[PATCH 1/2] pinctrl: imx: answer OUTPUT_ENABLE/INPUT_ENABLE queries from the pad register

[PATCH 1/2] pinctrl: imx: answer OUTPUT_ENABLE/INPUT_ENABLE queries from the pad register

[Mehmet Fide]

From: Mehmet Fide <mehmet.fide@screeningeagle.com>

The mmio pinconf get callback ignores which parameter was requested and
returns the raw conf register, so a generic query through
pinctrl_gpio_get_config() gets register bits back instead of the packed
parameter it asked for.

Decode the requested parameter and answer PIN_CONFIG_OUTPUT_ENABLE and
PIN_CONFIG_INPUT_ENABLE on SoCs that declare where those bits live in
the pad register; Vybrid has OBE at bit 1 and IBE at bit 0. The answer
is 0 with the bit value as the argument, which is what the
pinctrl_gpio_get_config() users (gpio-by-pinctrl, and gpio-mmio in the
next patch) expect. Pins the device tree never configured have no
register offset and get -ENOTSUPP, without the error message meant for
configuration attempts. Other parameters keep the historic raw-register
behaviour, which the debugfs dump still relies on.

This gives gpio-mmio a way to read back the line direction on chips
whose direction lives in the pin controller.

Suggested-by: Bartosz Golaszewski <brgl@kernel.org>
Signed-off-by: Mehmet Fide <mehmet.fide@screeningeagle.com>
---
 drivers/pinctrl/freescale/pinctrl-imx.c   | 30 +++++++++++++++++++++++
 drivers/pinctrl/freescale/pinctrl-imx.h   |  4 +++
 drivers/pinctrl/freescale/pinctrl-vf610.c |  2 ++
 3 files changed, 36 insertions(+)

diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c b/drivers/pinctrl/freescale/pinctrl-imx.c
index 9a45b376d36f..5da1a76b0141 100644
--- a/drivers/pinctrl/freescale/pinctrl-imx.c
+++ b/drivers/pinctrl/freescale/pinctrl-imx.c
@@ -21,6 +21,7 @@
 
 #include <linux/pinctrl/machine.h>
 #include <linux/pinctrl/pinconf.h>
+#include <linux/pinctrl/pinconf-generic.h>
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/pinctrl/pinmux.h>
 
@@ -297,6 +298,35 @@ static int imx_pinconf_get_mmio(struct pinctrl_dev *pctldev, unsigned pin_id,
 	struct imx_pinctrl *ipctl = pinctrl_dev_get_drvdata(pctldev);
 	const struct imx_pinctrl_soc_info *info = ipctl->info;
 	const struct imx_pin_reg *pin_reg = &ipctl->pin_regs[pin_id];
+	enum pin_config_param param = pinconf_to_config_param(*config);
+	unsigned int mask = 0;
+	u32 raw;
+
+	/*
+	 * Only OUTPUT_ENABLE/INPUT_ENABLE are decoded, and only when the SoC
+	 * declares the bits. Everything else still returns the raw conf
+	 * register, the debugfs dump depends on it.
+	 */
+	switch (param) {
+	case PIN_CONFIG_OUTPUT_ENABLE:
+		mask = info->obe_mask;
+		break;
+	case PIN_CONFIG_INPUT_ENABLE:
+		mask = info->ibe_mask;
+		break;
+	default:
+		break;
+	}
+
+	if (mask) {
+		/* pin not configured, nothing to report */
+		if (pin_reg->conf_reg == -1)
+			return -ENOTSUPP;
+
+		raw = readl(ipctl->base + pin_reg->conf_reg);
+		*config = pinconf_to_config_packed(param, !!(raw & mask));
+		return 0;
+	}
 
 	if (pin_reg->conf_reg == -1) {
 		dev_err(ipctl->dev, "Pin(%s) does not support config function\n",
diff --git a/drivers/pinctrl/freescale/pinctrl-imx.h b/drivers/pinctrl/freescale/pinctrl-imx.h
index f65ff45b4003..8fa7e1e2521d 100644
--- a/drivers/pinctrl/freescale/pinctrl-imx.h
+++ b/drivers/pinctrl/freescale/pinctrl-imx.h
@@ -91,6 +91,10 @@ struct imx_pinctrl_soc_info {
 	unsigned int mux_mask;
 	u8 mux_shift;
 
+	/* OBE/IBE bits in the conf register, 0 if the pad does not have them */
+	unsigned int obe_mask;
+	unsigned int ibe_mask;
+
 	int (*gpio_set_direction)(struct pinctrl_dev *pctldev,
 				  struct pinctrl_gpio_range *range,
 				  unsigned offset,
diff --git a/drivers/pinctrl/freescale/pinctrl-vf610.c b/drivers/pinctrl/freescale/pinctrl-vf610.c
index 76a4bc0181a0..77d077618782 100644
--- a/drivers/pinctrl/freescale/pinctrl-vf610.c
+++ b/drivers/pinctrl/freescale/pinctrl-vf610.c
@@ -319,6 +319,8 @@ static const struct imx_pinctrl_soc_info vf610_pinctrl_info = {
 	.gpio_set_direction = vf610_pmx_gpio_set_direction,
 	.mux_mask = 0x700000,
 	.mux_shift = 20,
+	.obe_mask = 0x2,
+	.ibe_mask = 0x1,
 };
 
 static const struct of_device_id vf610_pinctrl_of_match[] = {
-- 
2.54.0

Re: [PATCH 1/2] pinctrl: imx: answer OUTPUT_ENABLE/INPUT_ENABLE queries from the pad register

[Mehmet Fide]

From: Mehmet Fide <mehmet.fide@screeningeagle.com>

> [Severity: Medium]
> Is it safe to extract a parameter from the incoming *config pointer?
>
> Looking at imx_pinconf_group_dbg_show() in the same file, config is passed
> to imx_pinconf_get() uninitialized:
[...]
> This appears to permanently trap all subsequent loop iterations into falsely
> triggering the generic decoding path instead of returning raw registers.

Correct, the group dump reuses an uninitialized config across the loop
and my decode turns that into a sticky misread. In v2 the debugfs dumps
will read the raw register through their own helper, so they never go
through pin_config_get() and never depend on *config coming in.

> [Severity: High]
> This is a pre-existing issue, but does this correctly handle generic queries
> on SoCs that lack the requested masks?

Also correct. Once the dumps no longer use pin_config_get(), nothing
needs the raw fallback there anymore, so v2 makes the callback answer
only the parameters the SoC declares and return -ENOTSUPP for anything
else, instead of handing raw register bits to a generic caller.

Thanks,
Mehmet