From: Tony Lindgren [mailto:tony@xxxxxxxxxxx] >* Gupta, Pekon <pekon@xxxxxx> [140519 21:07]: >> From: Tony Lindgren [mailto:tony@xxxxxxxxxxx] >> >* Pekon Gupta <pekon@xxxxxx> [140519 02:16]: >> >> Adds pinmux and DT node for Micron (MT29F4G08AB) x8 NAND device present on >> >> am437x-gp-evm board. >> >> (1) As NAND Flash data lines are muxed with eMMC, Thus at a given time either >> >> eMMC or NAND can be enabled. Selection between eMMC and NAND is controlled: >> >> (a) By dynamically driving following GPIO pin from software >> >> SPI2_CS0(GPIO) == 0 NAND is selected (default) >> >> SPI2_CS0(GPIO) == 1 eMMC is selected >> >> (b) By statically using Jumper (J89) on the board >> > >> >So which MMC controller has eMMC then? How do we select which one we >> >have enabled in the am437x-gp-evm.dts by default? >> > >> If there is no Jumper on the board, then driving SPI2_CS0 before device >> probe decides the selection between NAND and eMMC. Therefore NAND >> pin-mux also includes SPI2_CS0 and enables PULLDOWN on it to select NAND. > >So do they share lines outside omap, not inside omap? > >The reason I'm asking is I'm worried about the conflicting >pinctrl settings if we try to use both. And I guess that's >not an issue if the muxing of lines is done outside the >omap? > Yes, the muxing is outside OMAP SoC, so if SPI2_CS0 is correctly driven it will not allow contention on GPMC line (as per board design). On am437x-gp-evm board, SPI2_CS0 is used to: - route GPMC signals to selected device {eMMC | NAND}. - keep the de-selected device {eMMC | NAND} in reset. with regards, pekon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
