[PATCH v7 0/3] pinctrl: pinmux: Add pinmux-select debugfs file

[PATCH v7 0/3] pinctrl: pinmux: Add pinmux-select debugfs file

[Drew Fustini]

This series first converts the debugfs files in the pinctrl subsystem to
octal permissions and then adds a new debugfs file "pinmux-select".

Function name and group name can be written to "pinmux-select" which
will cause the function and group to be activated on the pin controller.

The final patch in this series documents the debugfs files for pinctrl.

Notes for PATCH v7:
- add 'Reviewed-by:' from Andy Shevchenko for pinmux-select patch
- add 'Reviewed-by:' from Andy Shevchenko for documentation patch
- add 'Reviewed-by:' from Tony Lindgren to all patches
- change order of '#include <linux/ctype.h>' per Andy's suggestion
- change PINMUX_SELECT_MAX back to 128 as I had accidentally changed it
  to 50 and Andy pointed this out.
- grammer fixes as suggested by Andy
- rework assignment of fsel and ret from pinmux_func_name_to_selector()
- rework assignment of gsel and ret from pinctrl_get_group_selector()

Notes for PATCH v6:
- add 'Suggested-by:' for Joe Perches to octal permissions patch
- add 'Reviewed-by:' from Andy and Geert to octal permissions patch
- reword example in the pinmux-select patch per Andy's advice
- indent the example output per Andy's advice
- remove usage error messages as Andy advised it is too verbose
- return -ENOMEM when write is too big for the input buffer per Andy's advice
- handle whitespace before, in between, and after the function name and
  group name as suggested by Andy
- rename free_buf to exit_free_buf per Andy's advice
- add documentation patch to series which documents the debugfs files
  for the pinctrl subsystem including the new pinmux-select file

Notes for PATCH v5:
- convert permissions from symbolic to octal for debugfs_create_file()
  calls in core.c that Joe Perches pointed out I had missed
- Linus W: please let me know if I should break this series apart as you
  already applied an earlier version of octal conversion patch today [1]
- switch from sscanf() to just pointing to function name and group name
  inside of the buffer. This also avoids having to allocate additional
  buffers for fname and gname. Geert and Andy highlighted this security
  issue and Andy suggested code to use instead of sscanf().
- switch from devm_kfree() to kfree() after Dan Carpenter warned me
- remove .read from pinmux_select_ops per Geert since it is write only
- add usage format to error when unable find fname or gname in buffer

Notes for PATCH v4:
- correct the commit message in the second patch to reference function
  and group name instead of integer selectors. Apologies for not fixing
  that in v3
- fix typos in cover letter

Notes for PATCH v3:
- add Suggested-by: Andy Shevchenko to the "pinctrl: use to octal
  permissions for debugfs files" patch
- change the octal permissions from 0400 to 0444 to correctly match the
  symbolic permissions (thanks to Joe Perches and Geert Uytterhoeven)
- note that S_IFREG flag is added to the mode in __debugfs_create_file()
  (thanks to Andy for highlighting this and Joe for suggesting I should
  add a note to the commit message)
- fix order of the goto labels so that the buffers are freed correctly
  as suggested by Dan Carpenter
- move from devm_kzalloc() to kzalloc() as the buffers are only used
  inside the pinmux_select() function and not related to the lifetime
  of the pin controller device (thanks to Andy for pointing this out)
- correct the pinmux-select example in commit message to use the
  function and group name instead of selector (thanks to Geert)

Notes for PATCH v2:
- create patch series that includes patch to switch all the debugfs
  files in pinctrl subsystem over to octal permission
- write function name and group name, instead of error-prone selector
  numbers, to the 'pinmux-select' file
- switch from static to dynamic allocation for the kernel buffer filled
  by strncpy_from_user()
- look up function selector from function name using
  pinmux_func_name_to_selector()
- validate group name with get_function_groups() and match_string()
- look up selector for group name with pinctrl_get_group_selector()

Notes for PATCH v1:
- posted seperate patch to switch all the debugfs files in pinctrl
  subsystem over to octal permission
- there is no existing documentation for any of the debugfs enteries for
  pinctrl, so it seemed to have a bigger scope than just this patch. I
  also noticed that rst documentation is confusingly named "pinctl" (no
  'r') and started thread about that [2]. Linus suggested chaning that
  to 'pin-control'. Thus I am planning a seperate documentation patch
  series where the file is renamed, references changed and a section on
  the pinctrl debugfs files is added.

Notes for RFC v2 [3]:
- rename debugfs file "pinmux-set" to "pinmux-select"
- renmae pinmux_set_write() to pinmux_select()
- switch from memdup_user_nul() to strncpy_from_user()
- switch from pr_warn() to dev_err()

[1] https://lore.kernel.org/linux-gpio/20210126044742.87602-1-drew@beagleboard.org/
[2] https://lore.kernel.org/linux-gpio/20210126050817.GA187797@x1/
[3] https://lore.kernel.org/linux-gpio/20210123064909.466225-1-drew@beagleboard.org/

Drew Fustini (3):
  pinctrl: use to octal permissions for debugfs files
  pinctrl: pinmux: Add pinmux-select debugfs file
  docs/pinctrl: document debugfs files

 Documentation/driver-api/pinctl.rst |  37 ++++++++++
 drivers/pinctrl/core.c              |  12 ++--
 drivers/pinctrl/pinconf.c           |   4 +-
 drivers/pinctrl/pinmux.c            | 106 +++++++++++++++++++++++++++-
 4 files changed, 149 insertions(+), 10 deletions(-)

-- 
2.25.1

[PATCH v7 1/3] pinctrl: use to octal permissions for debugfs files

[Drew Fustini]

Switch over pinctrl debugfs files to use octal permissions as they are
preferred over symbolic permissions. Refer to commit f90774e1fd27
("checkpatch: look for symbolic permissions and suggest octal instead").

Note: S_IFREG flag is added to the mode by __debugfs_create_file()
in fs/debugfs/inode.c

Suggested-by: Joe Perches <joe@perches.com>
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Drew Fustini <drew@beagleboard.org>
---
 drivers/pinctrl/core.c    | 12 ++++++------
 drivers/pinctrl/pinconf.c |  4 ++--
 drivers/pinctrl/pinmux.c  |  4 ++--
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index 3663d87f51a0..07458742bc0f 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -1888,11 +1888,11 @@ static void pinctrl_init_device_debugfs(struct pinctrl_dev *pctldev)
 			dev_name(pctldev->dev));
 		return;
 	}
-	debugfs_create_file("pins", S_IFREG | S_IRUGO,
+	debugfs_create_file("pins", 0444,
 			    device_root, pctldev, &pinctrl_pins_fops);
-	debugfs_create_file("pingroups", S_IFREG | S_IRUGO,
+	debugfs_create_file("pingroups", 0444,
 			    device_root, pctldev, &pinctrl_groups_fops);
-	debugfs_create_file("gpio-ranges", S_IFREG | S_IRUGO,
+	debugfs_create_file("gpio-ranges", 0444,
 			    device_root, pctldev, &pinctrl_gpioranges_fops);
 	if (pctldev->desc->pmxops)
 		pinmux_init_device_debugfs(device_root, pctldev);
@@ -1914,11 +1914,11 @@ static void pinctrl_init_debugfs(void)
 		return;
 	}
 
-	debugfs_create_file("pinctrl-devices", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinctrl-devices", 0444,
 			    debugfs_root, NULL, &pinctrl_devices_fops);
-	debugfs_create_file("pinctrl-maps", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinctrl-maps", 0444,
 			    debugfs_root, NULL, &pinctrl_maps_fops);
-	debugfs_create_file("pinctrl-handles", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinctrl-handles", 0444,
 			    debugfs_root, NULL, &pinctrl_fops);
 }
 
diff --git a/drivers/pinctrl/pinconf.c b/drivers/pinctrl/pinconf.c
index 02c075cc010b..d9d54065472e 100644
--- a/drivers/pinctrl/pinconf.c
+++ b/drivers/pinctrl/pinconf.c
@@ -370,9 +370,9 @@ DEFINE_SHOW_ATTRIBUTE(pinconf_groups);
 void pinconf_init_device_debugfs(struct dentry *devroot,
 			 struct pinctrl_dev *pctldev)
 {
-	debugfs_create_file("pinconf-pins", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinconf-pins", 0444,
 			    devroot, pctldev, &pinconf_pins_fops);
-	debugfs_create_file("pinconf-groups", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinconf-groups", 0444,
 			    devroot, pctldev, &pinconf_groups_fops);
 }
 
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index bab888fe3f8e..c651b2db0925 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -676,9 +676,9 @@ DEFINE_SHOW_ATTRIBUTE(pinmux_pins);
 void pinmux_init_device_debugfs(struct dentry *devroot,
 			 struct pinctrl_dev *pctldev)
 {
-	debugfs_create_file("pinmux-functions", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinmux-functions", 0444,
 			    devroot, pctldev, &pinmux_functions_fops);
-	debugfs_create_file("pinmux-pins", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinmux-pins", 0444,
 			    devroot, pctldev, &pinmux_pins_fops);
 }
 
-- 
2.25.1

[PATCH v7 2/3] pinctrl: pinmux: Add pinmux-select debugfs file

[Drew Fustini]

Add "pinmux-select" to debugfs which will activate a function and group:

  echo "<function-name group-name>" > pinmux-select

The write operation pinmux_select() handles this by checking that the
names map to valid selectors and then calling ops->set_mux().

The existing "pinmux-functions" debugfs file lists the pin functions
registered for the pin controller. For example:

  function: pinmux-uart0, groups = [ pinmux-uart0-pins ]
  function: pinmux-mmc0, groups = [ pinmux-mmc0-pins ]
  function: pinmux-mmc1, groups = [ pinmux-mmc1-pins ]
  function: pinmux-i2c0, groups = [ pinmux-i2c0-pins ]
  function: pinmux-i2c1, groups = [ pinmux-i2c1-pins ]
  function: pinmux-spi1, groups = [ pinmux-spi1-pins ]

To activate function pinmux-i2c1 and group pinmux-i2c1-pins:

  echo "pinmux-i2c1 pinmux-i2c1-pins" > pinmux-select

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Drew Fustini <drew@beagleboard.org>
---
 drivers/pinctrl/pinmux.c | 102 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index c651b2db0925..39770af56562 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -12,6 +12,7 @@
  */
 #define pr_fmt(fmt) "pinmux core: " fmt
 
+#include <linux/ctype.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
@@ -673,6 +674,105 @@ void pinmux_show_setting(struct seq_file *s,
 DEFINE_SHOW_ATTRIBUTE(pinmux_functions);
 DEFINE_SHOW_ATTRIBUTE(pinmux_pins);
 
+#define PINMUX_SELECT_MAX 50
+static ssize_t pinmux_select(struct file *file, const char __user *user_buf,
+				   size_t len, loff_t *ppos)
+{
+	struct seq_file *sfile = file->private_data;
+	struct pinctrl_dev *pctldev = sfile->private;
+	const struct pinmux_ops *pmxops = pctldev->desc->pmxops;
+	const char *const *groups;
+	char *buf, *fname, *gname;
+	unsigned int num_groups;
+	int fsel, gsel, ret;
+
+	if (len > PINMUX_SELECT_MAX)
+		return -ENOMEM;
+
+	buf = kzalloc(PINMUX_SELECT_MAX, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = strncpy_from_user(buf, user_buf, PINMUX_SELECT_MAX);
+	if (ret < 0)
+		goto exit_free_buf;
+	buf[len-1] = '\0';
+
+	/* remove leading and trailing spaces of input buffer */
+	fname = strstrip(buf);
+	if (*fname == '\0') {
+		ret = -EINVAL;
+		goto exit_free_buf;
+	}
+
+	/* find a separator which is a spacelike character */
+	for (gname = fname; !isspace(*gname); gname++) {
+		if (*gname == '\0') {
+			ret = -EINVAL;
+			goto exit_free_buf;
+		}
+	}
+	*gname = '\0';
+
+	/* drop extra spaces between function and group names */
+	gname = skip_spaces(gname + 1);
+	if (*gname == '\0') {
+		ret = -EINVAL;
+		goto exit_free_buf;
+	}
+
+	ret = pinmux_func_name_to_selector(pctldev, fname);
+	if (ret < 0) {
+		dev_err(pctldev->dev, "invalid function %s in map table\n", fname);
+		goto exit_free_buf;
+	}
+	fsel = ret;
+
+	ret = pmxops->get_function_groups(pctldev, fsel, &groups, &num_groups);
+	if (ret) {
+		dev_err(pctldev->dev, "no groups for function %d (%s)", fsel, fname);
+		goto exit_free_buf;
+	}
+
+	ret = match_string(groups, num_groups, gname);
+	if (ret < 0) {
+		dev_err(pctldev->dev, "invalid group %s", gname);
+		goto exit_free_buf;
+	}
+
+	ret = pinctrl_get_group_selector(pctldev, gname);
+	if (ret < 0) {
+		dev_err(pctldev->dev, "failed to get group selector for %s", gname);
+		goto exit_free_buf;
+	}
+	gsel = ret;
+
+	ret = pmxops->set_mux(pctldev, fsel, gsel);
+	if (ret) {
+		dev_err(pctldev->dev, "set_mux() failed: %d", ret);
+		goto exit_free_buf;
+	}
+	ret = len;
+
+exit_free_buf:
+	kfree(buf);
+
+	return ret;
+}
+
+static int pinmux_select_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, NULL, inode->i_private);
+}
+
+static const struct file_operations pinmux_select_ops = {
+	.owner = THIS_MODULE,
+	.open = pinmux_select_open,
+	.write = pinmux_select,
+	.llseek = no_llseek,
+	.release = single_release,
+};
+
 void pinmux_init_device_debugfs(struct dentry *devroot,
 			 struct pinctrl_dev *pctldev)
 {
@@ -680,6 +780,8 @@ void pinmux_init_device_debugfs(struct dentry *devroot,
 			    devroot, pctldev, &pinmux_functions_fops);
 	debugfs_create_file("pinmux-pins", 0444,
 			    devroot, pctldev, &pinmux_pins_fops);
+	debugfs_create_file("pinmux-select", 0200,
+			    devroot, pctldev, &pinmux_select_ops);
 }
 
 #endif /* CONFIG_DEBUG_FS */
-- 
2.25.1

[PATCH v7 3/3] docs/pinctrl: document debugfs files

[Drew Fustini]

Document debugfs directories and files created for pinctrl subsystem.

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Drew Fustini <drew@beagleboard.org>
---
 Documentation/driver-api/pinctl.rst | 37 +++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/Documentation/driver-api/pinctl.rst b/Documentation/driver-api/pinctl.rst
index 3d2deaf48841..37bc3bd64cd8 100644
--- a/Documentation/driver-api/pinctl.rst
+++ b/Documentation/driver-api/pinctl.rst
@@ -1428,3 +1428,40 @@ on the pins defined by group B::
 The above has to be done from process context. The reservation of the pins
 will be done when the state is activated, so in effect one specific pin
 can be used by different functions at different times on a running system.
+
+
+Debugfs files
+=============
+These files are created in ``/sys/kernel/debug/pinctrl``:
+
+- ``pinctrl-devices``: prints each pin controller device along with columns to
+  indicate support for pinmux and pinconf
+
+- ``pinctrl-handles``: iterate through the list of pin controller handles and
+  print the corresponding pinmux maps
+
+- ``pinctrl-maps``: print all pinctrl maps
+
+A sub-directory is created inside of ``/sys/kernel/debug/pinctrl`` for each pin
+controller device containing these files:
+
+- ``pins``: prints a line for each pin registered on the pin controller. The
+  pinctrl driver may add additional information such as register contents.
+
+- ``gpio-ranges``: print ranges that map gpio lines to pins on the controller
+
+- ``pingroups``: print all pin groups registered on the pin controller
+
+- ``pinconf-pins``: print pin config settings for each pin
+
+- ``pinconf-groups``: print pin config settings per pin group
+
+- ``pinmux-functions``: print each pin function along with the pin groups that
+  map to the pin function
+
+- ``pinmux-pins``: iterate through all pins and print mux owner, gpio owner
+  and if the pin is a hog
+
+- ``pinmux-select``: write to this file to activate a pin function and group::
+
+        echo "<function-name group-name>" > pinmux-select
-- 
2.25.1

Re: [PATCH v7 2/3] pinctrl: pinmux: Add pinmux-select debugfs file

[Geert Uytterhoeven]

Hi Drew,

On Wed, Feb 17, 2021 at 11:15 PM Drew Fustini <drew@beagleboard.org> wrote:
> Add "pinmux-select" to debugfs which will activate a function and group:
>
>   echo "<function-name group-name>" > pinmux-select
>
> The write operation pinmux_select() handles this by checking that the
> names map to valid selectors and then calling ops->set_mux().
>
> The existing "pinmux-functions" debugfs file lists the pin functions
> registered for the pin controller. For example:
>
>   function: pinmux-uart0, groups = [ pinmux-uart0-pins ]
>   function: pinmux-mmc0, groups = [ pinmux-mmc0-pins ]
>   function: pinmux-mmc1, groups = [ pinmux-mmc1-pins ]
>   function: pinmux-i2c0, groups = [ pinmux-i2c0-pins ]
>   function: pinmux-i2c1, groups = [ pinmux-i2c1-pins ]
>   function: pinmux-spi1, groups = [ pinmux-spi1-pins ]
>
> To activate function pinmux-i2c1 and group pinmux-i2c1-pins:
>
>   echo "pinmux-i2c1 pinmux-i2c1-pins" > pinmux-select
>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Reviewed-by: Tony Lindgren <tony@atomide.com>
> Signed-off-by: Drew Fustini <drew@beagleboard.org>

Thanks for your patch!

On R-Car M2-W, which does not use pinctrl-single, I have:

    # cat pinmux-functions
    ...
    function 14: i2c2, groups = [ i2c2 i2c2_b i2c2_c i2c2_d ]
    ...
    function 51: ssi, groups = [ ssi0_data ssi0_data_b ssi0129_ctrl
ssi0129_ctrl_b ssi1_data ssi1_data_b ssi1_ctrl ssi1_ctrl_b ssi2_data
ssi2_ctrl ssi3_data ssi34_ctrl ssi4_data ssi4_ctrl ssi5_data ssi5_ctrl
ssi6_data ssi6_ctrl ssi7_data ssi7_data_b ssi78_ctrl ssi78_ctrl_b
ssi8_data ssi8_data_b ssi9_data ssi9_data_b ssi9_ctrl ssi9_ctrl_b ]
    ...

On the Koelsch board:

    # cd /sys/kernel/debug/pinctrl/e6060000.pinctrl-sh-pfc/
    # echo ssi ssi2_ctrl > pinmux-select # Configure i2c2 pins for ssi
    # i2cdetect -y -a 2                  # Fails
    # echo i2c2 i2c2 > pinmux-select     # Restore i2c2
    # i2cdetect -y -a 2                  # Works again

The order of the 2 parameters looks a bit odd to me, as the operation
configures the pins from "group" to be used for "function".
See also arch/arm/boot/dts/r8a7791-koelsch.dts
For the i2c2 example it's not that obvious, but for ssi it is.
Might feel different for pinctrl-single, and perhaps I just need to get
used to it ;-)

Anyway:
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v7 3/3] docs/pinctrl: document debugfs files

[Geert Uytterhoeven]

Hi Drew,

On Wed, Feb 17, 2021 at 11:15 PM Drew Fustini <drew@beagleboard.org> wrote:
> Document debugfs directories and files created for pinctrl subsystem.
>
> Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Reviewed-by: Tony Lindgren <tony@atomide.com>
> Signed-off-by: Drew Fustini <drew@beagleboard.org>

Thanks for your patch!

> --- a/Documentation/driver-api/pinctl.rst
> +++ b/Documentation/driver-api/pinctl.rst
> @@ -1428,3 +1428,40 @@ on the pins defined by group B::
>  The above has to be done from process context. The reservation of the pins
>  will be done when the state is activated, so in effect one specific pin
>  can be used by different functions at different times on a running system.
> +
> +
> +Debugfs files
> +=============
> +These files are created in ``/sys/kernel/debug/pinctrl``:
> +
> +- ``pinctrl-devices``: prints each pin controller device along with columns to
> +  indicate support for pinmux and pinconf
> +
> +- ``pinctrl-handles``: iterate through the list of pin controller handles and
> +  print the corresponding pinmux maps

Do you need the iterate part?

"prints each configured pin controller handle and the corresponding
 pinmux maps"?

> +
> +- ``pinctrl-maps``: print all pinctrl maps
> +
> +A sub-directory is created inside of ``/sys/kernel/debug/pinctrl`` for each pin
> +controller device containing these files:

Sort the below alphabetically?

> +
> +- ``pins``: prints a line for each pin registered on the pin controller. The
> +  pinctrl driver may add additional information such as register contents.
> +
> +- ``gpio-ranges``: print ranges that map gpio lines to pins on the controller
> +
> +- ``pingroups``: print all pin groups registered on the pin controller
> +
> +- ``pinconf-pins``: print pin config settings for each pin
> +
> +- ``pinconf-groups``: print pin config settings per pin group
> +
> +- ``pinmux-functions``: print each pin function along with the pin groups that
> +  map to the pin function
> +
> +- ``pinmux-pins``: iterate through all pins and print mux owner, gpio owner
> +  and if the pin is a hog
> +
> +- ``pinmux-select``: write to this file to activate a pin function and group::

a pin function for a group?

> +
> +        echo "<function-name group-name>" > pinmux-select

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v7 2/3] pinctrl: pinmux: Add pinmux-select debugfs file

[Drew Fustini]

On Fri, Feb 19, 2021 at 10:06:51AM +0100, Geert Uytterhoeven wrote:
> Hi Drew,
> 
> On Wed, Feb 17, 2021 at 11:15 PM Drew Fustini <drew@beagleboard.org> wrote:
> > Add "pinmux-select" to debugfs which will activate a function and group:
> >
> >   echo "<function-name group-name>" > pinmux-select
> >
> > The write operation pinmux_select() handles this by checking that the
> > names map to valid selectors and then calling ops->set_mux().
> >
> > The existing "pinmux-functions" debugfs file lists the pin functions
> > registered for the pin controller. For example:
> >
> >   function: pinmux-uart0, groups = [ pinmux-uart0-pins ]
> >   function: pinmux-mmc0, groups = [ pinmux-mmc0-pins ]
> >   function: pinmux-mmc1, groups = [ pinmux-mmc1-pins ]
> >   function: pinmux-i2c0, groups = [ pinmux-i2c0-pins ]
> >   function: pinmux-i2c1, groups = [ pinmux-i2c1-pins ]
> >   function: pinmux-spi1, groups = [ pinmux-spi1-pins ]
> >
> > To activate function pinmux-i2c1 and group pinmux-i2c1-pins:
> >
> >   echo "pinmux-i2c1 pinmux-i2c1-pins" > pinmux-select
> >
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> > Reviewed-by: Tony Lindgren <tony@atomide.com>
> > Signed-off-by: Drew Fustini <drew@beagleboard.org>
> 
> Thanks for your patch!
> 
> On R-Car M2-W, which does not use pinctrl-single, I have:
> 
>     # cat pinmux-functions
>     ...
>     function 14: i2c2, groups = [ i2c2 i2c2_b i2c2_c i2c2_d ]
>     ...
>     function 51: ssi, groups = [ ssi0_data ssi0_data_b ssi0129_ctrl
> ssi0129_ctrl_b ssi1_data ssi1_data_b ssi1_ctrl ssi1_ctrl_b ssi2_data
> ssi2_ctrl ssi3_data ssi34_ctrl ssi4_data ssi4_ctrl ssi5_data ssi5_ctrl
> ssi6_data ssi6_ctrl ssi7_data ssi7_data_b ssi78_ctrl ssi78_ctrl_b
> ssi8_data ssi8_data_b ssi9_data ssi9_data_b ssi9_ctrl ssi9_ctrl_b ]
>     ...
> 
> On the Koelsch board:
> 
>     # cd /sys/kernel/debug/pinctrl/e6060000.pinctrl-sh-pfc/
>     # echo ssi ssi2_ctrl > pinmux-select # Configure i2c2 pins for ssi
>     # i2cdetect -y -a 2                  # Fails
>     # echo i2c2 i2c2 > pinmux-select     # Restore i2c2
>     # i2cdetect -y -a 2                  # Works again
> 
> The order of the 2 parameters looks a bit odd to me, as the operation
> configures the pins from "group" to be used for "function".
> See also arch/arm/boot/dts/r8a7791-koelsch.dts
> For the i2c2 example it's not that obvious, but for ssi it is.
> Might feel different for pinctrl-single, and perhaps I just need to get
> used to it ;-)

Thank you for comments and testing.

Regarding the order of "<function-name> <group-name>", I can change it
to "<group-name function-name>" if that seems more natural.

pinctrl-single does not actually use the group selector in pcs_set_mux()
so it essentially does not matter for pinctrl-single.

-Drew

> 
> Anyway:
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds