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SubjectRe: [PATCH] mmc: Move the mmc driver init earlier
On 8 June 2018 at 11:51, Feng Tang <feng.tang@intel.com> wrote:
> When doing some boot time optimization for an eMMC rootfs NUCs,
> we found the rootfs may spend around 100 microseconds waiting
> for eMMC card to be initialized, then the rootfs could be
> mounted.
> [ 1.216561] Waiting for root device /dev/mmcblk1p1...
> [ 1.289262] mmc1: new HS400 MMC card at address 0001
> [ 1.289667] mmcblk1: mmc1:0001 R1J56L 14.7 GiB
> [ 1.289772] mmcblk1boot0: mmc1:0001 R1J56L partition 1 8.00 MiB
> [ 1.289869] mmcblk1boot1: mmc1:0001 R1J56L partition 2 8.00 MiB
> [ 1.289967] mmcblk1rpmb: mmc1:0001 R1J56L partition 3 4.00 MiB
> [ 1.292798] mmcblk1: p1 p2 p3
> [ 1.300576] EXT4-fs (mmcblk1p1): couldn't mount as ext3 due to feature incompatibilities
> [ 1.300912] EXT4-fs (mmcblk1p1): couldn't mount as ext2 due to feature incompatibilities
>
> And this is a common problem for smartphones, tablets, embedded
> devices and automotive products. This patch will make the eMMC/SD
> card start initializing earlier, by changing its order in drivers/Makefile.
>
> On our platform, the waiting for eMMC card is almost eliminated with the patch,
> which is critical to boot time.

I am wondering what kernel version you are running here. There have
been some changes to the mmc initialization path, which perhaps can
help.

>
> Signed-off-by: Feng Tang <feng.tang@intel.com>
> ---
> drivers/Makefile | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/Makefile b/drivers/Makefile
> index 24cd47014657..c473afd3c688 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -50,6 +50,9 @@ obj-$(CONFIG_REGULATOR) += regulator/
> # reset controllers early, since gpu drivers might rely on them to initialize
> obj-$(CONFIG_RESET_CONTROLLER) += reset/
>
> +# put mmc early as many morden devices use emm/sd card as rootfs storage
> +obj-y += mmc/
> +

Your suggested approach isn't really a solution, as it may work for
your particular case but not for everybody else.

> # tty/ comes before char/ so that the VT console is the boot-time
> # default.
> obj-y += tty/
> @@ -128,7 +131,6 @@ obj-$(CONFIG_EISA) += eisa/
> obj-$(CONFIG_PM_OPP) += opp/
> obj-$(CONFIG_CPU_FREQ) += cpufreq/
> obj-$(CONFIG_CPU_IDLE) += cpuidle/
> -obj-y += mmc/
> obj-$(CONFIG_MEMSTICK) += memstick/
> obj-$(CONFIG_NEW_LEDS) += leds/
> obj-$(CONFIG_INFINIBAND) += infiniband/
> --
> 2.14.1
>

Kind regards
Uffe

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