mlxbf-bootctl: Add sysfs file for BlueField boot log

This commit adds sysfs interface to be used to write into the
boot log which is 1KB HW buffer on BlueField SoC. The same log
buffer is also used by firmware code like ATF/UEFI, and can be
displayed by userspace tools or from external host via USB/PCIe.
Signed-off-by: Liming Sun <limings@nvidia.com>
Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
Link: https://lore.kernel.org/r/20230511144924.171585-1-limings@nvidia.comReviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Documentation/ABI/testing/sysfs-platform-mellanox-bootctl

@@ -75,3 +75,12 @@ KernelVersion:	6.4
 Contact:	"Liming Sun <limings@nvidia.com>"
 Description:
 		The file used to access the BlueField boot fifo.
+
+What:		/sys/bus/platform/devices/MLNXBF04:00/rsh_log
+Date:		May 2023
+KernelVersion:	6.4
+Contact:	"Liming Sun <limings@nvidia.com>"
+Description:
+		The file used to write BlueField boot log with the format
+                "[INFO|WARN|ERR|ASSERT ]<msg>". Log level 'INFO' is used by
+                default if not specified.

drivers/platform/mellanox/mlxbf-bootctl.c

@@ -11,6 +11,7 @@
 #include <linux/acpi.h>
 #include <linux/arm-smccc.h>
 #include <linux/delay.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 
@@ -45,10 +46,39 @@ static const char * const mlxbf_bootctl_lifecycle_states[] = {
 	[3] = "RMA",
 };
 
+/* Log header format. */
+#define MLXBF_RSH_LOG_TYPE_MASK		GENMASK_ULL(59, 56)
+#define MLXBF_RSH_LOG_LEN_MASK		GENMASK_ULL(54, 48)
+#define MLXBF_RSH_LOG_LEVEL_MASK	GENMASK_ULL(7, 0)
+
+/* Log module ID and type (only MSG type in Linux driver for now). */
+#define MLXBF_RSH_LOG_TYPE_MSG		0x04ULL
+
+/* Log ctl/data register offset. */
+#define MLXBF_RSH_SCRATCH_BUF_CTL_OFF	0
+#define MLXBF_RSH_SCRATCH_BUF_DATA_OFF	0x10
+
+/* Log message levels. */
+enum {
+	MLXBF_RSH_LOG_INFO,
+	MLXBF_RSH_LOG_WARN,
+	MLXBF_RSH_LOG_ERR,
+	MLXBF_RSH_LOG_ASSERT
+};
+
 /* Mapped pointer for RSH_BOOT_FIFO_DATA and RSH_BOOT_FIFO_COUNT register. */
 static void __iomem *mlxbf_rsh_boot_data;
 static void __iomem *mlxbf_rsh_boot_cnt;
 
+/* Mapped pointer for rsh log semaphore/ctrl/data register. */
+static void __iomem *mlxbf_rsh_semaphore;
+static void __iomem *mlxbf_rsh_scratch_buf_ctl;
+static void __iomem *mlxbf_rsh_scratch_buf_data;
+
+/* Rsh log levels. */
+static const char * const mlxbf_rsh_log_level[] = {
+	"INFO", "WARN", "ERR", "ASSERT"};
+
 /* ARM SMC call which is atomic and no need for lock. */
 static int mlxbf_bootctl_smc(unsigned int smc_op, int smc_arg)
 {
@@ -266,12 +296,108 @@ static ssize_t fw_reset_store(struct device *dev,
 	return count;
 }
 
+/* Size(8-byte words) of the log buffer. */
+#define RSH_SCRATCH_BUF_CTL_IDX_MASK	0x7f
+
+/* 100ms timeout */
+#define RSH_SCRATCH_BUF_POLL_TIMEOUT	100000
+
+static int mlxbf_rsh_log_sem_lock(void)
+{
+	unsigned long reg;
+
+	return readq_poll_timeout(mlxbf_rsh_semaphore, reg, !reg, 0,
+				  RSH_SCRATCH_BUF_POLL_TIMEOUT);
+}
+
+static void mlxbf_rsh_log_sem_unlock(void)
+{
+	writeq(0, mlxbf_rsh_semaphore);
+}
+
+static ssize_t rsh_log_store(struct device *dev,
+			     struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	int rc, idx, num, len, level = MLXBF_RSH_LOG_INFO;
+	size_t size = count;
+	u64 data;
+
+	if (!size)
+		return -EINVAL;
+
+	if (!mlxbf_rsh_semaphore || !mlxbf_rsh_scratch_buf_ctl)
+		return -EOPNOTSUPP;
+
+	/* Ignore line break at the end. */
+	if (buf[size - 1] == '\n')
+		size--;
+
+	/* Check the message prefix. */
+	for (idx = 0; idx < ARRAY_SIZE(mlxbf_rsh_log_level); idx++) {
+		len = strlen(mlxbf_rsh_log_level[idx]);
+		if (len + 1 < size &&
+		    !strncmp(buf, mlxbf_rsh_log_level[idx], len)) {
+			buf += len;
+			size -= len;
+			level = idx;
+			break;
+		}
+	}
+
+	/* Ignore leading spaces. */
+	while (size > 0 && buf[0] == ' ') {
+		size--;
+		buf++;
+	}
+
+	/* Take the semaphore. */
+	rc = mlxbf_rsh_log_sem_lock();
+	if (rc)
+		return rc;
+
+	/* Calculate how many words are available. */
+	idx = readq(mlxbf_rsh_scratch_buf_ctl);
+	num = min((int)DIV_ROUND_UP(size, sizeof(u64)),
+		  RSH_SCRATCH_BUF_CTL_IDX_MASK - idx - 1);
+	if (num <= 0)
+		goto done;
+
+	/* Write Header. */
+	data = FIELD_PREP(MLXBF_RSH_LOG_TYPE_MASK, MLXBF_RSH_LOG_TYPE_MSG);
+	data |= FIELD_PREP(MLXBF_RSH_LOG_LEN_MASK, num);
+	data |= FIELD_PREP(MLXBF_RSH_LOG_LEVEL_MASK, level);
+	writeq(data, mlxbf_rsh_scratch_buf_data);
+
+	/* Write message. */
+	for (idx = 0; idx < num && size > 0; idx++) {
+		if (size < sizeof(u64)) {
+			data = 0;
+			memcpy(&data, buf, size);
+			size = 0;
+		} else {
+			memcpy(&data, buf, sizeof(u64));
+			size -= sizeof(u64);
+			buf += sizeof(u64);
+		}
+		writeq(data, mlxbf_rsh_scratch_buf_data);
+	}
+
+done:
+	/* Release the semaphore. */
+	mlxbf_rsh_log_sem_unlock();
+
+	/* Ignore the rest if no more space. */
+	return count;
+}
+
 static DEVICE_ATTR_RW(post_reset_wdog);
 static DEVICE_ATTR_RW(reset_action);
 static DEVICE_ATTR_RW(second_reset_action);
 static DEVICE_ATTR_RO(lifecycle_state);
 static DEVICE_ATTR_RO(secure_boot_fuse_state);
 static DEVICE_ATTR_WO(fw_reset);
+static DEVICE_ATTR_WO(rsh_log);
 
 static struct attribute *mlxbf_bootctl_attrs[] = {
 	&dev_attr_post_reset_wdog.attr,
@@ -280,6 +406,7 @@ static struct attribute *mlxbf_bootctl_attrs[] = {
 	&dev_attr_lifecycle_state.attr,
 	&dev_attr_secure_boot_fuse_state.attr,
 	&dev_attr_fw_reset.attr,
+	&dev_attr_rsh_log.attr,
 	NULL
 };
 
@@ -345,19 +472,32 @@ static bool mlxbf_bootctl_guid_match(const guid_t *guid,
 static int mlxbf_bootctl_probe(struct platform_device *pdev)
 {
 	struct arm_smccc_res res = { 0 };
+	void __iomem *reg;
 	guid_t guid;
 	int ret;
 
-	/* Get the resource of the bootfifo data register. */
+	/* Map the resource of the bootfifo data register. */
 	mlxbf_rsh_boot_data = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(mlxbf_rsh_boot_data))
 		return PTR_ERR(mlxbf_rsh_boot_data);
 
-	/* Get the resource of the bootfifo counter register. */
+	/* Map the resource of the bootfifo counter register. */
 	mlxbf_rsh_boot_cnt = devm_platform_ioremap_resource(pdev, 1);
 	if (IS_ERR(mlxbf_rsh_boot_cnt))
 		return PTR_ERR(mlxbf_rsh_boot_cnt);
 
+	/* Map the resource of the rshim semaphore register. */
+	mlxbf_rsh_semaphore = devm_platform_ioremap_resource(pdev, 2);
+	if (IS_ERR(mlxbf_rsh_semaphore))
+		return PTR_ERR(mlxbf_rsh_semaphore);
+
+	/* Map the resource of the scratch buffer (log) registers. */
+	reg = devm_platform_ioremap_resource(pdev, 3);
+	if (IS_ERR(reg))
+		return PTR_ERR(reg);
+	mlxbf_rsh_scratch_buf_ctl = reg + MLXBF_RSH_SCRATCH_BUF_CTL_OFF;
+	mlxbf_rsh_scratch_buf_data = reg + MLXBF_RSH_SCRATCH_BUF_DATA_OFF;
+
 	/* Ensure we have the UUID we expect for this service. */
 	arm_smccc_smc(MLXBF_BOOTCTL_SIP_SVC_UID, 0, 0, 0, 0, 0, 0, 0, &res);
 	guid_parse(mlxbf_bootctl_svc_uuid_str, &guid);