Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932743AbaLBAWz (ORCPT ); Mon, 1 Dec 2014 19:22:55 -0500 Received: from arroyo.ext.ti.com ([192.94.94.40]:45719 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932382AbaLBAWx (ORCPT ); Mon, 1 Dec 2014 19:22:53 -0500 Date: Mon, 1 Dec 2014 18:22:45 -0600 From: Benoit Parrot To: Alexandre Courbot CC: Pantelis Antoniou , Jiri Prchal , Maxime Ripard , Linus Walleij , "linux-gpio@vger.kernel.org" , Linux Kernel Mailing List , "devicetree@vger.kernel.org" Subject: Re: [Patch v2 1/2] gpio: add GPIO hogging mechanism Message-ID: <20141202002244.GB24551@ti.com> References: <1416527684-19017-1-git-send-email-bparrot@ti.com> <1416527684-19017-2-git-send-email-bparrot@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alexandre Courbot wrote on Fri [2014-Nov-28 16:30:01 +0900]: > On Fri, Nov 21, 2014 at 8:54 AM, Benoit Parrot wrote: > > Based on Boris Brezillion's work this is a reworked patch > > of his initial GPIO hogging mechanism. > > This patch provides a way to initally configure specific GPIO > > when the gpio controller is probed. > > > > The actual DT scanning to collect the GPIO specific data is performed > > as part of the gpiochip_add(). > > > > The purpose of this is to allows specific GPIOs to be configured > > without any driver specific code. > > This particularly useful because board design are getting > > increasingly complex and given SoC pins can now have upward > > of 10 mux values a lot of connections are now dependent on > > external IO muxes to switch various modes and combination. > > > > Specific drivers should not necessarily need to be aware of > > what accounts to a specific board implementation. This board level > > "description" should be best kept as part of the dts file. > > > > Signed-off-by: Benoit Parrot > > --- > > Changes since v1: > > * Refactor the gpio-hog mechanism as private functions meant to > > be to invoked from of_gpiochip_add(). > > > > drivers/gpio/gpiolib-of.c | 188 ++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 188 insertions(+) > > > > diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c > > index 604dbe6..3caed76 100644 > > --- a/drivers/gpio/gpiolib-of.c > > +++ b/drivers/gpio/gpiolib-of.c > > @@ -22,6 +22,7 @@ > > #include > > #include > > #include > > +#include > > > > #include "gpiolib.h" > > > > @@ -111,6 +112,184 @@ int of_get_named_gpio_flags(struct device_node *np, const char *list_name, > > EXPORT_SYMBOL(of_get_named_gpio_flags); > > > > /** > > + * of_get_gpio_hog() - Get a GPIO hog descriptor, names and flags for GPIO API > > + * @np: device node to get GPIO from > > + * @name: GPIO line name > > + * @flags: a flags pointer to fill in > > + * > > + * Returns GPIO descriptor to use with Linux GPIO API, or one of the errno > > + * value on the error condition. > > + */ > > + > > +static struct gpio_desc *of_get_gpio_hog(struct device_node *np, > > + const char **name, > > + enum gpio_lookup_flags *lflags, > > + enum gpiod_flags *dflags) > > +{ > > + struct device_node *chip_np; > > + enum of_gpio_flags xlate_flags; > > + struct gpio_desc *desc; > > + struct gg_data gg_data = { > > + .flags = &xlate_flags, > > + .out_gpio = NULL, > > + }; > > + u32 tmp; > > + int i, in, outlo, outhi; > > + int ret; > > + > > + if (!np) > > + return ERR_PTR(-EINVAL); > > This function is being called from a perfectly mastered context in > this file, so maybe we can avoid this check. You are correct, I will change this. > > > + > > + chip_np = np->parent; > > + if (!chip_np) { > > + desc = ERR_PTR(-EINVAL); > > + goto out; > > + } > > + > > + if (!lflags || !dflags) { > > + desc = ERR_PTR(-EINVAL); > > + goto out; > > + } > > Same for this one. Agreed. > > > + > > + *lflags = 0; > > + *dflags = 0; > > + in = 0; > > + outlo = 0; > > + outhi = 0; > > + > > + ret = of_property_read_u32(chip_np, "#gpio-cells", &tmp); > > + if (ret) { > > + desc = ERR_PTR(ret); > > + goto out; > > Please use "return ERR_PTR(ret);" directly, since you do absolutely no > cleanup in out:. Same remark everywhere it applies. Agreed. > > > + } > > + > > + if (tmp > MAX_PHANDLE_ARGS) { > > + desc = ERR_PTR(-EINVAL); > > + goto out; > > + } > > + > > + gg_data.gpiospec.args_count = tmp; > > + gg_data.gpiospec.np = chip_np; > > + for (i = 0; i < tmp; i++) { > > + ret = of_property_read_u32(np, "gpios", > > + &gg_data.gpiospec.args[i]); > > + if (ret) { > > + desc = ERR_PTR(ret); > > + goto out; > > + } > > + } > > + > > + gpiochip_find(&gg_data, of_gpiochip_find_and_xlate); > > This seems to work but only supports one GPIO per hog node. It would > be nice to be able to specify several GPIOs to which the same settings > need to be applied. This is on purpose following Linus Walleij's comment. > > > + if (!gg_data.out_gpio) { > > + if (np->parent == np) > > + desc = ERR_PTR(-ENXIO); > > + else > > + desc = ERR_PTR(-EPROBE_DEFER); > > + goto out; > > + } > > + > > + if (xlate_flags & OF_GPIO_ACTIVE_LOW) > > + *lflags |= GPIOF_ACTIVE_LOW; > > + > > + if (of_property_read_bool(np, "input")) { > > + *dflags |= GPIOD_IN; > > + in = 1; > > + } > > + if (of_property_read_bool(np, "output-low")) { > > + *dflags |= GPIOD_OUT_LOW; > > + outlo = 1; > > + } > > + if (of_property_read_bool(np, "output-high")) { > > + *dflags |= GPIOD_OUT_HIGH; > > + outhi = 1; > > + } > > I thought we agreed that this should be a "direction = > input|output-low|output-high" property? Yes, miss that my bad. I'll change it, so it will only look for a single "direction" node, and hopefully simplify this mess. > > > + if ((in + outlo + outhi) > 1) { > > + pr_warn("%s: GPIO %s: more than one direction/value selected, assuming: %s.\n", > > + __func__, np->name, > > + (outhi)?"output-high":(outlo)?"output-low":"input"); > > + } > > + > > + if (of_property_read_bool(np, "open-drain-line")) > > + *lflags |= GPIO_OPEN_DRAIN; > > + if (of_property_read_bool(np, "open-source-line")) > > + *lflags |= GPIO_OPEN_SOURCE; > > These properties are not documented in your DT bindings. Yeah I'll remove those as they might as well be covered under the "xlate_flags" instead similar to GPIO_ACTIVE_LOW or whenever it gets propagated. > > > + if (name && of_property_read_string(np, "line-name", name)) > > + *name = np->name; > > + > > + desc = gg_data.out_gpio; > > + > > +out: > > + return desc; > > +} > > + > > + > > +/** > > + * do_gpio_hog - Given node is a GPIO hog configuration, handle it > > + * @np: device node to get GPIO from > > + * > > + * This is only used by of_gpiochip_add to request/set GPIO initial > > + * configuration. > > + */ > > +static int do_gpio_hog(struct device_node *np) > > +{ > > + struct gpio_desc *desc = NULL; > > + int err; > > + const char *name; > > + enum gpio_lookup_flags lflags; > > + enum gpiod_flags dflags; > > + > > + desc = of_get_gpio_hog(np, &name, &lflags, &dflags); > > + if (!desc) > > + return -ENOTSUPP; > > + else if (IS_ERR(desc)) > > + return PTR_ERR(desc); > > + > > + err = gpiod_request(desc, name); > > Using this function means that a GPIO chip module cannot be unloaded > if it uses GPIO hogs. Is it the intended behavior? If not, please use > gpiochip_request_own_desc() instead, and make sure to call > gpiochip_free_own_desc() for each hog when the driver is unloaded. So I guess we could add a undo_gpio_hog() function and hook it up under of_gpiochip_remove(). Now instead of maintaining a seperate structure just to keep track of hogged descriptor, would it be acceptable to add a new "gpio_desc.flags" value in gpiolib.h says: #define FLAG_GPIO_IS_HOGGED 10 And key on that at removal time instead of creating a list and having to maintain that? > > > + if (err < 0) > > + return err; > > + > > + if (lflags & GPIO_ACTIVE_LOW) > > + set_bit(FLAG_ACTIVE_LOW, &desc->flags); > > + if (lflags & GPIO_OPEN_DRAIN) > > + set_bit(FLAG_OPEN_DRAIN, &desc->flags); > > + if (lflags & GPIO_OPEN_SOURCE) > > + set_bit(FLAG_OPEN_SOURCE, &desc->flags); > > + > > + /* No particular flag request, not really hogging then... */ > > + if (!(dflags & GPIOD_FLAGS_BIT_DIR_SET)) { > > + pr_warn("%s: GPIO %s: no hogging direction specified, bailing out\n", > > + __func__, name); > > + err = -EINVAL; > > + goto free_gpio; > > + } > > + > > + /* Process flags */ > > + if (dflags & GPIOD_FLAGS_BIT_DIR_OUT) > > + err = gpiod_direction_output(desc, > > + dflags & GPIOD_FLAGS_BIT_DIR_VAL); > > + else > > + err = gpiod_direction_input(desc); > > + > > + if (err < 0) { > > + pr_warn("%s: GPIO %s setting direction/value failed\n", > > + __func__, name); > > + goto free_gpio; > > + } > > I would suggest to factorize this code that is similar to the one > found in __gpiod_get_index(). Do all the DT parsing in a function that > just returns a descriptor and the I would tend to agree. But as Linus suggested I was trying to contain the changes to gpiolib_of.c only. > > > + > > + pr_debug("%s: gpio-hog: GPIO:%d (%s) as %s%s\n", __func__, > > + desc_to_gpio(desc), name, > > + (dflags&GPIOD_FLAGS_BIT_DIR_OUT) ? "output" : "input", > > + (dflags&GPIOD_FLAGS_BIT_DIR_OUT) ? > > + (dflags&GPIOD_FLAGS_BIT_DIR_VAL) ? "/high" : "/low":""); > > + > > + return 0; > > + > > +free_gpio: > > + gpiod_put(desc); > > + return err; > > +} > > I think most of this function should be moved into gpiolib.c. Add a > function there that takes the descriptor, lflags and dflags and that > sets the GPIO up, possibly adding it to a list of hogs so we can unset > the hogs when unloading the module. That way we have a hogging > mechanism that is not dependent on device tree and can be used by > other GPIO binders, such as ACPI. > That's fine with as long as everyone agrees. > There is still some work needed but it looks much better than the > first version. Please make sure to also keep Maxime, Pantelis and Jiri > in the loop since they expressed interest in your first version. Regards, Benoit -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/