From: Stephen Boyd <sboyd@codeaurora.org> To: Timur Tabi <timur@codeaurora.org> Cc: Linus Walleij <linus.walleij@linaro.org>, Andy Gross <andy.gross@linaro.org>, David Brown <david.brown@linaro.org>, anjiandi@codeaurora.org, Bjorn Andersson <bjorn.andersson@linaro.org>, "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>, "thierry.reding@gmail.com" <thierry.reding@gmail.com>, Mika Westerberg <mika.westerberg@linux.intel.com>, Andy Shevchenko <andriy.shevchenko@linux.intel.com> Subject: Re: [PATCH 0/2] [v5] pinctrl: qcom: add support for sparse GPIOs Date: Tue, 3 Oct 2017 15:03:11 -0700 [thread overview] Message-ID: <20171003220311.GU457@codeaurora.org> (raw) In-Reply-To: <255ad0dc-2d16-ae7f-0b45-500e23cff1a4@codeaurora.org> On 09/22, Timur Tabi wrote: > On 09/22/2017 08:29 AM, Linus Walleij wrote: > > > >What is your response to Stephen's comment: > > > >>[Stephen Boyd] > >>Perhaps we can add another hook for our purposes here that > >>tells gpiolib that the gpio is not usable and to skip it. The > >>semantics would be clear, it's just about probing availability of > >>this pin as a gpio and doesn't mux any pins. > > >I think this kind of related to my response (after I realized it > >was not just about IRQs): > > We already have 95% of this. We can already specify individual pin > ranges, and the vast majority of the code recognizes the ranges. > There is only one small loophole, and that's in gpiochip_add_data(). > The for-loop iterates over all GPIOs: > > for (i = 0; i < chip->ngpio; i++) { > struct gpio_desc *desc = &gdev->descs[i]; > > desc->gdev = gdev; > /* > * REVISIT: most hardware initializes GPIOs as inputs > * (often with pullups enabled) so power usage is > * minimized. Linux code should set the gpio direction > * first thing; but until it does, and in case > * chip->get_direction is not set, we may expose the > * wrong direction in sysfs. > */ > > I believe the real problem is that this for-loop should be moved > from gpiochip_add_data() into some other function that is called > *after* the pin ranges are defined. We can put it in > gpiochip_add_pin_range(), maybe. > > My patch covers the loophole by adding a check inside > get_direction(). If we fix gpiochip_add_data(), I can remove that > patch. > > However, I think that change is risky and will require a lot of > testing and review. > I've run into this now on our mobile SoCs after I pull in commit 8e51533780ba ("pinctrl: qcom: add get_direction function"). Before that commit we never read each pin of the device. On our mobile SoCs we have devicetree and it feels like having that describe which pins are available and not available is half-duplicating information we would already have via consumers indicating which pins they care about. I don't see any value beyond system wide debug in figuring out the default pin configuration of a pin that doesn't have a consumer in Linux. Could we remove the pin direction finding part here in gpiochip_add_pin_range() and lazily resolve the pin direction when a pin is requested? We would need a similar check in the msm specific debugfs code where we skip pins that aren't requested. This is basically a revert of commit 72d320006177 ("gpio: set up initial state from .get_direction()"). ACPI can still describe only the pin ranges that they care about exposing, but from the devicetree side it's been working well enough to not touch pins that aren't used by anything in Linux. ---8<---- diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index cd003b74512f..673028823bc5 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -1210,16 +1210,7 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data) * wrong direction in sysfs. */ - if (chip->get_direction) { - /* - * If we have .get_direction, set up the initial - * direction flag from the hardware. - */ - int dir = chip->get_direction(chip, i); - - if (!dir) - set_bit(FLAG_IS_OUT, &desc->flags); - } else if (!chip->direction_input) { + if (!chip->direction_input) { /* * If the chip lacks the .direction_input callback * we logically assume all lines are outputs. diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c index 273badd92561..4a0aeceb42f1 100644 --- a/drivers/pinctrl/qcom/pinctrl-msm.c +++ b/drivers/pinctrl/qcom/pinctrl-msm.c @@ -24,7 +24,7 @@ #include <linux/pinctrl/pinconf.h> #include <linux/pinctrl/pinconf-generic.h> #include <linux/slab.h> -#include <linux/gpio.h> +#include <linux/gpio/driver.h> #include <linux/interrupt.h> #include <linux/spinlock.h> #include <linux/reboot.h> @@ -494,6 +494,12 @@ static void msm_gpio_dbg_show_one(struct seq_file *s, }; g = &pctrl->soc->groups[offset]; + + if (!gpiochip_is_requested(chip, gpio)) { + seq_printf(s, " %-8s:", g->name); + return; + } + ctl_reg = readl(pctrl->regs + g->ctl_reg); is_out = !!(ctl_reg & BIT(g->oe_bit)); -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
WARNING: multiple messages have this Message-ID (diff)
From: sboyd@codeaurora.org (Stephen Boyd) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 0/2] [v5] pinctrl: qcom: add support for sparse GPIOs Date: Tue, 3 Oct 2017 15:03:11 -0700 [thread overview] Message-ID: <20171003220311.GU457@codeaurora.org> (raw) In-Reply-To: <255ad0dc-2d16-ae7f-0b45-500e23cff1a4@codeaurora.org> On 09/22, Timur Tabi wrote: > On 09/22/2017 08:29 AM, Linus Walleij wrote: > > > >What is your response to Stephen's comment: > > > >>[Stephen Boyd] > >>Perhaps we can add another hook for our purposes here that > >>tells gpiolib that the gpio is not usable and to skip it. The > >>semantics would be clear, it's just about probing availability of > >>this pin as a gpio and doesn't mux any pins. > > >I think this kind of related to my response (after I realized it > >was not just about IRQs): > > We already have 95% of this. We can already specify individual pin > ranges, and the vast majority of the code recognizes the ranges. > There is only one small loophole, and that's in gpiochip_add_data(). > The for-loop iterates over all GPIOs: > > for (i = 0; i < chip->ngpio; i++) { > struct gpio_desc *desc = &gdev->descs[i]; > > desc->gdev = gdev; > /* > * REVISIT: most hardware initializes GPIOs as inputs > * (often with pullups enabled) so power usage is > * minimized. Linux code should set the gpio direction > * first thing; but until it does, and in case > * chip->get_direction is not set, we may expose the > * wrong direction in sysfs. > */ > > I believe the real problem is that this for-loop should be moved > from gpiochip_add_data() into some other function that is called > *after* the pin ranges are defined. We can put it in > gpiochip_add_pin_range(), maybe. > > My patch covers the loophole by adding a check inside > get_direction(). If we fix gpiochip_add_data(), I can remove that > patch. > > However, I think that change is risky and will require a lot of > testing and review. > I've run into this now on our mobile SoCs after I pull in commit 8e51533780ba ("pinctrl: qcom: add get_direction function"). Before that commit we never read each pin of the device. On our mobile SoCs we have devicetree and it feels like having that describe which pins are available and not available is half-duplicating information we would already have via consumers indicating which pins they care about. I don't see any value beyond system wide debug in figuring out the default pin configuration of a pin that doesn't have a consumer in Linux. Could we remove the pin direction finding part here in gpiochip_add_pin_range() and lazily resolve the pin direction when a pin is requested? We would need a similar check in the msm specific debugfs code where we skip pins that aren't requested. This is basically a revert of commit 72d320006177 ("gpio: set up initial state from .get_direction()"). ACPI can still describe only the pin ranges that they care about exposing, but from the devicetree side it's been working well enough to not touch pins that aren't used by anything in Linux. ---8<---- diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index cd003b74512f..673028823bc5 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -1210,16 +1210,7 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data) * wrong direction in sysfs. */ - if (chip->get_direction) { - /* - * If we have .get_direction, set up the initial - * direction flag from the hardware. - */ - int dir = chip->get_direction(chip, i); - - if (!dir) - set_bit(FLAG_IS_OUT, &desc->flags); - } else if (!chip->direction_input) { + if (!chip->direction_input) { /* * If the chip lacks the .direction_input callback * we logically assume all lines are outputs. diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c index 273badd92561..4a0aeceb42f1 100644 --- a/drivers/pinctrl/qcom/pinctrl-msm.c +++ b/drivers/pinctrl/qcom/pinctrl-msm.c @@ -24,7 +24,7 @@ #include <linux/pinctrl/pinconf.h> #include <linux/pinctrl/pinconf-generic.h> #include <linux/slab.h> -#include <linux/gpio.h> +#include <linux/gpio/driver.h> #include <linux/interrupt.h> #include <linux/spinlock.h> #include <linux/reboot.h> @@ -494,6 +494,12 @@ static void msm_gpio_dbg_show_one(struct seq_file *s, }; g = &pctrl->soc->groups[offset]; + + if (!gpiochip_is_requested(chip, gpio)) { + seq_printf(s, " %-8s:", g->name); + return; + } + ctl_reg = readl(pctrl->regs + g->ctl_reg); is_out = !!(ctl_reg & BIT(g->oe_bit)); -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
next prev parent reply other threads:[~2017-10-03 22:03 UTC|newest] Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-09-07 15:33 [PATCH 0/2] [v5] pinctrl: qcom: add support for sparse GPIOs Timur Tabi 2017-09-07 15:33 ` Timur Tabi 2017-09-07 15:33 ` [PATCH 1/2] [v5] pinctrl: qcom: disable GPIO groups with no pins Timur Tabi 2017-09-07 15:33 ` Timur Tabi 2017-10-02 17:44 ` Bjorn Andersson 2017-10-02 17:44 ` Bjorn Andersson 2017-10-02 20:47 ` Timur Tabi 2017-10-02 20:47 ` Timur Tabi 2017-10-07 11:07 ` Linus Walleij 2017-10-07 11:07 ` Linus Walleij 2017-10-13 23:35 ` Timur Tabi 2017-10-13 23:35 ` Timur Tabi 2017-10-19 22:44 ` Timur Tabi 2017-10-19 22:44 ` Timur Tabi 2017-10-16 8:01 ` Thierry Reding 2017-10-16 8:01 ` Thierry Reding 2017-10-16 13:52 ` Timur Tabi 2017-10-16 13:52 ` Timur Tabi 2017-09-07 15:33 ` [PATCH 2/2] [v3] pinctrl: qcom: qdf2xxx: add support for new ACPI HID QCOM8002 Timur Tabi 2017-09-07 15:33 ` Timur Tabi 2017-09-08 12:50 ` [PATCH 0/2] [v5] pinctrl: qcom: add support for sparse GPIOs Linus Walleij 2017-09-08 12:50 ` Linus Walleij 2017-09-13 17:09 ` Timur Tabi 2017-09-13 17:09 ` Timur Tabi 2017-09-19 7:04 ` Stephen Boyd 2017-09-19 7:04 ` Stephen Boyd 2017-09-19 8:15 ` Linus Walleij 2017-09-19 8:15 ` Linus Walleij 2017-09-19 12:32 ` Timur Tabi 2017-09-19 12:32 ` Timur Tabi 2017-09-20 11:43 ` Linus Walleij 2017-09-20 11:43 ` Linus Walleij 2017-09-20 13:04 ` Timur Tabi 2017-09-20 13:04 ` Timur Tabi 2017-09-21 12:08 ` Linus Walleij 2017-09-21 12:08 ` Linus Walleij 2017-09-21 12:12 ` Timur Tabi 2017-09-21 12:12 ` Timur Tabi 2017-09-22 13:29 ` Linus Walleij 2017-09-22 13:29 ` Linus Walleij 2017-09-22 13:37 ` Timur Tabi 2017-09-22 13:37 ` Timur Tabi 2017-10-03 22:03 ` Stephen Boyd [this message] 2017-10-03 22:03 ` Stephen Boyd 2017-10-03 22:12 ` Timur Tabi 2017-10-03 22:12 ` Timur Tabi 2017-10-04 21:50 ` Stephen Boyd 2017-10-04 21:50 ` Stephen Boyd 2017-10-04 22:41 ` Timur Tabi 2017-10-04 22:41 ` Timur Tabi 2017-10-05 21:30 ` Stephen Boyd 2017-10-05 21:30 ` Stephen Boyd 2017-10-11 7:51 ` Linus Walleij 2017-10-11 7:51 ` Linus Walleij 2017-10-12 7:39 ` Stephen Boyd 2017-10-12 7:39 ` Stephen Boyd 2017-10-14 22:43 ` Linus Walleij 2017-10-14 22:43 ` Linus Walleij 2017-10-16 13:42 ` Timur Tabi 2017-10-16 13:42 ` Timur Tabi 2017-10-13 23:26 ` Timur Tabi 2017-10-13 23:26 ` Timur Tabi 2017-10-15 20:18 ` Thierry Reding 2017-10-15 20:18 ` Thierry Reding 2017-10-15 21:09 ` Timur Tabi 2017-10-15 21:09 ` Timur Tabi 2017-10-02 16:02 ` Timur Tabi 2017-10-02 16:02 ` Timur Tabi
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