[PATCH V2 4/4] mmc: pwrseq_simple: Add support for a reset GPIO pin
From: mark.rutland@arm.com (Mark Rutland)
Date: 2015-01-15 17:04:44
Also in:
linux-devicetree, linux-mmc
Hi, On Wed, Jan 14, 2015 at 01:02:10PM +0000, Ulf Hansson wrote:
The need for a reset GPIO has several times been pointed out from earlier posted patchsets. Especially some WLAN chips which are attached to an SDIO interface may use a GPIO reset. In this first version, one reset pin is supported. We may want to extend the support to cover more pins, but let's leave that as a future change. The added DT binding for the reset GPIO can easily be extended to manage several pins. The reset GPIO is asserted at initialization and prior we start the power up procedure. It will then be de-asserted right after the power has been provided to the external chip/card, from the ->post_power_on() callback.
This needs to be specified a little more explicitly in the binding document below, as it forms part of the contract of the binding.
quoted hunk ↗ jump to hunk
Note, the reset GPIO is optional. Thus we don't return an error even if we can't find a GPIO pin for the consumer. Signed-off-by: Ulf Hansson <redacted> --- Changes in v2: - Adopted to the changed names of the pwrseq callbacks. --- .../devicetree/bindings/mmc/mmc,pwrseq-simple.txt | 5 +++ drivers/mmc/core/pwrseq_simple.c | 38 ++++++++++++++++++++++ 2 files changed, 43 insertions(+)diff --git a/Documentation/devicetree/bindings/mmc/mmc,pwrseq-simple.txt b/Documentation/devicetree/bindings/mmc/mmc,pwrseq-simple.txt index e1b7f9c..6fe0cd6 100644 --- a/Documentation/devicetree/bindings/mmc/mmc,pwrseq-simple.txt +++ b/Documentation/devicetree/bindings/mmc/mmc,pwrseq-simple.txt@@ -11,8 +11,13 @@ for several SOC designs. Required properties: - compatible : contains "mmc,pwrseq-simple". +Optional properties: +- reset-gpios : contains a list of GPIO specifiers, though currently only one + specifier is supported.
The support is a Linux issue. If the binding is meant to describe a list, mention that, and what the expected semantics are. Is it that difficult to have the driver iterate over the list now? Thanks, Mark.
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+ Example: sdhci0_pwrseq { compatible = "mmc,pwrseq-simple"; + reset-gpios = <&gpio1 12 0>; }diff --git a/drivers/mmc/core/pwrseq_simple.c b/drivers/mmc/core/pwrseq_simple.c index 7f87bc1..42d9836 100644 --- a/drivers/mmc/core/pwrseq_simple.c +++ b/drivers/mmc/core/pwrseq_simple.c@@ -11,6 +11,7 @@ #include <linux/slab.h> #include <linux/device.h> #include <linux/err.h> +#include <linux/gpio/consumer.h> #include <linux/mmc/host.h>@@ -18,31 +19,68 @@ struct mmc_pwrseq_simple { struct mmc_pwrseq pwrseq; + struct gpio_desc *reset_gpio; }; +static void mmc_pwrseq_simple_pre_power_on(struct mmc_host *host) +{ + struct mmc_pwrseq_simple *pwrseq = container_of(host->pwrseq, + struct mmc_pwrseq_simple, pwrseq); + + if (!IS_ERR(pwrseq->reset_gpio)) + gpiod_set_value_cansleep(pwrseq->reset_gpio, 1); +} + +static void mmc_pwrseq_simple_post_power_on(struct mmc_host *host) +{ + struct mmc_pwrseq_simple *pwrseq = container_of(host->pwrseq, + struct mmc_pwrseq_simple, pwrseq); + + if (!IS_ERR(pwrseq->reset_gpio)) + gpiod_set_value_cansleep(pwrseq->reset_gpio, 0); +} + static void mmc_pwrseq_simple_free(struct mmc_host *host) { struct mmc_pwrseq_simple *pwrseq = container_of(host->pwrseq, struct mmc_pwrseq_simple, pwrseq); + if (!IS_ERR(pwrseq->reset_gpio)) + gpiod_put(pwrseq->reset_gpio); + kfree(&pwrseq); host->pwrseq = NULL; } static struct mmc_pwrseq_ops mmc_pwrseq_simple_ops = { + .pre_power_on = mmc_pwrseq_simple_pre_power_on, + .post_power_on = mmc_pwrseq_simple_post_power_on, + .power_off = mmc_pwrseq_simple_pre_power_on, .free = mmc_pwrseq_simple_free, }; int mmc_pwrseq_simple_alloc(struct mmc_host *host, struct device *dev) { struct mmc_pwrseq_simple *pwrseq; + int ret = 0; pwrseq = kzalloc(sizeof(struct mmc_pwrseq_simple), GFP_KERNEL); if (!pwrseq) return -ENOMEM; + pwrseq->reset_gpio = gpiod_get_index(dev, "reset", 0, GPIOD_OUT_HIGH); + if (IS_ERR(pwrseq->reset_gpio) && + PTR_ERR(pwrseq->reset_gpio) != -ENOENT && + PTR_ERR(pwrseq->reset_gpio) != -ENOSYS) { + ret = PTR_ERR(pwrseq->reset_gpio); + goto free; + } + pwrseq->pwrseq.ops = &mmc_pwrseq_simple_ops; host->pwrseq = &pwrseq->pwrseq; return 0; +free: + kfree(&pwrseq); + return ret; }-- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html