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[RFC,01/15] mmc: sunxi: Document host init sequence

Message ID 1453354002-28366-2-git-send-email-wens@csie.org (mailing list archive)
State New, archived
Headers show

Commit Message

Chen-Yu Tsai Jan. 21, 2016, 5:26 a.m. UTC
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>
---
 drivers/mmc/host/sunxi-mmc.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Comments

Ulf Hansson Jan. 29, 2016, 11:39 a.m. UTC | #1
On 21 January 2016 at 06:26, Chen-Yu Tsai <wens@csie.org> wrote:
> 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>

Thanks, applied for next!

Kind regards
Uffe

> ---
>  drivers/mmc/host/sunxi-mmc.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> index 83de82bceafc..cce5ca540857 100644
> --- a/drivers/mmc/host/sunxi-mmc.c
> +++ b/drivers/mmc/host/sunxi-mmc.c
> @@ -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);
>
> --
> 2.7.0.rc3
>
diff mbox

Patch

diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
index 83de82bceafc..cce5ca540857 100644
--- a/drivers/mmc/host/sunxi-mmc.c
+++ b/drivers/mmc/host/sunxi-mmc.c
@@ -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);