Date:   Thu, 13 Jan 2022 16:32:47 +0000
From:   Robert Hancock <robert.hancock@...ian.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Claudiu.Beznea@...rochip.com" <Claudiu.Beznea@...rochip.com>
CC:     "Nicolas.Ferre@...rochip.com" <Nicolas.Ferre@...rochip.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH net-next 2/3] net: macb: Added ZynqMP-specific
 initialization

On Thu, 2022-01-13 at 08:04 +0000, Claudiu.Beznea@...rochip.com wrote:
> On 12.01.2022 20:11, Robert Hancock wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the
> > content is safe
> > 
> > The GEM controllers on ZynqMP were missing some initialization steps which
> > are required in some cases when using SGMII mode, which uses the PS-GTR
> > transceivers managed by the phy-zynqmp driver.
> > 
> > The GEM core appears to need a hardware-level reset in order to work
> > properly in SGMII mode in cases where the GT reference clock was not
> > present at initial power-on. This can be done using a reset mapped to
> > the zynqmp-reset driver in the device tree.
> > 
> > Also, when in SGMII mode, the GEM driver needs to ensure the PHY is
> > initialized and powered on when it is initializing.
> > 
> > Signed-off-by: Robert Hancock <robert.hancock@...ian.com>
> > ---
> >  drivers/net/ethernet/cadence/macb_main.c | 47 +++++++++++++++++++++++-
> >  1 file changed, 46 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/cadence/macb_main.c
> > b/drivers/net/ethernet/cadence/macb_main.c
> > index a363da928e8b..65b0360c487a 100644
> > --- a/drivers/net/ethernet/cadence/macb_main.c
> > +++ b/drivers/net/ethernet/cadence/macb_main.c
> > @@ -34,7 +34,9 @@
> >  #include <linux/udp.h>
> >  #include <linux/tcp.h>
> >  #include <linux/iopoll.h>
> > +#include <linux/phy/phy.h>
> >  #include <linux/pm_runtime.h>
> > +#include <linux/reset.h>
> >  #include "macb.h"
> > 
> >  /* This structure is only used for MACB on SiFive FU540 devices */
> > @@ -4455,6 +4457,49 @@ static int fu540_c000_init(struct platform_device
> > *pdev)
> >         return macb_init(pdev);
> >  }
> > 
> > +static int zynqmp_init(struct platform_device *pdev)
> > +{
> > +       struct net_device *dev = platform_get_drvdata(pdev);
> > +       struct macb *bp = netdev_priv(dev);
> > +       int ret;
> > +
> > +       /* Fully reset GEM controller at hardware level using zynqmp-reset
> > driver,
> > +        * if mapped in device tree.
> > +        */
> > +       ret = device_reset(&pdev->dev);
> > +       if (ret) {
> > +               dev_err_probe(&pdev->dev, ret, "failed to reset
> > controller");
> > +               return ret;
> 
> If using old device trees this will fail, right? If yes, you should take
> care this code will also work with old device trees.

I think I had believed device_reset should just return a success without doing
anything if the device tree has no reset defined for the device, but it appears
to get that behavior we should be using device_reset_optional.

> 
> Thank you,
> Claudiu Beznea
> 
> > +       }
> > +
> > +       if (bp->phy_interface == PHY_INTERFACE_MODE_SGMII) {
> > +               /* Ensure PS-GTR PHY device used in SGMII mode is ready */
> > +               struct phy *sgmii_phy = devm_phy_get(&pdev->dev, "sgmii-
> > phy");
> > +
> > +               if (IS_ERR(sgmii_phy)) {
> > +                       ret = PTR_ERR(sgmii_phy);
> > +                       dev_err_probe(&pdev->dev, ret,
> > +                                     "failed to get PS-GTR PHY\n");
> > +                       return ret;
> > +               }
> > +
> > +               ret = phy_init(sgmii_phy);
> > +               if (ret) {
> > +                       dev_err(&pdev->dev, "failed to init PS-GTR PHY:
> > %d\n",
> > +                               ret);
> > +                       return ret;
> > +               }
> > +
> > +               ret = phy_power_on(sgmii_phy);
> > +               if (ret) {
> > +                       dev_err(&pdev->dev, "failed to power on PS-GTR PHY:
> > %d\n",
> > +                               ret);
> > +                       return ret;
> > +               }
> > +       }
> > +       return macb_init(pdev);
> > +}
> > +
> >  static const struct macb_usrio_config sama7g5_usrio = {
> >         .mii = 0,
> >         .rmii = 1,
> > @@ -4550,7 +4595,7 @@ static const struct macb_config zynqmp_config = {
> >                         MACB_CAPS_GEM_HAS_PTP | MACB_CAPS_BD_RD_PREFETCH,
> >         .dma_burst_length = 16,
> >         .clk_init = macb_clk_init,
> > -       .init = macb_init,
> > +       .init = zynqmp_init,
> >         .jumbo_max_len = 10240,
> >         .usrio = &macb_default_usrio,
> >  };
> > --
> > 2.31.1
> > 

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