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

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

Hi Jaehoon,

> On 03/05/2014 06:21 PM, Lukasz Majewski wrote:
> > 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
> Ok. It will be change to use the dt file.

That would be great. With DT support DW_MMC is even easier to enable.

> 
> > 
> > 
> > 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.
> DDR mode didn't implement at u-boot. It need to update code for DDR
> mode. 

Since SDHCI doesn't support DDR, with DW_MMC and DDR enabled, we shall
(theoretically at least) observe substantial data transmission speed up.

> If you want to use DDR mode, then i will implement it.

That would be great :-).


> 
> > 
> > However, I still believe, that DW_MMC with properly enabled DDR
> > could outperform SDHCI. 
> 
> Right, If DW-mmc is used with DDR mode, then it's more better than
> SDHCI. 

I agree here.

> there is no reason that we didn't use the dw-mmc controller at
> trats2 board.

If DW_MMC+DDR turns out to be faster than SDHCI, then we will use it.

> 
> > 
> > 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.
> Maybe, need to add Samsung-SoC maintainer, and base on SoC repository.
> 
> Best Regards,
> Jaehoon Chung
> > 
> >>
> >> 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