Adding esdhc4 eMMC support on mx6sabresd

[Shawn Guo]

On Thu, May 08, 2014 at 06:17:32PM +0800, Dong Aisheng wrote:
> I just tested an old Chris/mmc-next tree which is 3.14 rc2 with the top commit is b42b9b.
> The eMMC works well on SabreSD boards.
> But it failed and got the same issue with latest chris/mmc-next tree.
> I noticed there's no changes on sdhci-esdhc-imx.c
> Probably some other changes breaks this function.
> 
> Fabio,
> You may bisect it yourself or i will do it later when i'm a bit free.

The regression is caused by the following commit ...

commit 79f7ae7c45a6ccf04e2908337461dee615f6afb0
Author: Seungwon Jeon <tgih.jun at samsung.com>
Date:   Fri Mar 14 21:11:56 2014 +0900

    mmc: clarify DDR timing mode between SD-UHS and eMMC

    This change distinguishes DDR timing mode of current
    mixed usage to clarify device type.

    Signed-off-by: Seungwon Jeon <tgih.jun at samsung.com>
    Acked-by: Jaehoon Chung <jh80.chung at samsung.com>
    Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
    Signed-off-by: Chris Ball <chris at printf.net>

... and the line below.
 
@@ -1264,7 +1264,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
                                        goto err;
                        }
                        mmc_card_set_ddr_mode(card);
-                       mmc_set_timing(card->host, MMC_TIMING_UHS_DDR50);
+                       mmc_set_timing(card->host, MMC_TIMING_MMC_DDR52);
                        mmc_set_bus_width(card->host, bus_width);
                }
        }


> Shawn,
> I remember this patch should have been upstream through your tree long time ago.
> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-October/206446.html
> It seems somehow missed.

Ah, yes.  It got lost.

Shawn