mmc: pwrseq: add driver for emmc hardware reset (726b6324) · Commits · e / devices / android_kernel_fairphone_FP3

Documentation/devicetree/bindings/mmc/mmc-pwrseq-emmc.txt

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			* The simple eMMC hardware reset provider

			The purpose of this driver is to perform standard eMMC hw reset
			procedure, as descibed by Jedec 4.4 specification. This procedure is
			performed just after MMC core enabled power to the given mmc host (to
			fix possible issues if bootloader has left eMMC card in initialized or
			unknown state), and before performing complete system reboot (also in
			case of emergency reboot call). The latter is needed on boards, which
			doesn't have hardware reset logic connected to emmc card and (limited or
			broken) ROM bootloaders are unable to read second stage from the emmc
			card if the card is left in unknown or already initialized state.

			Required properties:
			- compatible : contains "mmc-pwrseq-emmc".
			- reset-gpios : contains a GPIO specifier. The reset GPIO is asserted
			and then deasserted to perform eMMC card reset. To perform
			reset procedure as described in Jedec 4.4 specification, the
			gpio line should be defined as GPIO_ACTIVE_LOW.

			Example:

			sdhci0_pwrseq {
			compatible = "mmc-pwrseq-emmc";
			reset-gpios = <&gpio1 12 GPIO_ACTIVE_LOW>;
			}

drivers/mmc/core/Makefile

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	@@ -8,5 +8,5 @@ mmc_core-y := core.o bus.o host.o \
	sdio.o sdio_ops.o sdio_bus.o \		sdio.o sdio_ops.o sdio_bus.o \
	sdio_cis.o sdio_io.o sdio_irq.o \		sdio_cis.o sdio_io.o sdio_irq.o \
	quirks.o slot-gpio.o		quirks.o slot-gpio.o
	mmc_core-$(CONFIG_OF) += pwrseq.o pwrseq_simple.o		mmc_core-$(CONFIG_OF) += pwrseq.o pwrseq_simple.o pwrseq_emmc.o
	mmc_core-$(CONFIG_DEBUG_FS) += debugfs.o		mmc_core-$(CONFIG_DEBUG_FS) += debugfs.o

drivers/mmc/core/pwrseq.c

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	@@ -26,6 +26,9 @@ static struct mmc_pwrseq_match pwrseq_match[] = {
	{		{
	.compatible = "mmc-pwrseq-simple",		.compatible = "mmc-pwrseq-simple",
	.alloc = mmc_pwrseq_simple_alloc,		.alloc = mmc_pwrseq_simple_alloc,
			}, {
			.compatible = "mmc-pwrseq-emmc",
			.alloc = mmc_pwrseq_emmc_alloc,
	},		},
	};		};

drivers/mmc/core/pwrseq.h

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	@@ -28,6 +28,7 @@ void mmc_pwrseq_power_off(struct mmc_host *host);
	void mmc_pwrseq_free(struct mmc_host *host);		void mmc_pwrseq_free(struct mmc_host *host);

	int mmc_pwrseq_simple_alloc(struct mmc_host host, struct device dev);		int mmc_pwrseq_simple_alloc(struct mmc_host host, struct device dev);
			int mmc_pwrseq_emmc_alloc(struct mmc_host host, struct device dev);

	#else		#else

drivers/mmc/core/pwrseq_emmc.c

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			/*
			* Copyright (C) 2015, Samsung Electronics Co., Ltd.
			*
			* Author: Marek Szyprowski <m.szyprowski@samsung.com>
			*
			* License terms: GNU General Public License (GPL) version 2
			*
			* Simple eMMC hardware reset provider
			*/
			#include <linux/delay.h>
			#include <linux/kernel.h>
			#include <linux/slab.h>
			#include <linux/device.h>
			#include <linux/err.h>
			#include <linux/gpio/consumer.h>
			#include <linux/reboot.h>

			#include <linux/mmc/host.h>

			#include "pwrseq.h"

			struct mmc_pwrseq_emmc {
			struct mmc_pwrseq pwrseq;
			struct notifier_block reset_nb;
			struct gpio_desc *reset_gpio;
			};

			static void __mmc_pwrseq_emmc_reset(struct mmc_pwrseq_emmc *pwrseq)
			{
			gpiod_set_value(pwrseq->reset_gpio, 1);
			udelay(1);
			gpiod_set_value(pwrseq->reset_gpio, 0);
			udelay(200);
			}

			static void mmc_pwrseq_emmc_reset(struct mmc_host *host)
			{
			struct mmc_pwrseq_emmc *pwrseq = container_of(host->pwrseq,
			struct mmc_pwrseq_emmc, pwrseq);

			__mmc_pwrseq_emmc_reset(pwrseq);
			}

			static void mmc_pwrseq_emmc_free(struct mmc_host *host)
			{
			struct mmc_pwrseq_emmc *pwrseq = container_of(host->pwrseq,
			struct mmc_pwrseq_emmc, pwrseq);

			unregister_restart_handler(&pwrseq->reset_nb);
			gpiod_put(pwrseq->reset_gpio);
			kfree(pwrseq);
			host->pwrseq = NULL;
			}

			static struct mmc_pwrseq_ops mmc_pwrseq_emmc_ops = {
			.post_power_on = mmc_pwrseq_emmc_reset,
			.free = mmc_pwrseq_emmc_free,
			};

			static int mmc_pwrseq_emmc_reset_nb(struct notifier_block *this,
			unsigned long mode, void *cmd)
			{
			struct mmc_pwrseq_emmc *pwrseq = container_of(this,
			struct mmc_pwrseq_emmc, reset_nb);

			__mmc_pwrseq_emmc_reset(pwrseq);
			return NOTIFY_DONE;
			}

			int mmc_pwrseq_emmc_alloc(struct mmc_host host, struct device dev)
			{
			struct mmc_pwrseq_emmc *pwrseq;
			int ret = 0;

			pwrseq = kzalloc(sizeof(struct mmc_pwrseq_emmc), GFP_KERNEL);
			if (!pwrseq)
			return -ENOMEM;

			pwrseq->reset_gpio = gpiod_get_index(dev, "reset", 0, GPIOD_OUT_LOW);
			if (IS_ERR(pwrseq->reset_gpio)) {
			ret = PTR_ERR(pwrseq->reset_gpio);
			goto free;
			}

			/*
			* register reset handler to ensure emmc reset also from
			* emergency_reboot(), priority 129 schedules it just before
			* system reboot
			*/
			pwrseq->reset_nb.notifier_call = mmc_pwrseq_emmc_reset_nb;
			pwrseq->reset_nb.priority = 129;
			register_restart_handler(&pwrseq->reset_nb);

			pwrseq->pwrseq.ops = &mmc_pwrseq_emmc_ops;
			host->pwrseq = &pwrseq->pwrseq;

			return 0;
			free:
			kfree(pwrseq);
			return ret;
			}