Date:	Mon, 26 May 2014 10:43:37 +0800
From:	<fwu@...vell.com>
To:	<linus.walleij@...aro.org>, <swarren@...dotorg.org>,
	<tony@...mide.com>
CC:	<linux-kernel@...r.kernel.org>, <swarren@...dia.com>,
	<fwu@...vell.com>, <cxie4@...vell.com>, <ylmao@...vell.com>,
	<njiang1@...vell.com>, <tianxf@...vell.com>, <fswu@...vell.com>
Subject: [PATCH v3] pinctrl: to avoid duplicated calling enable_pinmux_setting for a pin

From: Fan Wu <fwu@...vell.com>

What the patch did:
1.To call pinmux_disable_setting ahead of pinmux_enable_setting in each time of
  calling pinctrl_select_state
2.Remove the HW disable operation in in pinmux_disable_setting function.

The reason why to do this is that:
1.To avoid duplicated calling enable_setting operation without disabling
  operation which will let Pin's desc->mux_usecount keep being added.
2.The HW pin disable operation is not useful for most of the vendors' platform.
  And this can be used to avoid the HW glitch after using the item 1#
  modification.

In the following case, the issue can be reproduced:
1)There is a driver need to switch Pin state dynamicly, E.g. b/t "sleep" and
"default" state
2)The Pin setting configuration in DTS node may be like the following one:
component a {
	pinctrl-names = "default", "sleep";
	pinctrl-0 = <&a_grp_setting &c_grp_setting>;
	pinctrl-1 = <&b_grp_setting &c_grp_setting>;
}
The "c_grp_setting" config node is totaly same, maybe like following one:
c_grp_setting: c_grp_setting {
	pinctrl-single,pins = <GPIO48 AF6>;
	MFP_DEFAULT;
}
3)When switching the Pin state in the following official Pinctrl sequence:
	pin = pinctrl_get();
	state = pinctrl_lookup_state(wanted_state);
	pinctrl_select_state(state);
	pinctrl_put();

Test Result:
1)The switch is completed as expectation, that is: component's
Pins configuration are changed according to the description in the
"wanted_state" group setting
2)The "desc->mux_usecount" of corresponding Pins in "c_group" is added without being
decreased, because the "desc" is for each physical pin while the "setting" is
for each setting node in the DTS.
Thus, if the "c_grp_setting" in pinctrl-0 is not disabled ahead of enabling
"c_grp_setting" in pinctrl-1, the desc->mux_usecount will be kept added without
any chance to be decreased.

According to the comments in the original code, only the setting, in old state
but not in new state, will be "disable"(calling pinmux_disable_setting), which
is correct logic but not intact. We still need consider case that the setting
is in both old state and new state.
We can do this in the following two ways:
1) Avoid "enable"(calling pinmux_enable_setting) the Same Pins setting repeatedly.
2) "Disable"(calling pinmux_disable_setting) the "Same Pins setting", actually
two setting instance, ahead of enabling them.

Analysis:
1.The solution 2# is better because it can avoid too much iteration.
2.If we disable all of the setting in the old state and one/ones of the setting(s) is/are
existed in the new state, the Pin's mux function change may happen when
some SoC vendors defined the "pinctrl-single,function-off" in their DTS file.
old_setting=>disabled_setting=>new_setting.
3.In the pinmux framework, when Pin state is switched, the setting in the old state should be
marked as "disabled".

Conclusion:
1.To Remove the HW disabling operation to above the glitch mentioned above.
2.Handle the issue mentioned above by disabling all of the settings in old
state and then enable the all of the settings in new state.

Signed-off-by: Fan Wu <fwu@...vell.com>
Signed-off-by: Stephen Warren <swarren@...dia.com>
---
 drivers/pinctrl/core.c   |   24 +++++-------------------
 drivers/pinctrl/pinmux.c |    4 ----
 2 files changed, 5 insertions(+), 23 deletions(-)

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index c0fe609..4445a67 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -989,29 +989,15 @@ int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *state)
 
 	if (p->state) {
 		/*
-		 * The set of groups with a mux configuration in the old state
-		 * may not be identical to the set of groups with a mux setting
-		 * in the new state. While this might be unusual, it's entirely
-		 * possible for the "user"-supplied mapping table to be written
-		 * that way. For each group that was configured in the old state
-		 * but not in the new state, this code puts that group into a
-		 * safe/disabled state.
+		 * For each pinmux setting in the old state, forget SW's record
+		 * of mux owner for that pingroup. Any pingroups which are
+		 * still owned by the new state will be re-acquired by the call
+		 * to pinmux_enable_setting() in the loop below.
 		 */
 		list_for_each_entry(setting, &p->state->settings, node) {
-			bool found = false;
 			if (setting->type != PIN_MAP_TYPE_MUX_GROUP)
 				continue;
-			list_for_each_entry(setting2, &state->settings, node) {
-				if (setting2->type != PIN_MAP_TYPE_MUX_GROUP)
-					continue;
-				if (setting2->data.mux.group ==
-						setting->data.mux.group) {
-					found = true;
-					break;
-				}
-			}
-			if (!found)
-				pinmux_disable_setting(setting);
+			pinmux_disable_setting(setting);
 		}
 	}
 
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 9248ce4..c2c4aff 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -469,7 +469,6 @@ void pinmux_disable_setting(struct pinctrl_setting const *setting)
 {
 	struct pinctrl_dev *pctldev = setting->pctldev;
 	const struct pinctrl_ops *pctlops = pctldev->desc->pctlops;
-	const struct pinmux_ops *ops = pctldev->desc->pmxops;
 	int ret;
 	const unsigned *pins;
 	unsigned num_pins;
@@ -515,9 +514,6 @@ void pinmux_disable_setting(struct pinctrl_setting const *setting)
 				 pins[i], desc->name, gname);
 		}
 	}
-
-	if (ops->disable)
-		ops->disable(pctldev, setting->data.mux.func, setting->data.mux.group);
 }
 
 #ifdef CONFIG_DEBUG_FS
-- 
1.7.9.5

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