172f47aecSJisheng Zhang# SPDX-License-Identifier: GPL-2.0 272f47aecSJisheng Zhang%YAML 1.2 372f47aecSJisheng Zhang--- 472f47aecSJisheng Zhang$id: http://devicetree.org/schemas/mmc/mmc-pwrseq-emmc.yaml# 572f47aecSJisheng Zhang$schema: http://devicetree.org/meta-schemas/core.yaml# 672f47aecSJisheng Zhang 784e85359SKrzysztof Kozlowskititle: Simple eMMC hardware reset provider 872f47aecSJisheng Zhang 972f47aecSJisheng Zhangmaintainers: 1072f47aecSJisheng Zhang - Ulf Hansson <ulf.hansson@linaro.org> 1172f47aecSJisheng Zhang 1272f47aecSJisheng Zhangdescription: 1372f47aecSJisheng Zhang The purpose of this driver is to perform standard eMMC hw reset 1472f47aecSJisheng Zhang procedure, as described by Jedec 4.4 specification. This procedure is 1572f47aecSJisheng Zhang performed just after MMC core enabled power to the given mmc host (to 1672f47aecSJisheng Zhang fix possible issues if bootloader has left eMMC card in initialized or 1772f47aecSJisheng Zhang unknown state), and before performing complete system reboot (also in 1872f47aecSJisheng Zhang case of emergency reboot call). The latter is needed on boards, which 1972f47aecSJisheng Zhang doesn't have hardware reset logic connected to emmc card and (limited or 2072f47aecSJisheng Zhang broken) ROM bootloaders are unable to read second stage from the emmc 2172f47aecSJisheng Zhang card if the card is left in unknown or already initialized state. 2272f47aecSJisheng Zhang 2372f47aecSJisheng Zhangproperties: 2472f47aecSJisheng Zhang compatible: 2572f47aecSJisheng Zhang const: mmc-pwrseq-emmc 2672f47aecSJisheng Zhang 2772f47aecSJisheng Zhang reset-gpios: 2872f47aecSJisheng Zhang minItems: 1 2972f47aecSJisheng Zhang description: 3072f47aecSJisheng Zhang contains a GPIO specifier. The reset GPIO is asserted 3172f47aecSJisheng Zhang and then deasserted to perform eMMC card reset. To perform 3272f47aecSJisheng Zhang reset procedure as described in Jedec 4.4 specification, the 3372f47aecSJisheng Zhang gpio line should be defined as GPIO_ACTIVE_LOW. 3472f47aecSJisheng Zhang 3572f47aecSJisheng Zhangrequired: 3672f47aecSJisheng Zhang - compatible 3772f47aecSJisheng Zhang - reset-gpios 3872f47aecSJisheng Zhang 395be478f9SRob HerringadditionalProperties: false 405be478f9SRob Herring 4172f47aecSJisheng Zhangexamples: 4272f47aecSJisheng Zhang - | 4372f47aecSJisheng Zhang #include <dt-bindings/gpio/gpio.h> 44*bb065c6fSKrzysztof Kozlowski pwrseq { 4572f47aecSJisheng Zhang compatible = "mmc-pwrseq-emmc"; 4672f47aecSJisheng Zhang reset-gpios = <&gpio1 12 GPIO_ACTIVE_LOW>; 4772f47aecSJisheng Zhang }; 4872f47aecSJisheng Zhang... 49