From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shawn Lin Subject: Re: [PATCH] mmc: Move the mmc driver init earlier Date: Tue, 12 Jun 2018 20:05:25 +0800 Message-ID: <03aa85b4-74cf-621c-08cf-271b4c0d8e8c@rock-chips.com> References: <20180608095154.22413-1-feng.tang@intel.com> <20180612084234.gjzq66xsqblryrkm@shbuild888> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Ulf Hansson Cc: Feng Tang , shawn.lin@rock-chips.com, Linux Kernel Mailing List , "linux-mmc@vger.kernel.org" , Greg Kroah-Hartman , Adrian Hunter List-Id: linux-mmc@vger.kernel.org On 2018/6/12 18:29, Ulf Hansson wrote: > On 12 June 2018 at 10:42, Feng Tang 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 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. > >> >>> >>>> >>>> Signed-off-by: Feng Tang >>>> --- >>>> 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. >> >> Do you mean the patch may break some platforms? Yes, I only tested on >> some IA based NUCs, and I did think about other architectures, things >> that may affect MMC are gpio/clk/pinctrl, and those are still earlier >> than mmc after change. > > I don't know if it breaks things, potentially it could, if drivers > don't implement support for -EPROBE_DEFER properly. > > However, more importantly, it's not real fix to the problem, just > something that seems to work for you. > > Kind regards > Uffe > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- Best Regards Shawn Lin