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From:   =?ISO-8859-1?Q?J=E9r=F4me?= Pouiller <jerome.pouiller@silabs.com>
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     linux-wireless <linux-wireless@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        driverdevel <devel@driverdev.osuosl.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S . Miller" <davem@davemloft.net>,
        DTML <devicetree@vger.kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        linux-mmc <linux-mmc@vger.kernel.org>,
        Pali =?ISO-8859-1?Q?Roh=E1r?= <pali@kernel.org>
Subject: Re: [PATCH v5 08/24] wfx: add bus_sdio.c
Date:   Tue, 23 Mar 2021 18:53:46 +0100
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Organization: Silicon Labs
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References: <20210315132501.441681-1-Jerome.Pouiller@silabs.com> <4503971.bAhddQ8uqO@pc-42> <CAPDyKFoXgV3m-rMKfjqRj91PNjOGaWg6odWG-EGdFKkL+dGWoA@mail.gmail.com>
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On Tuesday 23 March 2021 15:11:56 CET Ulf Hansson wrote:
> On Mon, 22 Mar 2021 at 18:14, J=E9r=F4me Pouiller <jerome.pouiller@silabs=
.com> wrote:
> > On Monday 22 March 2021 13:20:35 CET Ulf Hansson wrote:
> > > On Mon, 15 Mar 2021 at 14:25, Jerome Pouiller <Jerome.Pouiller@silabs=
.com> wrote:
> > > >
> > > > From: J=E9r=F4me Pouiller <jerome.pouiller@silabs.com>
> > > >
> > > > Signed-off-by: J=E9r=F4me Pouiller <jerome.pouiller@silabs.com>
> > > > ---
> > > >  drivers/net/wireless/silabs/wfx/bus_sdio.c | 259 +++++++++++++++++=
++++
> > > >  1 file changed, 259 insertions(+)
> > > >  create mode 100644 drivers/net/wireless/silabs/wfx/bus_sdio.c
> > >
> > > [...]
> > >
> > > > +static const struct sdio_device_id wfx_sdio_ids[] =3D {
> > > > +       { SDIO_DEVICE(SDIO_VENDOR_ID_SILABS, SDIO_DEVICE_ID_SILABS_=
WF200) },
> > > > +       { },
> > > > +};
> > > > +MODULE_DEVICE_TABLE(sdio, wfx_sdio_ids);
> > > > +
> > > > +struct sdio_driver wfx_sdio_driver =3D {
> > > > +       .name =3D "wfx-sdio",
> > > > +       .id_table =3D wfx_sdio_ids,
> > > > +       .probe =3D wfx_sdio_probe,
> > > > +       .remove =3D wfx_sdio_remove,
> > > > +       .drv =3D {
> > > > +               .owner =3D THIS_MODULE,
> > > > +               .of_match_table =3D wfx_sdio_of_match,
> > >
> > > It's not mandatory to support power management, like system
> > > suspend/resume. However, as this looks like this is a driver for an
> > > embedded SDIO device, you probably want this.
> > >
> > > If that is the case, please assign the dev_pm_ops here and implement
> > > the ->suspend|resume() callbacks.
> >
> > I have no platform to test suspend/resume, so I have only a
> > theoretical understanding of this subject.
>=20
> I see.
>=20
> >
> > I understanding is that with the current implementation, the
> > device will be powered off on suspend and then totally reset
> > (including reloading of the firmware) on resume. I am wrong?
>=20
> You are correct, for a *removable* SDIO card. In this case, the
> mmc/sdio core will remove the corresponding SDIO card/device and its
> corresponding SDIO func devices at system suspend. It will then be
> redetected at system resume (and the SDIO func driver re-probed).
>=20
> Although, as this is an embedded SDIO device, per definition it's not
> a removable card (MMC_CAP_NONREMOVABLE should be set for the
> corresponding mmc host), the SDIO card will stick around and instead
> the ->suspend|resume() callback needs to be implemented for the SDIO
> func driver.

If I follow what has been done in other drivers I would write something
like:

  static int wfx_sdio_suspend(struct device *dev)
  {
          struct sdio_func *func =3D dev_to_sdio_func(dev);
          struct wfx_sdio_priv *bus =3D sdio_get_drvdata(func);

          config_reg_write_bits(bus->core, CFG_IRQ_ENABLE_DATA, 0);
          // Necessary to keep device firmware in RAM
          return sdio_set_host_pm_flags(func, MMC_PM_KEEP_POWER);
  }

However, why not the implementation below?

  static int wfx_sdio_suspend(struct device *dev)
  {
          struct sdio_func *func =3D dev_to_sdio_func(dev);

          wfx_sdio_remove(func);
          return 0;
  }

In both cases, I worry to provide these functions without being able to
test them.


--=20
J=E9r=F4me Pouiller