Re: [PATCH 6/7] soundwire: debugfs: add interface to read/write commands

[Vinod Koul <vkoul@xxxxxxxxxx>]

On 26-03-24, 09:01, Bard Liao wrote:
> From: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> 
> 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

can we have a simpler interface? i am not a big fan of this kind of
structure for debugging.

How about two files read_bytes and write_bytes where you read/write
bytes.

echo 0x50 6 > read_bytes
cat read_bytes

in this format I would like to see addr and values (not need to print
address /value words (regmap does that too)

For write

echo start_addr N byte0 byte 1 ... byte N > write_bytes

 
> 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@xxxxxxxxxxxxxxx>
> Reviewed-by: Rander Wang <rander.wang@xxxxxxxxx>
> Signed-off-by: Bard Liao <yung-chuan.liao@xxxxxxxxxxxxxxx>
> ---
>  drivers/soundwire/debugfs.c | 150 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 150 insertions(+)
> 
> diff --git a/drivers/soundwire/debugfs.c b/drivers/soundwire/debugfs.c
> index 67abd7e52f09..6d253d69871d 100644
> --- a/drivers/soundwire/debugfs.c
> +++ b/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;
>  }
>  
> -- 
> 2.34.1

-- 
~Vinod