Merge patch series "cmd: fuse: Introduce fuse writebuff sub-system and clean up"

Harsha Vardhan V M <h-vm@ti.com> says:

This patch series introduces the fuse writebuff sub-system command and
makes improvements to the existing fuse implementation by removing the
custom string functions. The patches are required to be applied in
sequence.

The series consists of the following changes:
Patch 1 removes custom string functions and replaces them with standard
string functions.
Patch 2 introduces fuse.rst documentation for fuse commands.
Patch 3 introduces the fuse writebuff sub-system command, allowing to
write a structured buffer in memory to fuses, and implementing the
necessary function calls.
Patch 4 enables the fuse sub-system in the K3 platform.
Patch 5 updates the fuse.rst documentation to include details about the
new fuse writebuff command.

These changes aim to improve the fuse sub-system by the removal of
custom string functions and the addition of the fuse writebuff
command improves fuse programming workflows by allowing to write a
structured buffer in memory to efuses.

Link: https://lore.kernel.org/r/20250319084714.335777-1-h-vm@ti.com

3 files changed, 86 insertions, 0 deletions

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index da84b35e804..834e0285097 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -468,6 +468,13 @@ config STM32MP_FUSE
 	  for STM32MP architecture.
 	  This API is needed for CMD_FUSE.
 
+config K3_FUSE
+	bool "Enable TI K3 fuse wrapper providing the fuse API"
+	depends on MISC && CMD_FUSE && CMD_FUSE_WRITEBUFF
+	help
+	  If you say Y here, you will get support for the fuse API (OTP)
+	  for TI K3 architecture.
+
 config STM32_RCC
 	bool "Enable RCC driver for the STM32 SoC's family"
 	depends on (ARCH_STM32 || ARCH_STM32MP) && MISC
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index dac805e4cdd..0b81ba2604f 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -48,6 +48,7 @@ obj-$(CONFIG_$(XPL_)I2C_EEPROM) += i2c_eeprom.o
 obj-$(CONFIG_IHS_FPGA) += ihs_fpga.o
 obj-$(CONFIG_IMX8) += imx8/
 obj-$(CONFIG_IMX_ELE) += imx_ele/
+obj-$(CONFIG_K3_FUSE) += k3_fuse.o
 obj-$(CONFIG_LED_STATUS) += status_led.o
 obj-$(CONFIG_LED_STATUS_GPIO) += gpio_led.o
 obj-$(CONFIG_MPC83XX_SERDES) += mpc83xx_serdes.o
diff --git a/drivers/misc/k3_fuse.c b/drivers/misc/k3_fuse.c
new file mode 100644
index 00000000000..4a8ff1f2523
--- /dev/null
+++ b/drivers/misc/k3_fuse.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2025 Texas Instruments Incorporated, <www.ti.com>
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <fuse.h>
+#include <linux/arm-smccc.h>
+#include <string.h>
+
+#define K3_SIP_OTP_WRITEBUFF 0xC2000000
+#define K3_SIP_OTP_WRITE 0xC2000001
+#define K3_SIP_OTP_READ 0xC2000002
+
+int fuse_read(u32 bank, u32 word, u32 *val)
+{
+	struct arm_smccc_res res;
+
+	if (bank != 0U) {
+		printf("Invalid bank argument, ONLY bank 0 is supported\n");
+		return -EINVAL;
+	}
+
+	/* Make SiP SMC call and send the word in the parameter register */
+	arm_smccc_smc(K3_SIP_OTP_READ, word,
+		      0, 0, 0, 0, 0, 0, &res);
+
+	*val = res.a1;
+	if (res.a0 != 0)
+		printf("SMC call failed: Error code %lu\n", res.a0);
+
+	return res.a0;
+}
+
+int fuse_sense(u32 bank, u32 word, u32 *val)
+{
+	return -EPERM;
+}
+
+int fuse_prog(u32 bank, u32 word, u32 val)
+{
+	struct arm_smccc_res res;
+	u32 mask = val;
+
+	if (bank != 0U) {
+		printf("Invalid bank argument, ONLY bank 0 is supported\n");
+		return -EINVAL;
+	}
+
+	/* Make SiP SMC call and send the word, val and mask in the parameter register */
+	arm_smccc_smc(K3_SIP_OTP_WRITE, word,
+		      val, mask, 0, 0, 0, 0, &res);
+
+	if (res.a0 != 0)
+		printf("SMC call failed: Error code %lu\n", res.a0);
+
+	return res.a0;
+}
+
+int fuse_override(u32 bank, u32 word, u32 val)
+{
+	return -EPERM;
+}
+
+int fuse_writebuff(ulong addr)
+{
+	struct arm_smccc_res res;
+
+	/* Make SiP SMC call and send the addr in the parameter register */
+	arm_smccc_smc(K3_SIP_OTP_WRITEBUFF, (unsigned long)addr,
+		      0, 0, 0, 0, 0, 0, &res);
+
+	if (res.a0 != 0)
+		printf("SMC call failed: Error code %lu\n", res.a0);
+
+	return res.a0;
+}