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    SubjectRe: [PATCH v2] wait while adding MMC host to ensure root mounts
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    On 22 March 2013 18:03, Chris Ball <cjb@laptop.org> wrote:
    > Hi Sergey,
    >
    > On Wed, Mar 13 2013, Sergey Yanovich wrote:
    >> MMC hosts are added asynchronously. We need to wait until detect returns to
    >> avoid failed root filesystem mounts.
    >> ---8<---
    >> VFS: Cannot open root device "mmcblk0p1" or unknown-block(0,0): error -6
    >> Please append a correct "root=" boot option; here are the available partitions:
    >> mmc0: host does not support reading read-only switch. assuming write-enable.
    >> 1f00 256 mtdblock0 (driver?)
    >> 1f01 256 mtdblock1 (driver?)
    >> 1f02 2560 mtdblock2 mmc0: new SDHC card at address b368
    >> (driver?)
    >> 1f03 29696 mtdblock3 (driver?)
    >> 1f04 16384 mtdblock4 mmcblk0: mmc0:b368 USD 3.72 GiB
    >> (driver?)
    >> mmcblk0: p1
    >> b300 3910656 mmcblk0 driver: mmcblk
    >> b301 3906560 mmcblk0p1 00000000-01
    >> Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
    >> ---8<---
    >>
    >> Signed-off-by: Sergey Yanovich <ynvich@gmail.com>
    >> ---
    >> changes for v2:
    >> - removed exporting as symbol is in the same file
    >>
    >> drivers/mmc/core/core.c | 1 +
    >> 1 file changed, 1 insertion(+)
    >>
    >> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
    >> index aaed768..7196888 100644
    >> --- a/drivers/mmc/core/core.c
    >> +++ b/drivers/mmc/core/core.c
    >> @@ -2225,6 +2225,7 @@ void mmc_start_host(struct mmc_host *host)
    >> host->rescan_disable = 0;
    >> mmc_power_up(host);
    >> mmc_detect_change(host, 0);
    >> + mmc_flush_scheduled_work();
    >> }
    >>
    >> void mmc_stop_host(struct mmc_host *host)
    >
    > Thanks, this looks okay to me, I've pushed it to mmc-next for 3.10.
    >
    > - Chris.
    > --
    > Chris Ball <cjb@laptop.org> <http://printf.net/>
    > One Laptop Per Child

    Hi Chris,

    I noticed you merged this. I thought the idea was to use the rootwait
    or rootdelay?

    Moreover, this patch will have bad impact on booting the kernel, since
    every host device that has scheduled a detect work from it's probe
    function will also wait for it to finish. Even if it is the boot
    device of not. If this is needed, I would prefer that a host cap is
    used.

    Kind regards
    Ulf Hansson


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