netdev - Re: [PATCH net v2 2/9] net: axienet: Wait for PhyRstCmplt after core reset

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Date:   Wed, 12 Jan 2022 20:15:52 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Robert Hancock <robert.hancock@...ian.com>
Cc:     netdev@...r.kernel.org, radhey.shyam.pandey@...inx.com,
        davem@...emloft.net, kuba@...nel.org,
        linux-arm-kernel@...ts.infradead.org, michal.simek@...inx.com,
        ariane.keller@....ee.ethz.ch, daniel@...earbox.net
Subject: Re: [PATCH net v2 2/9] net: axienet: Wait for PhyRstCmplt after core
 reset

On Wed, Jan 12, 2022 at 11:36:53AM -0600, Robert Hancock wrote:
> When resetting the device, wait for the PhyRstCmplt bit to be set
> in the interrupt status register before continuing initialization, to
> ensure that the core is actually ready. The MgtRdy bit could also be
> waited for, but unfortunately when using 7-series devices, the bit does
> not appear to work as documented (it seems to behave as some sort of
> link state indication and not just an indication the transceiver is
> ready) so it can't really be relied on.
> 
> Fixes: 8a3b7a252dca9 ("drivers/net/ethernet/xilinx: added Xilinx AXI Ethernet driver")
> Signed-off-by: Robert Hancock <robert.hancock@...ian.com>
> ---
>  drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> index f950342f6467..f425a8404a9b 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> @@ -516,6 +516,16 @@ static int __axienet_device_reset(struct axienet_local *lp)
>  		return ret;
>  	}
>  
> +	/* Wait for PhyRstCmplt bit to be set, indicating the PHY reset has finished */
> +	ret = read_poll_timeout(axienet_ior, value,
> +				value & XAE_INT_PHYRSTCMPLT_MASK,
> +				DELAY_OF_ONE_MILLISEC, 50000, false, lp,
> +				XAE_IS_OFFSET);
> +	if (ret) {
> +		dev_err(lp->dev, "%s: timeout waiting for PhyRstCmplt\n", __func__);
> +		return ret;
> +	}
> +

Is this bit guaranteed to be clear before you start waiting for it?

   Andrew