linux-kernel - Re: [PATCH 0/6] mmc/memstick: rtsx

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Message-ID: <Pine.LNX.4.44L0.1610171234190.1586-100000@iolanthe.rowland.org>
Date:   Mon, 17 Oct 2016 12:34:56 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Ulf Hansson <ulf.hansson@...aro.org>
cc:     linux-mmc <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ritesh Raj Sarraf <rrs@...earchut.com>,
        Oliver Neukum <oneukum@...e.com>,
        USB list <linux-usb@...r.kernel.org>,
        Roger Tseng <rogerable@...ltek.com>,
        Wei WANG <wei_wang@...lsil.com.cn>
Subject: Re: [PATCH 0/6] mmc/memstick: rtsx_usb: Fix runtime PM issues

On Mon, 17 Oct 2016, Ulf Hansson wrote:

> On 13 October 2016 at 13:37, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> > The rtsx_usb_sdmmc (mmc/sd) and rtsx_usb_ms (memstick) devices are interfacing
> > an rtsx_usb device (managed by an mfd driver) while communicating with the
> > cards. The mmc/sd and memstick devices are children of the usb device.
> >
> > Issues has been reported [1] for rtsx, which have been investigated, discussed,
> > fixed, tested, etc, particularly when using mmc/sd cards. During the
> > investigation, some changes was proposed and tested successfully. In this
> > series I have picked up these changes and created some proper patches with
> > change-logs.
> >
> > It turned out that most of the problems was related to the runtime PM
> > deployment in the memstick and the mmc/sd driver, which are fixed in this
> > series.
> >
> > A couple of more issues were also discussed [2], which needs to be fixed as
> > well. Although they are out of scope for this series, so we will have to look
> > into those at a later point. Here's a brief summary of these leftovers:
> >
> > *)
> > It seems reasonable to turn off autosuspend for usb devices and instead rely on
> > the usb device's children to deal with autosuspend. The reason is simply that
> > the children has better knowledge of when using autosuspend makes sense.
> >
> > **)
> > Polling card detect mode is used both for mmc/sd and memstick. Because of the
> > lack of synchronization between the polling attempts for these subsystems, the
> > usb device may be powered on for unnecessary long intervals, thus we are
> > wasting power.
> >
> > Besides the above changes, I folded in a change in the mmc core which improves
> > the behaviour for mmc hosts using MMC_CAP2_NO_PRESCAN_POWERUP, which is the
> > case for the rtsx_usb_sdmmc driver.  This change should improve the boot time
> > with ~100ms per rtsx_usb_sdmmc device.
> >
> > Finally, as I couldn't find an active maintainer for the memstick
> > subsystem/driver and because the author of the drivers can be reached, I
> > volunteer to take this all through my mmc tree. Please tell me if that is
> > problem to any of you.
> >
> > [1]
> > https://www.spinics.net/lists/linux-usb/msg146998.html
> > [2]
> > https://www.spinics.net/lists/linux-mmc/msg39235.html
> >
> >
> > Alan Stern (1):
> >   memstick: rtsx_usb_ms: Runtime resume the device when polling for
> >     cards
> >
> > Ulf Hansson (5):
> >   mmc: rtsx_usb_sdmmc: Avoid keeping the device runtime resumed when
> >     unused
> >   mmc: rtsx_usb_sdmmc: Handle runtime PM while changing the led
> >   memstick: rtsx_usb_ms: Manage runtime PM when accessing the device
> >   mmc: rtsx_usb_sdmmc: Enable runtime PM autosuspend
> >   mmc: core: Don't power off the card when starting the host
> >
> >  drivers/memstick/host/rtsx_usb_ms.c |  6 ++++++
> >  drivers/mmc/core/core.c             |  9 ++++-----
> >  drivers/mmc/host/rtsx_usb_sdmmc.c   | 10 +++++-----
> >  3 files changed, 15 insertions(+), 10 deletions(-)
> >
> > --
> > 1.9.1
> >
> 
> Patch 1->4 applied for fixes. Holding patch 5->6 for a while, as they
> are intended for next!

Thanks for taking care of all these updates.

Alan Stern