| Tom Rini | 53633a8 | 2024-02-29 12:33:36 -0500 | [diff] [blame] | 1 | # SPDX-License-Identifier: GPL-2.0 |
| 2 | %YAML 1.2 |
| 3 | --- |
| 4 | $id: http://devicetree.org/schemas/mmc/mmc-pwrseq-emmc.yaml# |
| 5 | $schema: http://devicetree.org/meta-schemas/core.yaml# |
| 6 | |
| 7 | title: Simple eMMC hardware reset provider |
| 8 | |
| 9 | maintainers: |
| 10 | - Ulf Hansson <ulf.hansson@linaro.org> |
| 11 | |
| 12 | description: |
| 13 | The purpose of this driver is to perform standard eMMC hw reset |
| 14 | procedure, as described by Jedec 4.4 specification. This procedure is |
| 15 | performed just after MMC core enabled power to the given mmc host (to |
| 16 | fix possible issues if bootloader has left eMMC card in initialized or |
| 17 | unknown state), and before performing complete system reboot (also in |
| 18 | case of emergency reboot call). The latter is needed on boards, which |
| 19 | doesn't have hardware reset logic connected to emmc card and (limited or |
| 20 | broken) ROM bootloaders are unable to read second stage from the emmc |
| 21 | card if the card is left in unknown or already initialized state. |
| 22 | |
| 23 | properties: |
| 24 | compatible: |
| 25 | const: mmc-pwrseq-emmc |
| 26 | |
| 27 | reset-gpios: |
| 28 | minItems: 1 |
| 29 | description: |
| 30 | contains a GPIO specifier. The reset GPIO is asserted |
| 31 | and then deasserted to perform eMMC card reset. To perform |
| 32 | reset procedure as described in Jedec 4.4 specification, the |
| 33 | gpio line should be defined as GPIO_ACTIVE_LOW. |
| 34 | |
| 35 | required: |
| 36 | - compatible |
| 37 | - reset-gpios |
| 38 | |
| 39 | additionalProperties: false |
| 40 | |
| 41 | examples: |
| 42 | - | |
| 43 | #include <dt-bindings/gpio/gpio.h> |
| 44 | pwrseq { |
| 45 | compatible = "mmc-pwrseq-emmc"; |
| 46 | reset-gpios = <&gpio1 12 GPIO_ACTIVE_LOW>; |
| 47 | }; |
| 48 | ... |