linux-kernel - [PATCH v2 2/2] pinctrl: single: set pinmux from pins debug file

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Date:   Mon, 17 May 2021 22:00:02 +0200
From:   Dario Binacchi <dariobin@...ero.it>
To:     linux-kernel@...r.kernel.org
Cc:     Dario Binacchi <dariobin@...ero.it>,
        Haojian Zhuang <haojian.zhuang@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Tony Lindgren <tony@...mide.com>,
        linux-arm-kernel@...ts.infradead.org, linux-gpio@...r.kernel.org,
        linux-omap@...r.kernel.org
Subject: [PATCH v2 2/2] pinctrl: single: set pinmux from pins debug file

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@...ero.it>

---

Changes in v2:
- Remove CONFIG_SOC_AM33XX dependency.

 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..8497414e3384 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)
+	.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