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mmc: sunxi: Document host init sequence

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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: Chen-Yu Tsai <wens@csie.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Chen-Yu Tsai 2016-01-21 13:26:28 +08:00 committed by Ulf Hansson
parent 9f24b0f254
commit 0314cbd438
1 changed files with 12 additions and 0 deletions
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12
drivers/mmc/host/sunxi-mmc.c
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@ -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);