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Diffstat (limited to 'Documentation/devicetree/bindings/mmc/mmc-pwrseq-emmc.txt')
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1 files changed, 25 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/mmc/mmc-pwrseq-emmc.txt b/Documentation/devicetree/bindings/mmc/mmc-pwrseq-emmc.txt new file mode 100644 index 000000000000..0cb827bf9435 --- /dev/null +++ b/Documentation/devicetree/bindings/mmc/mmc-pwrseq-emmc.txt | |||
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1 | * The simple eMMC hardware reset provider | ||
2 | |||
3 | The purpose of this driver is to perform standard eMMC hw reset | ||
4 | procedure, as descibed by Jedec 4.4 specification. This procedure is | ||
5 | performed just after MMC core enabled power to the given mmc host (to | ||
6 | fix possible issues if bootloader has left eMMC card in initialized or | ||
7 | unknown state), and before performing complete system reboot (also in | ||
8 | case of emergency reboot call). The latter is needed on boards, which | ||
9 | doesn't have hardware reset logic connected to emmc card and (limited or | ||
10 | broken) ROM bootloaders are unable to read second stage from the emmc | ||
11 | card if the card is left in unknown or already initialized state. | ||
12 | |||
13 | Required properties: | ||
14 | - compatible : contains "mmc-pwrseq-emmc". | ||
15 | - reset-gpios : contains a GPIO specifier. The reset GPIO is asserted | ||
16 | and then deasserted to perform eMMC card reset. To perform | ||
17 | reset procedure as described in Jedec 4.4 specification, the | ||
18 | gpio line should be defined as GPIO_ACTIVE_LOW. | ||
19 | |||
20 | Example: | ||
21 | |||
22 | sdhci0_pwrseq { | ||
23 | compatible = "mmc-pwrseq-emmc"; | ||
24 | reset-gpios = <&gpio1 12 GPIO_ACTIVE_LOW>; | ||
25 | } | ||