spi25_statusreg.c: support reading security register

Not to be confused with "secure registers" of OTP.

Security register is a dedicated status register for security-related
bits. You don't write its value directly, issuing special write commands
with no data set separate OTP bits to 1 automatically (WRSCUR, WPSEL
commands). No WREN is necessary, but at least some datasheets indicate
BUSY state after those write commands.

Unlike cases where OTP bit is part of SR and can only be written while
in OTP mode, security register can only be written outside of the mode.

The register is found in at least these chips by Macronix:
 * MX25L6436E
 * MX25L6445E
 * MX25L6465E
 * MX25L6473E

Change-Id: Iae1753ca4cb051127a5bcbeba7f064053adb8dae
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/59709
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Nikolai Artemiev <nartemiev@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/spi25_statusreg.c b/spi25_statusreg.c
index d0ce8597a..2859b2320 100644
--- a/spi25_statusreg.c
+++ b/spi25_statusreg.c
@@ -100,6 +100,13 @@ int spi_write_register(const struct flashctx *flash, enum flash_reg reg, uint8_t
 		}
 		msg_cerr("Cannot write SR3: unsupported by chip\n");
 		return 1;
+	case SECURITY:
+		/*
+		 * Security register doesn't have a normal write operation. Instead,
+		 * there are separate commands that set individual OTP bits.
+		 */
+		msg_cerr("Cannot write SECURITY: unsupported by design\n");
+		return 1;
 	default:
 		msg_cerr("Cannot write register: unknown register\n");
 		return 1;
@@ -195,6 +202,13 @@ int spi_read_register(const struct flashctx *flash, enum flash_reg reg, uint8_t
 		}
 		msg_cerr("Cannot read SR3: unsupported by chip\n");
 		return 1;
+	case SECURITY:
+		if (feature_bits & FEATURE_SCUR) {
+			read_cmd = JEDEC_RDSCUR;
+			break;
+		}
+		msg_cerr("Cannot read SECURITY: unsupported by chip\n");
+		return 1;
 	default:
 		msg_cerr("Cannot read register: unknown register\n");
 		return 1;