[PATCH v3] pinmux: allow exlusive pin allocation among GPIO and peripheral funtions via flag strict in struct pinctrl_desc

[Sonic Zhang <sonic.adi@gmail.com>]

From: Sonic Zhang <sonic.zhang@analog.com>

The blackfin pinmux and gpio controller doesn't allow user to set up 1 pin
for both GPIO and peripheral function. So, add flag strict in struct
pinctrl_desc to check both gpio_owner and mux_owner before approving the
pin request.

v2-changes:
- if strict flag is set, check gpio_owner and mux_onwer in if and else clause

v3-changes:
- add kerneldoc for this struct
- augment Documentation/pinctrl.txt

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
---
 Documentation/pinctrl.txt       |    7 +++++++
 drivers/pinctrl/pinctrl-adi2.c  |    1 +
 drivers/pinctrl/pinmux.c        |   13 +++++++++++++
 include/linux/pinctrl/pinctrl.h |    3 +++
 4 files changed, 24 insertions(+)

diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt
index 5e9909c..59e0aa7 100644
--- a/Documentation/pinctrl.txt
+++ b/Documentation/pinctrl.txt
@@ -850,6 +850,13 @@ possible that the GPIO, pin config and pin multiplex registers are placed into
 the same memory range and the same section of the data sheet, although that
 need not be the case.
 
+(B.1)
+In some processors, although the physical pins are designed in the same way
+as (B), the GPIO function still can't be enabled at the same time as the
+peripheral functions. So, a flag strict in struct pinctrl_desc is defined
+to check both gpio_owner and mux_owner before approving the pin request.
+Pinctrl driver should set this flag according to its hardware capability.
+
 From a kernel point of view, however, these are different aspects of the
 hardware and shall be put into different subsystems:
 
diff --git a/drivers/pinctrl/pinctrl-adi2.c b/drivers/pinctrl/pinctrl-adi2.c
index 8434439..fbd4926 100644
--- a/drivers/pinctrl/pinctrl-adi2.c
+++ b/drivers/pinctrl/pinctrl-adi2.c
@@ -710,6 +710,7 @@ static struct pinctrl_desc adi_pinmux_desc = {
 	.name = DRIVER_NAME,
 	.pctlops = &adi_pctrl_ops,
 	.pmxops = &adi_pinmux_ops,
+	.strict = true,
 	.owner = THIS_MODULE,
 };
 
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index b874458..2546fa7 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -107,6 +107,13 @@ static int pin_request(struct pinctrl_dev *pctldev,
 				desc->name, desc->gpio_owner, owner);
 			goto out;
 		}
+		if (pctldev->desc->strict && desc->mux_usecount &&
+		    strcmp(desc->mux_owner, owner)) {
+			dev_err(pctldev->dev,
+				"pin %s already requested by %s; cannot claim for %s\n",
+				desc->name, desc->mux_owner, owner);
+			goto out;
+		}
 
 		desc->gpio_owner = owner;
 	} else {
@@ -116,6 +123,12 @@ static int pin_request(struct pinctrl_dev *pctldev,
 				desc->name, desc->mux_owner, owner);
 			goto out;
 		}
+		if (pctldev->desc->strict && desc->gpio_owner) {
+			dev_err(pctldev->dev,
+				"pin %s already requested by %s; cannot claim for %s\n",
+				desc->name, desc->gpio_owner, owner);
+			goto out;
+		}
 
 		desc->mux_usecount++;
 		if (desc->mux_usecount > 1)
diff --git a/include/linux/pinctrl/pinctrl.h b/include/linux/pinctrl/pinctrl.h
index 66e4697..fc6b034 100644
--- a/include/linux/pinctrl/pinctrl.h
+++ b/include/linux/pinctrl/pinctrl.h
@@ -114,6 +114,8 @@ struct pinctrl_ops {
  *	of the pins field above
  * @pctlops: pin control operation vtable, to support global concepts like
  *	grouping of pins, this is optional.
+ * @strict: check both gpio_owner and mux_owner strictly before approving
+	the pin request
  * @pmxops: pinmux operations vtable, if you support pinmuxing in your driver
  * @confops: pin config operations vtable, if you support pin configuration in
  *	your driver
@@ -132,6 +134,7 @@ struct pinctrl_desc {
 	const struct pinctrl_ops *pctlops;
 	const struct pinmux_ops *pmxops;
 	const struct pinconf_ops *confops;
+	bool strict;
 	struct module *owner;
 #ifdef CONFIG_GENERIC_PINCONF
 	unsigned int num_custom_params;
-- 
1.7.9.5