soundwire: debugfs: add interface to read/write commands

We have an existing debugfs files to read standard registers
(DP0/SCP/DPn).

This patch provides a more generic interface to ANY set of read/write
contiguous registers in a peripheral device. In follow-up patches,
this interface will be extended to use BRA transfers.

The sequence is to use the following files added under the existing
debugsfs directory for each peripheral device:

command (write 0, read 1)
num_bytes
start_address
firmware_file (only for writes)
read_buffer (only for reads)

Example for a read command - this checks the 6 bytes used for
enumeration.

cd /sys/kernel/debug/soundwire/master-0-0/sdw\:0\:025d\:0711\:01/
echo 1 > command
echo 6 > num_bytes
echo 0x50 > start_address
echo 1 > go
cat read_buffer
address 0x50 val 0x30
address 0x51 val 0x02
address 0x52 val 0x5d
address 0x53 val 0x07
address 0x54 val 0x11
address 0x55 val 0x01

Example with a 2-byte firmware file written in DP0 address 0x22

od -x /lib/firmware/test_firmware
0000000 0a37
0000002

cd /sys/kernel/debug/soundwire/master-0-0/sdw\:0\:025d\:0711\:01/
echo 0 > command
echo 2 > num_bytes
echo 0x22 > start_address
echo "test_firmware" > firmware_file
echo 1 > go

cd /sys/kernel/debug/soundwire/master-0-0/sdw\:0\:025d\:0711\:01/
echo 1 > command
echo 2 > num_bytes
echo 0x22 > start_address
echo 1 > go
cat read_buffer

address 0x22 val 0x37
address 0x23 val 0x0a

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20240603065841.4860-1-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/soundwire/debugfs.c

@@ -3,6 +3,7 @@
 
 #include <linux/device.h>
 #include <linux/debugfs.h>
+#include <linux/firmware.h>
 #include <linux/mod_devicetable.h>
 #include <linux/pm_runtime.h>
 #include <linux/slab.h>
@@ -137,6 +138,145 @@ static int sdw_slave_reg_show(struct seq_file *s_file, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(sdw_slave_reg);
 
+#define MAX_CMD_BYTES 256
+
+static int cmd;
+static u32 start_addr;
+static size_t num_bytes;
+static u8 read_buffer[MAX_CMD_BYTES];
+static char *firmware_file;
+
+static int set_command(void *data, u64 value)
+{
+	struct sdw_slave *slave = data;
+
+	if (value > 1)
+		return -EINVAL;
+
+	/* Userspace changed the hardware state behind the kernel's back */
+	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
+
+	dev_dbg(&slave->dev, "command: %s\n", value ? "read" : "write");
+	cmd = value;
+
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(set_command_fops, NULL,
+			 set_command, "%llu\n");
+
+static int set_start_address(void *data, u64 value)
+{
+	struct sdw_slave *slave = data;
+
+	/* Userspace changed the hardware state behind the kernel's back */
+	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
+
+	dev_dbg(&slave->dev, "start address %#llx\n", value);
+
+	start_addr = value;
+
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(set_start_address_fops, NULL,
+			 set_start_address, "%llu\n");
+
+static int set_num_bytes(void *data, u64 value)
+{
+	struct sdw_slave *slave = data;
+
+	if (value == 0 || value > MAX_CMD_BYTES)
+		return -EINVAL;
+
+	/* Userspace changed the hardware state behind the kernel's back */
+	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
+
+	dev_dbg(&slave->dev, "number of bytes %lld\n", value);
+
+	num_bytes = value;
+
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(set_num_bytes_fops, NULL,
+			 set_num_bytes, "%llu\n");
+
+static int cmd_go(void *data, u64 value)
+{
+	struct sdw_slave *slave = data;
+	int ret;
+
+	if (value != 1)
+		return -EINVAL;
+
+	/* one last check */
+	if (start_addr > SDW_REG_MAX ||
+	    num_bytes == 0 || num_bytes > MAX_CMD_BYTES)
+		return -EINVAL;
+
+	ret = pm_runtime_get_sync(&slave->dev);
+	if (ret < 0 && ret != -EACCES) {
+		pm_runtime_put_noidle(&slave->dev);
+		return ret;
+	}
+
+	/* Userspace changed the hardware state behind the kernel's back */
+	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
+
+	dev_dbg(&slave->dev, "starting command\n");
+
+	if (cmd == 0) {
+		const struct firmware *fw;
+
+		ret = request_firmware(&fw, firmware_file, &slave->dev);
+		if (ret < 0) {
+			dev_err(&slave->dev, "firmware %s not found\n", firmware_file);
+			goto out;
+		}
+
+		if (fw->size != num_bytes) {
+			dev_err(&slave->dev,
+				"firmware %s: unexpected size %zd, desired %zd\n",
+				firmware_file, fw->size, num_bytes);
+			release_firmware(fw);
+			goto out;
+		}
+
+		ret = sdw_nwrite_no_pm(slave, start_addr, num_bytes, fw->data);
+		release_firmware(fw);
+	} else {
+		ret = sdw_nread_no_pm(slave, start_addr, num_bytes, read_buffer);
+	}
+
+	dev_dbg(&slave->dev, "command completed %d\n", ret);
+
+out:
+	pm_runtime_mark_last_busy(&slave->dev);
+	pm_runtime_put(&slave->dev);
+
+	return ret;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(cmd_go_fops, NULL,
+			 cmd_go, "%llu\n");
+
+#define MAX_LINE_LEN 128
+
+static int read_buffer_show(struct seq_file *s_file, void *data)
+{
+	char buf[MAX_LINE_LEN];
+	int i;
+
+	if (num_bytes == 0 || num_bytes > MAX_CMD_BYTES)
+		return -EINVAL;
+
+	for (i = 0; i < num_bytes; i++) {
+		scnprintf(buf, MAX_LINE_LEN, "address %#x val 0x%02x\n",
+			  start_addr + i, read_buffer[i]);
+		seq_printf(s_file, "%s", buf);
+	}
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(read_buffer);
+
 void sdw_slave_debugfs_init(struct sdw_slave *slave)
 {
 	struct dentry *master;
@@ -151,6 +291,16 @@ void sdw_slave_debugfs_init(struct sdw_slave *slave)
 
 	debugfs_create_file("registers", 0400, d, slave, &sdw_slave_reg_fops);
 
+	/* interface to send arbitrary commands */
+	debugfs_create_file("command", 0200, d, slave, &set_command_fops);
+	debugfs_create_file("start_address", 0200, d, slave, &set_start_address_fops);
+	debugfs_create_file("num_bytes", 0200, d, slave, &set_num_bytes_fops);
+	debugfs_create_file("go", 0200, d, slave, &cmd_go_fops);
+
+	debugfs_create_file("read_buffer", 0400, d, slave, &read_buffer_fops);
+	firmware_file = NULL;
+	debugfs_create_str("firmware_file", 0200, d, &firmware_file);
+
 	slave->debugfs = d;
 }