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authorReinhard Meyer <u-boot@emk-elektronik.de>2010-08-13 10:31:06 +0200
committerReinhard Meyer <u-boot@emk-elektronik.de>2010-09-03 11:19:01 +0200
commit1592ef8596fffd937a30462eb15f1d64e237ae49 (patch)
treea4d26cb016750db74bb1585ccb23753632452c53 /doc
parentc982d866eaee5e8469af9e22eb8f51c63adcfafa (diff)
AT91: MCI: add SD/MMC driver using mmc framework
Signed-off-by: Reinhard Meyer <u-boot@emk-elektronik.de>
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+How to use SD/MMC cards with Atmel SoCs having MCI hardware
+-----------------------------------------------------------
+2010-08-16 Reinhard Meyer <reinhard.meyer@emk-elektronik.de>
+
+This is a new approach to use Atmel MCI hardware with the
+general MMC framework. Therefore it benefits from that
+framework's abilities to handle SDHC Cards and the ability
+to write blocks.
+
+- AT91SAM9XE512 (tested, will definitely work with XE128 and XE256)
+- AT91SAM9260 (not tested, but MCI is to AT91SAM9XE)
+- AT91SAM9G20 (not tested, should work)
+
+It should work with all other ATMEL devices that have MCI,
+including AVR32.
+
+The generic driver does NOT assign port pins to the MCI block
+nor does it start the MCI clock. This has to be handled in a
+board/SoC specific manner before the driver is initialized:
+
+example: this is added to at91sam9260_devices.c:
+
+#if defined(CONFIG_ATMEL_MCI) || defined(CONFIG_GENERIC_ATMEL_MCI)
+void at91_mci_hw_init(void)
+{
+ at91_set_a_periph(AT91_PIO_PORTA, 8, PUP); /* MCCK */
+#if defined(CONFIG_ATMEL_MCI_PORTB)
+ at91_set_b_periph(AT91_PIO_PORTA, 1, PUP); /* MCCDB */
+ at91_set_b_periph(AT91_PIO_PORTA, 0, PUP); /* MCDB0 */
+ at91_set_b_periph(AT91_PIO_PORTA, 5, PUP); /* MCDB1 */
+ at91_set_b_periph(AT91_PIO_PORTA, 4, PUP); /* MCDB2 */
+ at91_set_b_periph(AT91_PIO_PORTA, 3, PUP); /* MCDB3 */
+#else
+ at91_set_a_periph(AT91_PIO_PORTA, 7, PUP); /* MCCDA */
+ at91_set_a_periph(AT91_PIO_PORTA, 6, PUP); /* MCDA0 */
+ at91_set_a_periph(AT91_PIO_PORTA, 9, PUP); /* MCDA1 */
+ at91_set_a_periph(AT91_PIO_PORTA, 10, PUP); /* MCDA2 */
+ at91_set_a_periph(AT91_PIO_PORTA, 11, PUP); /* MCDA3 */
+#endif
+}
+#endif
+
+the board specific file need added:
+...
+#ifdef CONFIG_GENERIC_ATMEL_MCI
+# include <mmc.h>
+#endif
+...
+#ifdef CONFIG_GENERIC_ATMEL_MCI
+/* this is a weak define that we are overriding */
+int board_mmc_init(bd_t *bd)
+{
+ /* Enable clock */
+ at91_sys_write(AT91_PMC_PCER, 1 << AT91SAM9260_ID_MCI);
+ at91_mci_hw_init();
+
+ /* This calls the atmel_mci_init in gen_atmel_mci.c */
+ return atmel_mci_init((void *)AT91_BASE_MCI);
+}
+
+/* this is a weak define that we are overriding */
+int board_mmc_getcd(u8 *cd, struct mmc *mmc)
+{
+ /*
+ * the only currently existing use of this function
+ * (fsl_esdhc.c) suggests this function must return
+ * *cs = TRUE if a card is NOT detected -> in most
+ * cases the value of the pin when the detect switch
+ * closes to GND
+ */
+ *cd = at91_get_gpio_value (CONFIG_SYS_MMC_CD_PIN) ? 1 : 0;
+ return 0;
+}
+
+#endif
+
+and the board definition files needs:
+
+/* SD/MMC card */
+#define CONFIG_MMC 1
+#define CONFIG_GENERIC_MMC 1
+#define CONFIG_GENERIC_ATMEL_MCI 1
+#define CONFIG_ATMEL_MCI_PORTB 1 /* Atmel XE-EK uses port B */
+#define CONFIG_SYS_MMC_CD_PIN AT91_PIN_PC9
+#define CONFIG_CMD_MMC 1
+