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This patch provides a simple mmc-pwrseq-emmc driver, which controls single gpio line. It 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. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
26 lines
1.1 KiB
Plaintext
26 lines
1.1 KiB
Plaintext
* 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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procedure, as descibed by Jedec 4.4 specification. This procedure is
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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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