[PATCH v6 0/5] Add enhanced strobe support for emmc version 5.1 or later

[Ulf Hansson]

On 26 May 2016 at 03:55, Shawn Lin <shawn.lin at rock-chips.com> wrote:
>
> Hello all,
>
> This patch is going to support enhanced strobe function
> for emmc version 5.1+ introduced by JEDEC recently.
>
> Enchanced strobe is a optional function, so we add a new cap* for drivers to
> decide whether to use it.
>
> When introduing hs400 mode, JEDEC asks controllers to use data strobe line
> to latch the data from emmc devives. But for cmd-reponse, not mentioned yet.
> Since emmc version 5.1 published, JEDEC adds enhanced strobe function to deal
> with cmd-response the same way as data-read. This feature is optional.
>
> From the spec(section 6.6.2.3), the standard scenario to select HS400 enhanced
> strobe mode illustrated like this:
> (1) set HS_TIMIMG (Highspeed)
> (2) Host change freq to <= 52Mhz
> (3) set the bus width to Enhanced strobe and DDR8Bit(CMD6), EXT_CSD[183] = 0x86
> instead of 0x80
> (4) set HS_TIMING to 0x3 (HS400)
> (5) Host change freq to <= 200Mhz
> (6) Host select HS400 enhanced strobe complete
>
> I can't find a upstreamed controller claimed to support it, as well as the
> mmc stack. But my "arasan,sdhci-5.1" actually supports this function. So I decide
> to work for this part.
>
> By looking into the SDHCI spec, I find there isn't any registers to enable the
> enhanced strobe function. But from my "arasan,sdhci-5.1" databook, it describes a
> register called VENDOR_REGISTER(0x78) to trigger this mode. So I guess other sdhci
> variant drivers may also need s vendor specific register to deal with it.
>
> If we are sure that our controller supports enhanced strobe mode, just add
> mmc-hs400-enhanced-strobe in DT. Once emmc devices claims to support this mode,
> we enable it automatically. Of course, other sdhci*/non-sdhci drivers should
> implement/overwrite the hs400_enhanced_strobe by themselves. I believe all of the
> platforms which need to support this mode should do some basic preparation for their
> controllers. Currently I just limit the callback within ths scope of arasan,sdhci-5.1,
> but I prone to believe arasan will use VENDOR_REGISTER to tirgger this mode from now on
> because I do believe vendor will consider the registers' compatibility.
>
> With this patchset applied, we can successfully run in HS400 enhanced strobe mode on
> RK3399 platform with Samsung eMMC KLMBG2JENB-B041(v5.1, 16GB).
>
> mmc1: new HS400 Enhanced strobe MMC card at address 0001
> mmcblk0: mmc1:0001 AJNB4R 14.6 GiB
> mmcblk0boot0: mmc1:0001 AJNB4R partition 1 4.00 MiB
> mmcblk0boot1: mmc1:0001 AJNB4R partition 2 4.00 MiB
> mmcblk0rpmb: mmc1:0001 AJNB4R partition 3 4.00 MiB
>
> Also I check this patchset with removing some caps to make sure
> all the init sequences for hs400/hs200/DDR52/HighSpeed are correct.
>
>
> Changes in v6:
> - add Doug's test-tag and Jaehoon's review-test-tag
> - add Doug's review-test-tag and Jaehoon's test-tag
> - a minor string assignment
>
> Changes in v5:
> - avoid to call hs400_enhanced+_strobe in mmc_set_initial_state
>   if no setting MMC_CAP2_HS400_ES.
> - add Adrian's ack for patch[5/5]
>
> Changes in v4:
> - check avail_type with EXT_CSD_CARD_TYPE_HS400 instead of
>   card_type
> - check if host support 8-bit when selecting hs400es
> - some minor fix suggested by Douglas and add his review tag
>
> Changes in v3:
> - remove helper function and shorten cap2 to MMC_CAP2_HS400_ES
> - rename callback to hs400_enhanced_strobe and make it return void
> - add enhanced_strobe in mmc_ios and pass it to hs400_enhanced_strobe
> - disable host's enhanced strobe in mmc_set_initial_state
> - remove bus checking after switching hs400es
> - add new function for hs400es timing selection
> - fix wrong judgement of mmc_card_hs400es
>
> Changes in v2:
> - switch to HS400ES from Highspeed mode directly
>
> Shawn Lin (5):
>   Documentation: mmc: add mmc-hs400-enhanced-strobe
>   mmc: core: add mmc-hs400-enhanced-strobe support
>   mmc: core: implement enhanced strobe support
>   mmc: debugfs: add HS400 enhanced strobe description
>   mmc: sdhci-of-arasan: implement enhanced strobe callback
>
>  Documentation/devicetree/bindings/mmc/mmc.txt |  1 +
>  drivers/mmc/core/bus.c                        |  3 +-
>  drivers/mmc/core/core.c                       |  9 +++
>  drivers/mmc/core/debugfs.c                    |  3 +-
>  drivers/mmc/core/host.c                       |  2 +
>  drivers/mmc/core/mmc.c                        | 84 ++++++++++++++++++++++++++-
>  drivers/mmc/host/sdhci-of-arasan.c            | 20 +++++++
>  include/linux/mmc/card.h                      |  1 +
>  include/linux/mmc/host.h                      | 12 ++++
>  include/linux/mmc/mmc.h                       |  3 +
>  10 files changed, 134 insertions(+), 4 deletions(-)
>

Thanks! A very nice series and with lot's of folkz helping out
reviewing and testing, great!

Applied for next!

Kind regards
Uffe