linux-kernel - Re: [PATCH net-next v3 02/10] net: sparx5: add the basic sparx5 driver

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Date:   Mon, 07 Jun 2021 10:13:50 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Steen Hegelund <steen.hegelund@...rochip.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>, Russell King <linux@...linux.org.uk>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Mark Einon <mark.einon@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Simon Horman <simon.horman@...ronome.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>
Subject: Re: [PATCH net-next v3 02/10] net: sparx5: add the basic sparx5
 driver

On Mon, 2021-06-07 at 09:34 +0200, Steen Hegelund wrote:
> Hi Philipp,
> 
> Thanks for your comments.
> 
> On Fri, 2021-06-04 at 11:28 +0200, Philipp Zabel wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > Hi Steen,
> > 
> > On Fri, 2021-06-04 at 10:55 +0200, Steen Hegelund wrote:
> > > This adds the Sparx5 basic SwitchDev driver framework with IO range
> > > mapping, switch device detection and core clock configuration.
> > > 
> > > Support for ports, phylink, netdev, mactable etc. are in the following
> > > patches.
> > > 
> > > Signed-off-by: Steen Hegelund <steen.hegelund@...rochip.com>
> > > Signed-off-by: Bjarni Jonasson <bjarni.jonasson@...rochip.com>
> > > Signed-off-by: Lars Povlsen <lars.povlsen@...rochip.com>
> > > ---
> > >  drivers/net/ethernet/microchip/Kconfig        |    2 +
> > >  drivers/net/ethernet/microchip/Makefile       |    2 +
> > >  drivers/net/ethernet/microchip/sparx5/Kconfig |    9 +
> > >  .../net/ethernet/microchip/sparx5/Makefile    |    8 +
> > >  .../ethernet/microchip/sparx5/sparx5_main.c   |  746 +++
> > >  .../ethernet/microchip/sparx5/sparx5_main.h   |  273 +
> > >  .../microchip/sparx5/sparx5_main_regs.h       | 4642 +++++++++++++++++
> > >  7 files changed, 5682 insertions(+)
> > >  create mode 100644 drivers/net/ethernet/microchip/sparx5/Kconfig
> > >  create mode 100644 drivers/net/ethernet/microchip/sparx5/Makefile
> > >  create mode 100644 drivers/net/ethernet/microchip/sparx5/sparx5_main.c
> > >  create mode 100644 drivers/net/ethernet/microchip/sparx5/sparx5_main.h
> > >  create mode 100644 drivers/net/ethernet/microchip/sparx5/sparx5_main_regs.h
> > > 
> > [...]
> > > diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
> > > b/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
> > > new file mode 100644
> > > index 000000000000..73beb85bc52d
> > > --- /dev/null
> > > +++ b/drivers/net/ethernet/microchip/sparx5/sparx5_main.c
> > > @@ -0,0 +1,746 @@
> > [...]
> > > +static int mchp_sparx5_probe(struct platform_device *pdev)
> > > +{
> > [...]
> > > +
> > > +     sparx5->reset = devm_reset_control_get_shared(&pdev->dev, "switch");
> > > +     if (IS_ERR(sparx5->reset)) {
> > 
> > Could you use devm_reset_control_get_optional_shared() instead of
> > ignoring this error? That would just return NULL if there's no "switch"
> > reset specified in the device tree.
> 
> Yes.  That sounds like a good idea.  I assume that the devm_reset_control_get_optional_shared()
> would also return null if another driver has already performed the reset?

It returns the same (shared) reset control. But the following
reset_control_reset() [1] is a no-op if the control has already
triggered once.

If multiple drivers need to coordinate to trigger the reset more than
once (for example once after suspend/resume), both have to use
reset_control_rearm() [2].

[1] https://www.kernel.org/doc/html/latest/driver-api/reset.html#c.reset_control_reset
[2] https://www.kernel.org/doc/html/latest/driver-api/reset.html#c.reset_control_rearm

regards
Philipp