[U-Boot] [PATCH 0/3] samsung: Add mmc controller to use dw mmc

[Lukasz Majewski <l.majewski@samsung.com>]

Hi Beomho,

> This patch set for use dw mmc controller.
> First, add dw mmc controller initialization.
> And then, change exynos4 mmc gpio configuration.
> Additionally, I have removed exynos4x12_set_mmc_clk function.
> Because samsung_get_base_clock() (exynos4x12/ exynos4) return same
> value.

Thank you for supporting the DW_MMC on Trats2.

I've got following comments:

1. Piotr Wilczek (added to CC) is moving the Trats/Trats2 board to
support configuration via device tree. From device tree it is easier to
seamlessly enable support for DW_MMC (SDMMC4 controller) - at least we
would avoid adding new #ifdefs. The way to enable it is almost
identical to Exynos5250 (board "snow").

Now the v4 has been sent, so please look (and probably rebase your work)
on them:

"[PATCH V4 00/12] Exynos4: add support for device tree"
http://article.gmane.org/gmane.comp.boot-loaders.u-boot/181576/match=exynos4+add+support+device+tree


2. We did some rough tests for the DW_MMC implementation on Trats2 (with
clock phase settings similar to the one in the kernel) and it turned
out that SDHCI is faster. 

Two possible explanations:
- DDR is not supported by memory embedded on Trats2
- We did something wrong, so as a result the DDR mode for
  DW_MMC/eMMC memory was not working properly.

However, I still believe, that DW_MMC with properly enabled DDR could
outperform SDHCI. 

Why this speedup is important? 

We struggle to reduce time needed for flashing large images (like
rootfs - e.g. 400 MiB in size).

Any help is more than welcome :-).


3. u-boot general advice:

When you alter things related to a particular board (like
trats2 in this case) it is welcome to add the board's maintainer to CC.
You can find them at boards.cfg.

> 
> This patch set is tested on Trats2 board.
> 
> Beomho Seo (3):
>   board: samsung: trats2: Add DW MMC controller initialization
>   arm: exynos: pinmux: Add sdmmc4 gpio confifuration
>   arm: exynos: clock: Remove exynos4x12_set_mmc_clk function
> 
>  arch/arm/cpu/armv7/exynos/clock.c  |   29
> +---------------------------- arch/arm/cpu/armv7/exynos/pinmux.c |
> 20 +++++++++++++++----- board/samsung/trats2/trats2.c      |   31
> +++++++++++++++++++++---------- 3 files changed, 37 insertions(+), 43
> deletions(-)



-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group