Allow configuring bootargs at runtime

Author: object-Object

linux/buildroot/opensbi/compile_flags.txt

@@ -1,3 +1,4 @@
 -I../../../../opensbi/include
+-I../../../../opensbi/lib/utils/libfdt
 -I./mlogv32
 --target=riscv32-linux-gnu

linux/buildroot/opensbi/platform/mlogv32/Kconfig

@@ -9,6 +9,7 @@
 #
 config PLATFORM_MLOGV32
 	bool
+	select FDT
 	select SERIAL_XILINX_UARTLITE
 	select TIMER_MTIMER
 	default y

linux/buildroot/opensbi/platform/mlogv32/platform.c

@@ -4,11 +4,18 @@
  * Copyright (c) 2019 Western Digital Corporation or its affiliates.
  */
 
+#include <libfdt.h>
+
 #include <sbi/riscv_asm.h>
 #include <sbi/riscv_encoding.h>
+#include <sbi/sbi_console.h>
 #include <sbi/sbi_const.h>
+#include <sbi/sbi_error.h>
 #include <sbi/sbi_platform.h>
+#include <sbi/sbi_timer.h>
 
+#include <sbi_utils/fdt/fdt_fixup.h>
+#include <sbi_utils/fdt/fdt_helper.h>
 #include <sbi_utils/serial/xlnx_uartlite.h>
 #include <sbi_utils/timer/aclint_mtimer.h>
 
@@ -41,6 +48,97 @@ static int mlogv32_early_init(bool cold_boot)
 	return xlnx_uartlite_init(MLOGV32_UART0_ADDR);
 }
 
+static char mlogv32_bootargs[256];
+
+static void mlogv32_do_fixup(struct fdt_general_fixup* f, void* fdt) {
+	if (!mlogv32_bootargs[0])
+		return;
+
+	int chosen_offset = fdt_path_offset(fdt, "/chosen");
+	if (chosen_offset < 0)
+		return;
+
+	int err = fdt_setprop_string(fdt, chosen_offset, "bootargs", mlogv32_bootargs);
+	if (err)
+		sbi_printf("Failed to set bootargs: %s", fdt_strerror(err));
+}
+
+static struct fdt_general_fixup mlogv32_fixup = {
+	.name = "mlogv32-fixup",
+	.do_fixup = mlogv32_do_fixup,
+};
+
+static bool mlogv32_wait_for_input(void* arg) {
+	return sbi_getc() >= 0;
+}
+
+static bool mlogv32_prompt_interrupt_boot(void) {
+	bool retval = false;
+	sbi_printf("Press any key to interrupt boot");
+	for (int i = 0; i < 3; i++) {
+		sbi_printf(".");
+		if (sbi_timer_waitms_until(mlogv32_wait_for_input, NULL, 1000)) {
+			retval = true;
+			break;
+		}
+	}
+	sbi_printf("\n");
+	return retval;
+}
+
+static const char* mlogv32_get_fdt_bootargs(void* fdt) {
+	int chosen_offset = fdt_path_offset(fdt, "/chosen");
+	if (chosen_offset < 0)
+		return NULL;
+
+	return fdt_getprop(fdt, chosen_offset, "bootargs", NULL);
+}
+
+static void mlogv32_prompt_get_bootargs(void* fdt) {
+	// drain input buffer
+	while (mlogv32_wait_for_input(NULL)) {}
+
+	const char* current_bootargs = mlogv32_get_fdt_bootargs(fdt);
+	if (current_bootargs)
+		sbi_printf("Bootargs: %s\n", current_bootargs);
+
+	if (!mlogv32_prompt_interrupt_boot())
+		return;
+
+	while (mlogv32_wait_for_input(NULL)) {}
+
+	sbi_printf("Enter new bootargs: ");
+
+	char* retval = mlogv32_bootargs;
+	int maxwidth = sizeof(mlogv32_bootargs);
+	while (maxwidth > 1) {
+		int ch = sbi_getc();
+		if (ch <= 0)
+			continue;
+
+		// backspace
+		if (ch == 127) {
+			if (retval > mlogv32_bootargs) {
+				sbi_puts("\b \b");
+				retval--;
+				maxwidth++;
+			}
+			continue;
+		}
+
+		sbi_putc(ch);
+
+		if (ch == '\r' || ch == '\n') {
+			break;
+		}
+
+		*retval = (char)ch;
+		retval++;
+		maxwidth--;
+	}
+	*retval = '\0';
+}
+
 /*
  * Platform final initialization.
  */
@@ -49,6 +147,20 @@ static int mlogv32_final_init(bool cold_boot)
 	// delegate UART interrupts to S-mode
 	csr_set(CSR_MIDELEG, MIP_MEIP);
 
+	if (!cold_boot)
+		return 0;
+
+	void* fdt = fdt_get_address_rw();
+
+	mlogv32_prompt_get_bootargs(fdt);
+	sbi_printf("\n\n");
+
+	int rc = fdt_register_general_fixup(&mlogv32_fixup);
+	if (rc && rc != SBI_EALREADY)
+		return rc;
+
+	fdt_fixups(fdt);
+
 	return 0;
 }
 
@@ -69,6 +181,7 @@ const struct sbi_platform_operations platform_ops = {
 	.final_init		= mlogv32_final_init,
 	.timer_init		= mlogv32_timer_init
 };
+
 const struct sbi_platform platform = {
 	.opensbi_version	= OPENSBI_VERSION,
 	.platform_version	= SBI_PLATFORM_VERSION(0x0, 0x00),