On Tue, Jun 12, 2018 at 08:05:25PM +0800, Shawn Lin wrote: > On 2018/6/12 18:29, Ulf Hansson wrote: > > On 12 June 2018 at 10:42, Feng Tang <feng.tang@xxxxxxxxx> wrote: > > > Hi Ulf, > > > > > > Thanks for the review. > > > > > > On Tue, Jun 12, 2018 at 08:25:44AM +0200, Ulf Hansson wrote: > > > > On 8 June 2018 at 11:51, Feng Tang <feng.tang@xxxxxxxxx> 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. > > > These logs in commit msg are based on kernel 4.14, and the patch is generated > > > against kernel 4.17. > > > > Right. So it's quite recent, even if lot's of changes have been made > > to the mmc core since then. > > > > A few things (old/new) that is important. > > 1) Check if your mmc host driver support MMC_CAP_WAIT_WHILE_BUSY. That > > should have some effect, avoiding unnecessary polling. > > > > 2) Since 4.18 rc1, you will be able to configure an over estimated > > "power on" delay (via DT as well). Look at commit > > 6d796c68cd15234a33a4bd2ef7231125fea2dc6c. > > Sorry to chime in. We could also reduce the "power on" delay via hosts' > ->set_ios() callback. > > > > > 3) If you use a DT based platform, I think what people do is to > > re-organize the order of device nodes, such that as many as possible > > -EPROBE_DEFER is avoided to be returned by drivers. This is also not a > > good solution, but the best we have at this moment. > > Also DT based platform is allowed to add no-sd and no-sdio for the eMMC > node, which could slighly help reduce the boot time. > You could refer to Documentation/devicetree/bindings/mmc/mmc.txt for > details. Thanks Shawn for your tips, we did simliar thing :) for no-sd and no-sdio, and even disabled SDHCI controller that has nothing connected. - Feng -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
