mlxbf-bootctl: Add sysfs file for BlueField boot fifo

This commit adds sysfs file for BlueField boot fifo. The boot
fifo is usually used to push boot stream via USB or PCIe. Once
OS is up, it can be reused by applications to read data or
configuration from external host.
Signed-off-by: Liming Sun <limings@nvidia.com>
Reviewed-by: David Thompson <davthompson@nvidia.com>
Link: https://lore.kernel.org/r/52b0b00dacbc4aad3169dd3667d79c85e334783b.1680657571.git.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

@@ -68,3 +68,10 @@ Description:
 		Wasted   burnt and invalid
 		Invalid  not burnt but marked as valid (error state).
 		=======  ===============================================
+
+What:		/sys/bus/platform/devices/MLNXBF04:00/bootfifo
+Date:		Apr 2023
+KernelVersion:	6.4
+Contact:	"Liming Sun <limings@nvidia.com>"
+Description:
+		The file used to access the BlueField boot fifo.

drivers/platform/mellanox/mlxbf-bootctl.c

@@ -10,6 +10,7 @@
 
 #include <linux/acpi.h>
 #include <linux/arm-smccc.h>
+#include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 
@@ -44,6 +45,10 @@ static const char * const mlxbf_bootctl_lifecycle_states[] = {
 	[3] = "RMA",
 };
 
+/* 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;
+
 /* ARM SMC call which is atomic and no need for lock. */
 static int mlxbf_bootctl_smc(unsigned int smc_op, int smc_arg)
 {
@@ -287,6 +292,45 @@ static const struct acpi_device_id mlxbf_bootctl_acpi_ids[] = {
 
 MODULE_DEVICE_TABLE(acpi, mlxbf_bootctl_acpi_ids);
 
+static ssize_t mlxbf_bootctl_bootfifo_read(struct file *filp,
+					   struct kobject *kobj,
+					   struct bin_attribute *bin_attr,
+					   char *buf, loff_t pos,
+					   size_t count)
+{
+	unsigned long timeout = msecs_to_jiffies(500);
+	unsigned long expire = jiffies + timeout;
+	u64 data, cnt = 0;
+	char *p = buf;
+
+	while (count >= sizeof(data)) {
+		/* Give up reading if no more data within 500ms. */
+		if (!cnt) {
+			cnt = readq(mlxbf_rsh_boot_cnt);
+			if (!cnt) {
+				if (time_after(jiffies, expire))
+					break;
+				usleep_range(10, 50);
+				continue;
+			}
+		}
+
+		data = readq(mlxbf_rsh_boot_data);
+		memcpy(p, &data, sizeof(data));
+		count -= sizeof(data);
+		p += sizeof(data);
+		cnt--;
+		expire = jiffies + timeout;
+	}
+
+	return p - buf;
+}
+
+static struct bin_attribute mlxbf_bootctl_bootfifo_sysfs_attr = {
+	.attr = { .name = "bootfifo", .mode = 0400 },
+	.read = mlxbf_bootctl_bootfifo_read,
+};
+
 static bool mlxbf_bootctl_guid_match(const guid_t *guid,
 				     const struct arm_smccc_res *res)
 {
@@ -304,6 +348,16 @@ static int mlxbf_bootctl_probe(struct platform_device *pdev)
 	guid_t guid;
 	int ret;
 
+	/* Get 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. */
+	mlxbf_rsh_boot_cnt = devm_platform_ioremap_resource(pdev, 1);
+	if (IS_ERR(mlxbf_rsh_boot_cnt))
+		return PTR_ERR(mlxbf_rsh_boot_cnt);
+
 	/* 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);
@@ -321,11 +375,25 @@ static int mlxbf_bootctl_probe(struct platform_device *pdev)
 	if (ret < 0)
 		dev_warn(&pdev->dev, "Unable to reset the EMMC boot mode\n");
 
+	ret = sysfs_create_bin_file(&pdev->dev.kobj,
+				    &mlxbf_bootctl_bootfifo_sysfs_attr);
+	if (ret)
+		pr_err("Unable to create bootfifo sysfs file, error %d\n", ret);
+
+	return ret;
+}
+
+static int mlxbf_bootctl_remove(struct platform_device *pdev)
+{
+	sysfs_remove_bin_file(&pdev->dev.kobj,
+			      &mlxbf_bootctl_bootfifo_sysfs_attr);
+
 	return 0;
 }
 
 static struct platform_driver mlxbf_bootctl_driver = {
 	.probe = mlxbf_bootctl_probe,
+	.remove = mlxbf_bootctl_remove,
 	.driver = {
 		.name = "mlxbf-bootctl",
 		.dev_groups = mlxbf_bootctl_groups,