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Commit 0314cbd4 authored by Chen-Yu Tsai's avatar Chen-Yu Tsai Committed by Ulf Hansson
Browse files

mmc: sunxi: Document host init sequence 



sunxi_mmc_init_host() originated from Allwinner kernel sources. The
magic numbers written to various registers was never documented.

Add comments for values found in Allwinner user manuals.

Signed-off-by: default avatarChen-Yu Tsai <wens@csie.org>
Acked-by: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 9f24b0f2

drivers/mmc/host/sunxi-mmc.c

+12 −0
Original line number Diff line number Diff line
@@ -284,16 +284,28 @@ static int sunxi_mmc_init_host(struct mmc_host *mmc) 
	if (sunxi_mmc_reset_host(host))

		return -EIO;



	/*

	 * Burst 8 transfers, RX trigger level: 7, TX trigger level: 8

	 *

	 * TODO: sun9i has a larger FIFO and supports higher trigger values

	 */

	mmc_writel(host, REG_FTRGL, 0x20070008);

	/* Maximum timeout value */

	mmc_writel(host, REG_TMOUT, 0xffffffff);

	/* Unmask SDIO interrupt if needed */

	mmc_writel(host, REG_IMASK, host->sdio_imask);

	/* Clear all pending interrupts */

	mmc_writel(host, REG_RINTR, 0xffffffff);

	/* Debug register? undocumented */

	mmc_writel(host, REG_DBGC, 0xdeb);

	/* Enable CEATA support */

	mmc_writel(host, REG_FUNS, SDXC_CEATA_ON);

	/* Set DMA descriptor list base address */

	mmc_writel(host, REG_DLBA, host->sg_dma);



	rval = mmc_readl(host, REG_GCTRL);

	rval |= SDXC_INTERRUPT_ENABLE_BIT;

	/* Undocumented, but found in Allwinner code */

	rval &= ~SDXC_ACCESS_DONE_DIRECT;

	mmc_writel(host, REG_GCTRL, rval);