Re: [PATCH net-next 2/3] net: macb: Added ZynqMP-specific initialization

[Robert Hancock <robert.hancock@calian.com>]

On Thu, 2022-01-13 at 15:44 +0530, Harini Katakam wrote:
> +Radhey
> 
> Hi Robert,
> 
> On Thu, Jan 13, 2022 at 2:46 PM Michal Simek <michal.simek@xilinx.com> wrote:
> > 
> > 
> > On 1/12/22 19:11, Robert Hancock wrote:
> > > 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@calian.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 (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;
> > > +             }
> > 
> > I was playing with it recently on u-boot side and device reset should
> > happen
> > between phy init and phy power on to finish calibration.
> > At least that's I was told and that's I use in u-boot driver.
> > 
> > Harini/Piyush: Please correct me if I am wrong.
> 
> Thanks for the patch.
> 
> GEM should definitely be reset once after the serdes init and power on is
> done.
> It can be held in reset and released after serdes init or reset with a 1-0
> after
> serdes init. Either should be fine but a reset before phy init may not work.
> I've added Radhey who worked on this recently and can add any further info.

Thanks for the feedback on this. I believe I pretty much arrived at the
sequence I had via trial and error when trying to get things to work and so it
might not quite be ideal. I've done some tests with moving the reset down to
after the PHY init and power on and that seems to work well, so if that's the
preferred sequence I can switch to that.

> 
> Regards,
> Harini
-- 
Robert Hancock
Senior Hardware Designer, Calian Advanced Technologies
www.calian.com