[PATCH v3 0/3] am335x: set pinmux registers from pins debug file

[PATCH v3 0/3] am335x: set pinmux registers from pins debug file

[Dario Binacchi]

The patch was born from the need to change the slew rate of the LCD pins
of a custom AM335x board during EMC tests. The AM335x, as described in a
note in section 9.1 of its reference manual [1], is unable to write
pinmux registers from user space. The series now makes it possible to
write these registers from the pins debug file.

[1] https://www.ti.com/lit/ug/spruh73q/spruh73q.pdf


Changes in v3:
- Use strncpy_from_user() instead of copy_from_user().
- Do not shadow the error code returned by kstrtouint().
- Change pin_dbg_set() interface (char *buf --> unsigned int val).
- Describe pin_dbg_set().
- Remove CONFIG_DEV_MEM dependency.
- Change pcs_pin_dbg_set() interface (char *buf -> unsigned int val).

Changes in v2:
- Remove CONFIG_SOC_AM33XX dependency.

Dario Binacchi (3):
  docs/pinctrl: update `pins' description under debugfs
  pinctrl: core: configure pinmux from pins debug file
  pinctrl: single: set pinmux from pins debug file

 Documentation/driver-api/pin-control.rst |  3 ++
 drivers/pinctrl/core.c                   | 63 +++++++++++++++++++++++-
 drivers/pinctrl/pinctrl-single.c         | 13 +++++
 include/linux/pinctrl/pinctrl.h          |  4 ++
 4 files changed, 81 insertions(+), 2 deletions(-)

-- 
2.17.1

[PATCH v3 1/3] docs/pinctrl: update `pins' description under debugfs

[Dario Binacchi]

Optionally the `pins' file created inside the `/sys/kernel/debug/pinctrl'
subdirectory of each pin controller device now allows you to set the
mux register of a pin.

Signed-off-by: Dario Binacchi <dariobin@libero.it>
---

(no changes since v1)

 Documentation/driver-api/pin-control.rst | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst
index e2474425fb0c..3d8192fa45a3 100644
--- a/Documentation/driver-api/pin-control.rst
+++ b/Documentation/driver-api/pin-control.rst
@@ -1447,6 +1447,9 @@ 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.
+  Optionally writes the mux register for the selected pin.
+  e.g. to write the value 0x73 in the mux register of pin 19:
+  echo 19 0x73 >/sys/kernel/debug/pinctrl/pins
 
 - ``gpio-ranges``: print ranges that map gpio lines to pins on the controller
 
-- 
2.17.1

Re: [PATCH v3 0/3] am335x: set pinmux registers from pins debug file

[Linus Walleij]

On Thu, May 20, 2021 at 10:27 PM Dario Binacchi <dariobin@libero.it> wrote:

> The patch was born from the need to change the slew rate of the LCD pins
> of a custom AM335x board during EMC tests. The AM335x, as described in a
> note in section 9.1 of its reference manual [1], is unable to write
> pinmux registers from user space. The series now makes it possible to
> write these registers from the pins debug file.

I am going to hold this series back pending more discussion on the ABI
and whether it is useful.

Yours,
Linus Walleij