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How to use SD/MMC cards with Atmel SoCs having MCI hardware
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-----------------------------------------------------------
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2010-08-16 Reinhard Meyer <reinhard.meyer@emk-elektronik.de>
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This is a new approach to use Atmel MCI hardware with the
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general MMC framework. Therefore it benefits from that
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framework's abilities to handle SDHC Cards and the ability
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to write blocks.
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- AT91SAM9XE512 (tested, will definitely work with XE128 and XE256)
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- AT91SAM9260 (not tested, but MCI is to AT91SAM9XE)
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- AT91SAM9G20 (not tested, should work)
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It should work with all other ATMEL devices that have MCI,
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including AVR32.
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The generic driver does NOT assign port pins to the MCI block
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nor does it start the MCI clock. This has to be handled in a
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board/SoC specific manner before the driver is initialized:
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example: this is added to at91sam9260_devices.c:
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#if defined(CONFIG_GENERIC_ATMEL_MCI)
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void at91_mci_hw_init(void)
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{
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at91_set_a_periph(AT91_PIO_PORTA, 8, PUP); /* MCCK */
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#if defined(CONFIG_ATMEL_MCI_PORTB)
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at91_set_b_periph(AT91_PIO_PORTA, 1, PUP); /* MCCDB */
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at91_set_b_periph(AT91_PIO_PORTA, 0, PUP); /* MCDB0 */
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at91_set_b_periph(AT91_PIO_PORTA, 5, PUP); /* MCDB1 */
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at91_set_b_periph(AT91_PIO_PORTA, 4, PUP); /* MCDB2 */
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at91_set_b_periph(AT91_PIO_PORTA, 3, PUP); /* MCDB3 */
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#else
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at91_set_a_periph(AT91_PIO_PORTA, 7, PUP); /* MCCDA */
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at91_set_a_periph(AT91_PIO_PORTA, 6, PUP); /* MCDA0 */
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at91_set_a_periph(AT91_PIO_PORTA, 9, PUP); /* MCDA1 */
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at91_set_a_periph(AT91_PIO_PORTA, 10, PUP); /* MCDA2 */
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at91_set_a_periph(AT91_PIO_PORTA, 11, PUP); /* MCDA3 */
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#endif
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}
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#endif
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the board specific file need added:
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...
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#ifdef CONFIG_GENERIC_ATMEL_MCI
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# include <mmc.h>
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#endif
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...
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#ifdef CONFIG_GENERIC_ATMEL_MCI
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/* this is a weak define that we are overriding */
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int board_mmc_init(bd_t *bd)
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{
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/* Enable clock */
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at91_sys_write(AT91_PMC_PCER, 1 << AT91SAM9260_ID_MCI);
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at91_mci_hw_init();
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/* This calls the atmel_mci_init in gen_atmel_mci.c */
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return atmel_mci_init((void *)AT91_BASE_MCI);
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}
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/* this is a weak define that we are overriding */
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int board_mmc_getcd(struct mmc *mmc)
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{
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return !at91_get_gpio_value(CONFIG_SYS_MMC_CD_PIN);
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}
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#endif
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and the board definition files needs:
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/* SD/MMC card */
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#define CONFIG_GENERIC_ATMEL_MCI 1
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#define CONFIG_ATMEL_MCI_PORTB 1 /* Atmel XE-EK uses port B */
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#define CONFIG_SYS_MMC_CD_PIN AT91_PIN_PC9
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#define CONFIG_CMD_MMC 1
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