[PATCH V2 2/2] ARM: imx: Pick correct eMMC boot partition from ROM log

[Marek Vasut]

In case the iMX8M boot from eMMC boot partition and the primary image
is corrupted, the BootROM is capable of starting a secondary image in
the other eMMC boot partition as a fallback.

However, the BootROM leaves the eMMC BOOT_PARTITION_ENABLE setting as
it was, i.e. pointing to the boot partition containing the corrupted
image, and the BootROM does not provide any indication that this sort
of fallback occured.

According to AN12853 i.MX ROMs Log Events, Rev. 0, May 2020, it is
possible to determine whether fallback event occurred by parsing the
ROM event log. In case ROM event ID 0x51 is present, fallback event
did occur.

This patch implements ROM event log parsing and search for event ID
0x51 for all iMX8M SoCs, and based on that corrects the eMMC boot
partition selection. This way, the SPL loads the remaining boot
components from the same eMMC boot partition from which it was
started, even in case of the fallback.

Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Faiz Abbas <faiz_abbas at ti.com>
Cc: Harald Seiler <hws at denx.de>
Cc: Lokesh Vutla <lokeshvutla at ti.com>
Cc: Simon Glass <sjg at chromium.org>
Cc: Fabio Estevam <festevam at gmail.com>
Cc: Peng Fan <peng.fan at nxp.com>
Cc: Stefano Babic <sbabic at denx.de>
Cc: Ye Li <ye.li at nxp.com>
---
V2: Return detected partition when the end of ROM event log is reached.
---
 arch/arm/mach-imx/imx8m/soc.c | 61 +++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/arch/arm/mach-imx/imx8m/soc.c b/arch/arm/mach-imx/imx8m/soc.c
index 0c44022a6dc..f8ff4332d86 100644
--- a/arch/arm/mach-imx/imx8m/soc.c
+++ b/arch/arm/mach-imx/imx8m/soc.c
@@ -571,6 +571,67 @@ enum boot_device get_boot_device(void)
 }
 #endif
 
+#if defined(CONFIG_IMX8M)
+#include <spl.h>
+int spl_mmc_emmc_boot_partition(struct mmc *mmc)
+{
+	u32 *rom_log_addr = (u32 *)0x9e0;
+	u32 *rom_log;
+	u8 event_id;
+	int i, part;
+
+	part = default_spl_mmc_emmc_boot_partition(mmc);
+
+	/* If the ROM event log pointer is not valid. */
+	if (*rom_log_addr < 0x900000 || *rom_log_addr >= 0xb00000 ||
+	    *rom_log_addr & 0x3)
+		return part;
+
+	/* Parse the ROM event ID version 2 log */
+	rom_log = (u32 *)(uintptr_t)(*rom_log_addr);
+	for (i = 0; i < 128; i++) {
+		event_id = rom_log[i] >> 24;
+		switch (event_id) {
+		case 0x00: /* End of list */
+			return part;
+		/* Log entries with 1 parameter, skip 1 */
+		case 0x80: /* Start to perform the device initialization */
+		case 0x81: /* The boot device initialization completes */
+		case 0x8f: /* The boot device initialization fails */
+		case 0x90: /* Start to read data from boot device */
+		case 0x91: /* Reading data from boot device completes */
+		case 0x9f: /* Reading data from boot device fails */
+			i += 1;
+			continue;
+		/* Log entries with 2 parameters, skip 2 */
+		case 0xa0: /* Image authentication result */
+		case 0xc0: /* Jump to the boot image soon */
+			i += 2;
+			continue;
+		/* Boot from the secondary boot image */
+		case 0x51:
+			/*
+			 * Swap the eMMC boot partitions in case there was a
+			 * fallback event (i.e. primary image was corrupted
+			 * and that corruption was recognized by the BootROM),
+			 * so the SPL loads the rest of the U-Boot from the
+			 * correct eMMC boot partition, since the BootROM
+			 * leaves the boot partition set to the corrupted one.
+			 */
+			if (part == 1)
+				part = 2;
+			else if (part == 2)
+				part = 1;
+			continue;
+		default:
+			continue;
+		}
+	}
+
+	return part;
+}
+#endif
+
 bool is_usb_boot(void)
 {
 	return get_boot_device() == USB_BOOT;
-- 
2.30.2