[v3,3/3] pinctrl: single: set pinmux from pins debug file

Message ID 20210520202730.4444-4-dariobin@libero.it
State New
Headers show
Series
  • am335x: set pinmux registers from pins debug file
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Commit Message

Dario Binacchi May 20, 2021, 8:27 p.m.
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>

---

Changes in v3:
- Remove CONFIG_DEV_MEM dependency.
- Change pcs_pin_dbg_set() interface (char *buf -> unsigned int val).

Changes in v2:
- Remove CONFIG_SOC_AM33XX dependency.

 drivers/pinctrl/pinctrl-single.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

Comments

Vladimir Zapolskiy May 21, 2021, 6:44 a.m. | #1
Hello Dario,

On 5/20/21 11:27 PM, Dario Binacchi wrote:
> 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:

this makes little sense, because it should be possible to write to the
registers without introduction of this interface, pin group/function
is the right level of abstraction for your particular task.

> 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>

I strongly object against this new interface to be added.

--
Best wishes,
Vladimir

Patch

diff --git a/drivers/pinctrl/pinctrl-single.c b/drivers/pinctrl/pinctrl-single.c
index 2c9c9835f375..1b75236563cf 100644
--- a/drivers/pinctrl/pinctrl-single.c
+++ b/drivers/pinctrl/pinctrl-single.c
@@ -313,6 +313,18 @@  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,
+			   unsigned int val)
+{
+	struct pcs_device *pcs;
+	unsigned int mux_bytes;
+
+	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 +343,7 @@  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,
+	.pin_dbg_set = pcs_pin_dbg_set,
 	.dt_node_to_map = pcs_dt_node_to_map,
 	.dt_free_map = pcs_dt_free_map,
 };