From: Ulf Hansson <ulf.hansson@linaro.org>
To: Eugeniu Rosca <erosca@de.adit-jv.com>
Cc: "Wolfram Sang" <wsa@the-dreams.de>,
"Wolfram Sang" <wsa+renesas@sang-engineering.com>,
"Yoshihiro Shimoda" <yoshihiro.shimoda.uh@renesas.com>,
"Niklas Söderlund" <niklas.soderlund@ragnatech.se>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
"Simon Horman" <horms+renesas@verge.net.au>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
"Eugeniu Rosca" <roscaeugeniu@gmail.com>,
"Harish Jenny K N" <harish_kandiga@mentor.com>,
"Andrew Gabbasov" <andrew_gabbasov@mentor.com>
Subject: Re: [PATCH] mmc: renesas_sdhi_internal_dmac: Add MMC_CAP_ERASE to Gen3 SoCs
Date: Thu, 14 Nov 2019 13:48:41 +0100 [thread overview]
Message-ID: <CAPDyKFp5iqrFDM1EWnYBwFmQAiAA5FADDLAyuVVBgMu4Sx=x5w@mail.gmail.com> (raw)
In-Reply-To: <20191114113743.GA19656@vmlxhi-102.adit-jv.com>
On Thu, 14 Nov 2019 at 12:37, Eugeniu Rosca <erosca@de.adit-jv.com> wrote:
>
> Hi everyone,
>
> On Thu, Nov 14, 2019 at 11:56:23AM +0100, Ulf Hansson wrote:
> > On Tue, 12 Nov 2019 at 21:49, Wolfram Sang <wsa@the-dreams.de> wrote:
> > >
> > > On Tue, Nov 12, 2019 at 02:48:08PM +0100, Eugeniu Rosca wrote:
> > > > From: Harish Jenny K N <harish_kandiga@mentor.com>
> > > >
> > > > Enable MMC_CAP_ERASE capability in the driver to allow
> > > > erase/discard/trim requests.
> > > >
> > > > Suggested-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>
> > > > Signed-off-by: Harish Jenny K N <harish_kandiga@mentor.com>
> > > > [erosca: Forward-port and test on v5.4-rc7 using H3ULCB-KF:
> > > > "blkdiscard /dev/mmcblk0" passes with this patch applied
> > > > and complains otherwise:
> > > > "BLKDISCARD ioctl failed: Operation not supported"]
> > > > Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
> > >
> > > Looks good to me. Just a generic question, probably more for Ulf:
> > >
> > > Why does this CAP_ERASE exist? As I understand, the driver only needs to
> > > set the flag and no further handling is required. Why would a driver not
> > > set this flag and not support erase/trim commands?
> >
> > I am working on removing the cap, altogether. Step by step, this is
> > getting closer now.
> >
> > The main problem has been about busy detect timeouts, as an erase
> > command may have a very long busy timeout. On the host side, they
> > typically need to respect the cmd->busy_timeout for the request, and
> > if it can't because of some HW limitation, it needs to set
> > mmc->max_busy_timeout.
>
> FWIW we've discussed such concerns internally, based on past commits
> which either disable [1-2] busy timeouts or increase their value [3].
>
> To get a feeling if this is relevant for R-Car3, I've run blkdiscard on
> a 64 GiB eMMC without noticing any issues on v5.4-rc7. Hopefully this
> is sufficient as testing?
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?
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.
>
> >
> > Once that is fixed for all, we can drop CAP_ERASE.
> >
> > Kind regards
> > Uffe
>
> [1] 93caf8e69eac76 ("omap_hsmmc: add erase capability")
> [2] b13d1f0f9ad64b ("mmc: omap: Add erase capability")
> [3] ec30f11e821f2d ("mmc: rtsx_usb: Use the provided busy timeout from the mmc core")
>
> --
> Best Regards,
> Eugeniu
Kind regards
Uffe
next prev parent reply other threads:[~2019-11-14 12:49 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-12 13:48 [PATCH] mmc: renesas_sdhi_internal_dmac: Add MMC_CAP_ERASE to Gen3 SoCs Eugeniu Rosca
2019-11-12 20:49 ` Wolfram Sang
2019-11-14 10:56 ` Ulf Hansson
2019-11-14 11:37 ` Eugeniu Rosca
2019-11-14 12:48 ` Ulf Hansson [this message]
2019-11-14 20:15 ` Wolfram Sang
2019-11-15 9:19 ` Ulf Hansson
2019-11-15 10:12 ` Wolfram Sang
2019-11-15 10:38 ` Ulf Hansson
2019-11-14 22:07 ` Eugeniu Rosca
2019-11-15 9:27 ` Ulf Hansson
2019-11-15 12:51 ` Eugeniu Rosca
2019-11-15 13:54 ` Eugeniu Rosca
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