On Fri, 2015-01-09 at 16:42 +0900, Joonyoung Shim wrote: > Hi, > > On 01/09/2015 01:21 PM, Jaehoon Chung wrote: > > On 01/09/2015 08:23 AM, Sjoerd Simons wrote: > >> On Thu, 2015-01-08 at 14:44 +0900, Joonyoung Shim wrote: > >>> Some exynos boards require special handling of SD4_nRESET_OUT line for > >>> eMMC memory to perform complete reboot e.g. Odroid X2/U3/XU3 boards. > >>> > >>> This will support eMMC reset using DT from reset_misc of samsung common > >>> board file and each board files can support eMMC reset on non DT case. > >>> > >>> Signed-off-by: Joonyoung Shim <[email protected]> > >> > >>> diff --git a/doc/device-tree-bindings/exynos/emmc-reset.txt > >>> b/doc/device-tree-bindings/exynos/emmc-reset.txt > >>> new file mode 100644 > >>> index 0000000..e48e508 > >>> --- /dev/null > >>> +++ b/doc/device-tree-bindings/exynos/emmc-reset.txt > >>> @@ -0,0 +1,15 @@ > >>> +* Samsung eMMC reset > >>> + > >>> +Some exynos boards require special handling of SD4_nRESET_OUT line for > >>> eMMC > >>> +memory to perform complete reboot. > >> > >> Nitpick, on XU3 the line you apparently need to twiddle is > >> SD0_nRESET_OUT. > >> > > Then, i think it's better to omit "SD4_". > > >> Is this type of usage of this pin specific to the Odroid Exynos boards > >> or potentially on more boards? (Sorry for the simple questions, but my > >> exynos documentation just says the line exists not what its intended > >> usage is). > > > > In case of Exynos4, eMMC can be used with sdhci controller or dw-mmc > > controller. > > So Pin name should be used to SD0 or SD4. > > > > But Exynos5 is only supported the dw-mmc controller. > > (So eMMC is used pin-name as "SD0".) > > > > I can find only "SD_4_nRESET_OUT" from exynos4412 user manual and only > "SD_0__nRESET_OUT" from exynos5422 user manual. > > > Best Regards, > > Jaehoon Chung > >> > >> Fwiw, I did a quick check in the linux code and it doesn't seem to be > >> using those pins for currently for any boards. However my X2 does > >> successfully reset/reboot in u-boot and linux, so it seems optional > >> there. The XU3 does fail to reset itself, so it seems required for that > >> board. > >> > > I checked upstream u-boot and hardkernel u-boot and i found codes to > reset eMMC using gpio. > > upstream u-boot: reset_misc() of board/samsung/odroid/odroid.c > hardkernel u-boot: reset_cpu() of arch/arm/cpu/armv7/exynos/reset.c
Yeah u-boot does it, but linux upstream kernel does not. Hence wondering about the requirements. -- Sjoerd Simons <[email protected]> Collabora Ltd.
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