[PATCH 0/2] am335x: set pinmux registers from pins debug file

[PATCH 0/2] 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



Dario Binacchi (2):
  pinctrl: core: configure pinmux from pins debug file
  pinctrl: single: set pinmux from pins debug file

 drivers/pinctrl/core.c           | 56 ++++++++++++++++++++++++++++++--
 drivers/pinctrl/pinctrl-single.c | 20 ++++++++++++
 include/linux/pinctrl/pinctrl.h  |  2 ++
 3 files changed, 76 insertions(+), 2 deletions(-)

-- 
2.17.1

[PATCH 2/2] pinctrl: single: set pinmux from pins debug file

[Dario Binacchi]

As described in section 9.1 of the TI reference manual for AM335x [1],
"For writing to the control module registers, the MPU will need to be in
privileged mode of operation and writes will not work from user mode".
By adding the pin_dbg_set helper to pcs_pinctrl_ops it will be possible
to write these registers from the pins debug:

cd /sys/kernel/debug/pinctrl/44e10800.pinmux-pinctrl-single/
echo <pin-number> <reg-value> >pins

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

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

---

 drivers/pinctrl/pinctrl-single.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/pinctrl/pinctrl-single.c b/drivers/pinctrl/pinctrl-single.c
index 2c9c9835f375..cdbc2298360d 100644
--- a/drivers/pinctrl/pinctrl-single.c
+++ b/drivers/pinctrl/pinctrl-single.c
@@ -313,6 +313,23 @@ static void pcs_pin_dbg_show(struct pinctrl_dev *pctldev,
 	seq_printf(s, "%zx %08x %s ", pa, val, DRIVER_NAME);
 }
 
+static int pcs_pin_dbg_set(struct pinctrl_dev *pctldev, unsigned int pin,
+			   char *buf)
+{
+	struct pcs_device *pcs;
+	unsigned int val, mux_bytes;
+
+	buf = skip_spaces(buf);
+	if (kstrtouint(buf, 0, &val))
+		return -EINVAL;
+
+	pcs = pinctrl_dev_get_drvdata(pctldev);
+
+	mux_bytes = pcs->width / BITS_PER_BYTE;
+	pcs->write(val, pcs->base + pin * mux_bytes);
+	return 0;
+}
+
 static void pcs_dt_free_map(struct pinctrl_dev *pctldev,
 				struct pinctrl_map *map, unsigned num_maps)
 {
@@ -331,6 +348,9 @@ static const struct pinctrl_ops pcs_pinctrl_ops = {
 	.get_group_name = pinctrl_generic_get_group_name,
 	.get_group_pins = pinctrl_generic_get_group_pins,
 	.pin_dbg_show = pcs_pin_dbg_show,
+#if IS_ENABLED(CONFIG_DEVMEM) && IS_ENABLED(CONFIG_SOC_AM33XX)
+	.pin_dbg_set = pcs_pin_dbg_set,
+#endif
 	.dt_node_to_map = pcs_dt_node_to_map,
 	.dt_free_map = pcs_dt_free_map,
 };
-- 
2.17.1

Re: [PATCH 2/2] pinctrl: single: set pinmux from pins debug file

[Tony Lindgren]

Hi,

* Dario Binacchi <dariobin@libero.it> [210516 13:55]:
> @@ -331,6 +348,9 @@ static const struct pinctrl_ops pcs_pinctrl_ops = {
>  	.get_group_name = pinctrl_generic_get_group_name,
>  	.get_group_pins = pinctrl_generic_get_group_pins,
>  	.pin_dbg_show = pcs_pin_dbg_show,
> +#if IS_ENABLED(CONFIG_DEVMEM) && IS_ENABLED(CONFIG_SOC_AM33XX)
> +	.pin_dbg_set = pcs_pin_dbg_set,
> +#endif
>  	.dt_node_to_map = pcs_dt_node_to_map,
>  	.dt_free_map = pcs_dt_free_map,
>  };

I don't think there should be any CONFIG_SOC_AM33XX dependency here?

Regards,

Tony