[PATCH u-boot-marvell 3/3] arm: mvebu: turris_omnia: Switch DDR speed to 1333H when reset 9 is selected

["Marek Behún" <kabel@kernel.org>]

Users experiencing random kernel crashes due to new versions of
Marvell's DDR training algorithm can solve the issue by setting DDR
speed to 1333H.

But if kernel crashes, it has to be done in U-Boot, which is impossible
without UART connection.

In order to make it easier for users, use the rescue button mechanism:
when rescue mode 9 is selected (that is when 10 LEDs are ON), U-Boot
will train DDR in 1333H mode and also update EEPROM so that subsequent
boot will use this mode.

User has to use the `eeprom` command in U-Boot or `omnia-eeprom` command
in OS to switch back to 1600K mode.

Signed-off-by: Marek Behún <kabel@kernel.org>
---
 board/CZ.NIC/turris_omnia/turris_omnia.c | 90 ++++++++++++++++++++----
 1 file changed, 77 insertions(+), 13 deletions(-)

diff --git a/board/CZ.NIC/turris_omnia/turris_omnia.c b/board/CZ.NIC/turris_omnia/turris_omnia.c
index 46f20f05c05..eb88ee7f1ed 100644
--- a/board/CZ.NIC/turris_omnia/turris_omnia.c
+++ b/board/CZ.NIC/turris_omnia/turris_omnia.c
@@ -47,6 +47,9 @@ DECLARE_GLOBAL_DATA_PTR;
 #define OMNIA_I2C_EEPROM_CHIP_LEN	2
 #define OMNIA_I2C_EEPROM_MAGIC		0x0341a034
 
+#define OMNIA_RESET_TO_LOWER_DDR_SPEED	9
+#define OMNIA_LOWER_DDR_SPEED		"1333H"
+
 #define A385_SYS_RSTOUT_MASK		MVEBU_REGISTER(0x18260)
 #define   A385_SYS_RSTOUT_MASK_WD	BIT(10)
 
@@ -206,6 +209,20 @@ static u32 omnia_mcu_crc32(const void *p, size_t len)
 	return ~bitrev32(crc);
 }
 
+static int omnia_mcu_get_reset(void)
+{
+	u8 reset_status;
+	int ret;
+
+	ret = omnia_mcu_read(CMD_GET_RESET, &reset_status, 1);
+	if (ret) {
+		printf("omnia_mcu_read failed: %i, reset status unknown!\n", ret);
+		return ret;
+	}
+
+	return reset_status;
+}
+
 /* Can only be called after relocation, since it needs cleared BSS */
 static int omnia_mcu_board_info(char *serial, u8 *mac, char *version)
 {
@@ -463,14 +480,17 @@ static bool check_eeprom_crc(const void *buf, size_t size, u32 expected,
 	return true;
 }
 
+static struct udevice *omnia_get_eeprom(void)
+{
+	return omnia_get_i2c_chip("EEPROM", OMNIA_I2C_EEPROM_CHIP_ADDR,
+				  OMNIA_I2C_EEPROM_CHIP_LEN);
+}
+
 static bool omnia_read_eeprom(struct omnia_eeprom *oep)
 {
-	struct udevice *eeprom;
+	struct udevice *eeprom = omnia_get_eeprom();
 	int ret;
 
-	eeprom = omnia_get_i2c_chip("EEPROM", OMNIA_I2C_EEPROM_CHIP_ADDR,
-				    OMNIA_I2C_EEPROM_CHIP_LEN);
-
 	if (!eeprom)
 		return false;
 
@@ -502,6 +522,35 @@ static bool omnia_read_eeprom(struct omnia_eeprom *oep)
 	return true;
 }
 
+static void omnia_eeprom_set_lower_ddr_speed(void)
+{
+	struct udevice *eeprom = omnia_get_eeprom();
+	struct omnia_eeprom oep;
+	int ret;
+
+	if (!eeprom || !omnia_read_eeprom(&oep))
+		return;
+
+	puts("Setting DDR speed to " OMNIA_LOWER_DDR_SPEED " in EEPROM as requested by reset button... ");
+
+	/* check if already set */
+	if (!strncmp(oep.ddr_speed, OMNIA_LOWER_DDR_SPEED, sizeof(oep.ddr_speed)) &&
+	    (oep.old_ddr_training == 0 || oep.old_ddr_training == 0xff)) {
+		puts("was already set\n");
+		return;
+	}
+
+	strncpy(oep.ddr_speed, OMNIA_LOWER_DDR_SPEED, sizeof(oep.ddr_speed));
+	oep.old_ddr_training = 0xff;
+	oep.crc2 = crc32(0, (const void *)&oep, offsetof(struct omnia_eeprom, crc2));
+
+	ret = i2c_eeprom_write(eeprom, 0, (const void *)&oep, sizeof(oep));
+	if (ret)
+		printf("cannot write EEPROM: %d\n", ret);
+	else
+		puts("done\n");
+}
+
 int omnia_get_ram_size_gb(void)
 {
 	static int ram_size;
@@ -531,6 +580,13 @@ bool board_use_old_ddr3_training(void)
 {
 	struct omnia_eeprom oep;
 
+	/*
+	 * If lower DDR speed is requested by reset button, we can't use old DDR
+	 * training algorithm.
+	 */
+	if (omnia_mcu_get_reset() == OMNIA_RESET_TO_LOWER_DDR_SPEED)
+		return false;
+
 	if (!omnia_read_eeprom(&oep))
 		return false;
 
@@ -711,13 +767,19 @@ static void fixup_speed_in_ddr_topology(struct mv_ddr_topology_map *topology)
 	const struct omnia_ddr_speed *setting;
 	const char *speed;
 	static bool done;
+	int reset_status;
 
 	if (done)
 		return;
 
 	done = true;
 
-	speed = omnia_get_ddr_speed();
+	reset_status = omnia_mcu_get_reset();
+	if (reset_status == OMNIA_RESET_TO_LOWER_DDR_SPEED)
+		speed = OMNIA_LOWER_DDR_SPEED;
+	else
+		speed = omnia_get_ddr_speed();
+
 	if (!speed)
 		return;
 
@@ -734,7 +796,10 @@ static void fixup_speed_in_ddr_topology(struct mv_ddr_topology_map *topology)
 	if (params->speed_bin_index == setting->speed_bin)
 		return;
 
-	printf("Fixing up DDR3 speed (EEPROM defines %s)\n", speed);
+	if (reset_status == OMNIA_RESET_TO_LOWER_DDR_SPEED)
+		printf("Fixing up DDR3 speed to %s as requested by reset button\n", speed);
+	else
+		printf("Fixing up DDR3 speed (EEPROM defines %s)\n", speed);
 
 	params->speed_bin_index = setting->speed_bin;
 	params->memory_freq = setting->freq;
@@ -771,8 +836,7 @@ static int set_regdomain(void)
 static void handle_reset_button(void)
 {
 	const char * const vars[1] = { "bootcmd_rescue", };
-	int ret;
-	u8 reset_status;
+	int reset_status;
 
 	/*
 	 * Ensure that bootcmd_rescue has always stock value, so that running
@@ -781,12 +845,12 @@ static void handle_reset_button(void)
 	 */
 	env_set_default_vars(1, (char * const *)vars, 0);
 
-	ret = omnia_mcu_read(CMD_GET_RESET, &reset_status, 1);
-	if (ret) {
-		printf("omnia_mcu_read failed: %i, reset status unknown!\n",
-		       ret);
+	reset_status = omnia_mcu_get_reset();
+	if (reset_status < 0)
 		return;
-	}
+
+	if (reset_status == OMNIA_RESET_TO_LOWER_DDR_SPEED)
+		return omnia_eeprom_set_lower_ddr_speed();
 
 	env_set_ulong("omnia_reset", reset_status);
 
-- 
2.44.2