On 12/17/2013 02:25 AM, Dong Aisheng wrote: > Hi Stephen, > > On Sat, Dec 14, 2013 at 6:43 AM, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: >> On one of my eMMC devices, I see the following results from calling >> mmc_do_calc_max_discard() with various parameters: >> >> [ 3.057263] MMC_DISCARD_ARG max_discard 1 >> [ 3.057266] MMC_ERASE_ARG max_discard 4096 >> [ 3.057267] MMC_TRIM_ARG max_discard 1 >> >> This causes mmc_calc_max_discard() to return 1, which makes the discard >> IOCTL extremely slow. >> > > IMX met the similar issue. > http://www.spinics.net/lists/linux-mmc/msg23375.html > It's caused by the max_discard_to supported by host is too small. > > I submitted the fix patches: > http://www.spinics.net/lists/arm-kernel/msg294924.html > Please see if it helps for you, especially patch #5. > It could increase the max_discard_to if Tegra has same problem. Thanks for the pointer! Yes, Tegra has SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK set, and has a max clock of 208MHz specified in HW, yet we only run the HW at 48MHz upstream, since we haven't actually implemented any of the advanced/faster transfer rates yet. Hence that patch does avoid/solve the issue on 2 of my boards. However, the patch doesn't solve the problem on 2 other boards, since the eMMC device on those boards specifies a much larger timeout, which still causes max_discard to be set to 0. It sounds like the real solution is what was discussed elsewhere in this thread; to use command polling for erases? Even on the boards where your patch solves the problem, isn't it just a temporary measure; as soon as we upstream the changes to enable the faster transfer modes, we'll have a faster SDCLK, and hence again be limited in the discard size, perhaps down to a single sector again. (Incidentally, I think the code should be limiting to a single erase block, not a single sector. I'll send a separate patch to fix that, and Cc everyone here). -- 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
