[PATCH u-boot-mvebu v2 5/5] arm: mvebu: a37xx: Add support for reading Security OTP values

[Pali Rohár]

It is not possible for the A53 core (on which U-Boot is running) to read it
directly. For this purpose Marvell defined mbox API for sending OTP
commands between CM3 and A53 cores.

Implement these Marvell fuse reading mbox commands via U-Boot fuse API.

Banks 0-43 are used for accessing Security OTP (44 rows with 67 bits via 44
banks and words 0-2).

Note that of the 67 bits, the 3 upper bits are: 1 lock bit and 2
auxiliary bits (meant for testing during the manufacture of the SOC, as
I understand it).

Also note that the lock bit and the auxiliary bits are not readable
via Marvell commands.

With CZ.NIC's commands the lock bit is readable.

Write support is not implemented yet.

Signed-off-by: Pali Rohár <pali at kernel.org>
---
 arch/arm/mach-mvebu/armada3700/efuse.c | 38 ++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-mvebu/armada3700/efuse.c b/arch/arm/mach-mvebu/armada3700/efuse.c
index 03778f17ea49..fcf6edd08ce1 100644
--- a/arch/arm/mach-mvebu/armada3700/efuse.c
+++ b/arch/arm/mach-mvebu/armada3700/efuse.c
@@ -8,6 +8,7 @@
 #include <common.h>
 #include <asm/io.h>
 #include <linux/delay.h>
+#include <mach/mbox.h>
 #include <mach/soc.h>
 
 #define OTP_NB_REG_BASE		((void __iomem *)MVEBU_REGISTER(0x12600))
@@ -77,6 +78,40 @@ static void otp_read_parallel(void __iomem *base, u32 *data, u32 count)
 	}
 }
 
+static int rwtm_otp_read(u8 row, u32 word, u32 *data)
+{
+	u32 out[3];
+	u32 in[2];
+	int res = -EINVAL;
+
+	if (word < 2) {
+		/*
+		 * MBOX_CMD_OTP_READ_32B command is supported by Marvell
+		 * fuse.bin firmware and also by new CZ.NIC wtmi firmware.
+		 * This command returns raw bits without ECC corrections.
+		 * It does not provide access to the lock bit.
+		 */
+		in[0] = row;
+		in[1] = word * 32;
+		res = mbox_do_cmd(MBOX_CMD_OTP_READ_32B, in, 2, out, 2);
+		if (!res)
+			*data = out[0];
+	} else if (word == 2) {
+		/*
+		 * MBOX_CMD_OTP_READ command is supported only by CZ.NIC wtmi
+		 * firmware and provide access to all bits, including lock bit.
+		 * But this command does ECC correction of returned bits. So
+		 * use it only for accessing lock bit.
+		 */
+		in[0] = row;
+		res = mbox_do_cmd(MBOX_CMD_OTP_READ, in, 1, out, 3);
+		if (!res)
+			*data = out[2];
+	}
+
+	return res;
+}
+
 /*
  * Banks 0-43 are used for accessing Security OTP (44 rows with 67 bits via 44 banks and words 0-2)
  * Bank 44 is used for accessing North Bridge OTP (69 bits via words 0-2)
@@ -96,8 +131,7 @@ int fuse_read(u32 bank, u32 word, u32 *val)
 	if (bank <= RWTM_MAX_BANK) {
 		if (word >= RWTM_ROW_WORDS)
 			return -EINVAL;
-		/* TODO: not implemented yet */
-		return -ENOSYS;
+		return rwtm_otp_read(bank, word, val);
 	} else if (bank == OTP_NB_BANK) {
 		u32 data[OTP_NB_WORDS];
 		if (word >= OTP_NB_WORDS)
-- 
2.20.1