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authorFan Wu <fwu@marvell.com>2014-06-09 05:37:56 +0400
committerLinus Walleij <linus.walleij@linaro.org>2014-07-11 16:08:26 +0400
commit2243a87d90b42eb38bc281957df3e57c712b5e56 (patch)
tree8083e8a008c65b667de08e2603032e80516f4ecb /drivers/pinctrl/vt8500
parent607af165c0470e7297e1a04f528176222849b5a9 (diff)
downloadlinux-2243a87d90b42eb38bc281957df3e57c712b5e56.tar.xz
pinctrl: avoid duplicated calling enable_pinmux_setting for a pin
What the patch does: 1. Call pinmux_disable_setting ahead of pinmux_enable_setting each time pinctrl_select_state is called 2. Remove the HW disable operation in pinmux_disable_setting function. 3. Remove the disable ops in struct pinmux_ops 4. Remove all the disable ops users in current code base. Notes: 1. Great thanks for the suggestion from Linus, Tony Lindgren and Stephen Warren and Everyone that shared comments on this patch. 2. The patch also includes comment fixes from Stephen Warren. The reason why we do this: 1. To avoid duplicated calling of the enable_setting operation without disabling operation inbetween which will let the pin descriptor desc->mux_usecount increase monotonously. 2. The HW pin disable operation is not useful for any of the existing platforms. 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 that need to switch pin state dynamically, e.g. between "sleep" and "default" state 2. The pin setting configuration in a DTS node may be like this: 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 totally identical, maybe like following one: c_grp_setting: c_grp_setting { pinctrl-single,pins = <GPIO48 AF6>; } 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 expected, that is: the device's pin configuration is changed according to the description in the "wanted_state" group setting 2. The "desc->mux_usecount" of the corresponding pins in "c_group" is increased 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 keep increasing 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 "disabled" (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 to "enable"(calling pinmux_enable_setting) the "same pin setting" repeatedly 2. "Disable"(calling pinmux_disable_setting) the "same pin setting", actually two setting instances, 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 settings in the old state and one of the setting(s) exist in the new state, the pins 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 a 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@marvell.com> Acked-by: Stephen Warren <swarren@nvidia.com> Acked-by: Patrice Chotard <patrice.chotard@st.com> Acked-by: Heiko Stuebner <heiko@sntech.de> Acked-by: Maxime Coquelin <maxime.coquelin@st.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers/pinctrl/vt8500')
-rw-r--r--drivers/pinctrl/vt8500/pinctrl-wmt.c12
1 files changed, 0 insertions, 12 deletions
diff --git a/drivers/pinctrl/vt8500/pinctrl-wmt.c b/drivers/pinctrl/vt8500/pinctrl-wmt.c
index 2c61281bebd7..8c976c21eeee 100644
--- a/drivers/pinctrl/vt8500/pinctrl-wmt.c
+++ b/drivers/pinctrl/vt8500/pinctrl-wmt.c
@@ -141,17 +141,6 @@ static int wmt_pmx_enable(struct pinctrl_dev *pctldev,
return wmt_set_pinmux(data, func_selector, pinnum);
}
-static void wmt_pmx_disable(struct pinctrl_dev *pctldev,
- unsigned func_selector,
- unsigned group_selector)
-{
- struct wmt_pinctrl_data *data = pinctrl_dev_get_drvdata(pctldev);
- u32 pinnum = data->pins[group_selector].number;
-
- /* disable by setting GPIO_IN */
- wmt_set_pinmux(data, WMT_FSEL_GPIO_IN, pinnum);
-}
-
static void wmt_pmx_gpio_disable_free(struct pinctrl_dev *pctldev,
struct pinctrl_gpio_range *range,
unsigned offset)
@@ -180,7 +169,6 @@ static struct pinmux_ops wmt_pinmux_ops = {
.get_function_name = wmt_pmx_get_function_name,
.get_function_groups = wmt_pmx_get_function_groups,
.enable = wmt_pmx_enable,
- .disable = wmt_pmx_disable,
.gpio_disable_free = wmt_pmx_gpio_disable_free,
.gpio_set_direction = wmt_pmx_gpio_set_direction,
};