2015-02-03 21:07:53 +08:00
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* The simple eMMC hardware reset provider
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The purpose of this driver is to perform standard eMMC hw reset
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2016-04-25 08:24:13 +08:00
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procedure, as described by Jedec 4.4 specification. This procedure is
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2015-02-03 21:07:53 +08:00
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performed just after MMC core enabled power to the given mmc host (to
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fix possible issues if bootloader has left eMMC card in initialized or
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unknown state), and before performing complete system reboot (also in
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case of emergency reboot call). The latter is needed on boards, which
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doesn't have hardware reset logic connected to emmc card and (limited or
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broken) ROM bootloaders are unable to read second stage from the emmc
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card if the card is left in unknown or already initialized state.
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Required properties:
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- compatible : contains "mmc-pwrseq-emmc".
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- reset-gpios : contains a GPIO specifier. The reset GPIO is asserted
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and then deasserted to perform eMMC card reset. To perform
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reset procedure as described in Jedec 4.4 specification, the
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gpio line should be defined as GPIO_ACTIVE_LOW.
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Example:
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sdhci0_pwrseq {
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compatible = "mmc-pwrseq-emmc";
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reset-gpios = <&gpio1 12 GPIO_ACTIVE_LOW>;
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}
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