linux-kernel - Re: [PATCH] mmc: renesas_sdhi_internal_dmac: Add MMC_CAP

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Date:   Thu, 14 Nov 2019 23:07:44 +0100
From:   Eugeniu Rosca <erosca@...adit-jv.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     Eugeniu Rosca <erosca@...adit-jv.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Niklas Söderlund <niklas.soderlund@...natech.se>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Simon Horman <horms+renesas@...ge.net.au>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Eugeniu Rosca <roscaeugeniu@...il.com>,
        Harish Jenny K N <harish_kandiga@...tor.com>,
        Andrew Gabbasov <andrew_gabbasov@...tor.com>
Subject: Re: [PATCH] mmc: renesas_sdhi_internal_dmac: Add MMC_CAP_ERASE to
 Gen3 SoCs

Hi Ulf,

On Thu, Nov 14, 2019 at 01:48:41PM +0100, Ulf Hansson wrote:

[..]
> 
> Let's first take a step back, because I don't know how the HW busy
> detection works for your controller.
> 
> I have noticed there is TMIO_STAT_CMD_BUSY bit being set for some
> variants, which seems to cause renesas_sdhi_wait_idle() to loop for a
> pre-defined number of loops/timeout. This looks scary, but I can't
> tell if it's really a problem.
> 
> BTW, do you know what TMIO_STAT_CMD_BUSY actually is monitoring?
> 
> I have also noticed that MMC_CAP_WAIT_WHILE_BUSY isn't set for any of
> the renesas/tmio variant hosts. Is that simply because the HW doesn't
> support this? Or because implementation is missing?

Hopefully Wolfram just addressed that?

> If you want to run a test that stretches the behaviour on the timeout
> path, I would rather use an SD-card (the older the better). For eMMCs
> the erase likely translates to a trim/discard, which is far more
> quicker than a real erase - as is what happens on an old SD card.

Running 'blkdiscard' with different SD cards on H3ULCB, I don't see any
signs of misbehavior:

root@...r-gen3:~# blkdiscard -V
blkdiscard from util-linux 2.32.1

root@...r-gen3:~# lsblk
NAME         MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
mmcblk0      179:0    0 59.2G  0 disk
mmcblk0boot0 179:8    0    4M  1 disk
mmcblk0boot1 179:16   0    4M  1 disk
mmcblk1      179:24   0   30G  0 disk

# Erasing 32 GiB uSD Card
root@...r-gen3:~# time blkdiscard -v /dev/mmcblk1
/dev/mmcblk1: Discarded 32227983360 bytes from the offset 0

real    0m1.198s
user    0m0.001s
sys     0m0.122s

# Erasing 64 GiB eMMC
root@...r-gen3:~# time blkdiscard -v /dev/mmcblk0
/dev/mmcblk0: Discarded 63585648640 bytes from the offset 0

real    0m8.703s
user    0m0.002s
sys     0m1.909s

I guess that by decreasing below erase sizes, I could further increase
the execution time, but these sysfs properties are read-only:

cat /sys/devices/platform/soc/ee100000.sd/mmc_host/mmc1/mmc1:59b4/preferred_erase_size
4194304
cat /sys/devices/platform/soc/ee100000.sd/mmc_host/mmc1/mmc1:59b4/erase_size
512

-- 
Best Regards,
Eugeniu