+ /*
+ * There is most likely an EOL at the end of the
+ * command line, make sure we terminate the line there.
+ * We can't replace the EOL with a NUL byte in the
+ * source, as this is in read-only memory. So we first
+ * create the property without any termination, then
+ * append a single NUL byte.
+ */
+ eol = strchr(cmdline, '\n');
+ if (!eol) {
+ eol = strchr(cmdline, 0);
+ }
+ /* Skip the signature and omit the EOL/NUL byte. */
+ slen = eol - (cmdline + 4);
+
+ /*
+ * Let's limit the size of the property, just in case
+ * we find the signature by accident. The Linux kernel
+ * limits to 4096 characters at most (in fact 2048 for
+ * arm64), so that sounds like a reasonable number.
+ */
+ if (slen > 4095) {
+ slen = 4095;
+ }
+ err = fdt_setprop(fdt, chosen, "bootargs",
+ cmdline + 4, slen);
+ if (!err) {
+ err = fdt_appendprop(fdt, chosen, "bootargs",
+ &nul, 1);
+ }
+ if (err) {
+ ERROR("Could not set command line: %d\n", err);
+ }
+ }
+ }
+
+ err = fdt_pack(fdt);
+ if (err < 0) {
+ ERROR("Failed to pack Device Tree at %p: error %d\n", fdt, err);
+ }
+
+ clean_dcache_range((uintptr_t)fdt, fdt_blob_size(fdt));
+}
+
+void bl31_plat_runtime_setup(void)
+{
+ fpga_prepare_dtb();
+}
+
void bl31_plat_enable_mmu(uint32_t flags)
{
/* TODO: determine if MMU needs to be enabled */