netdev - Re: [PATCH v6 1/6] net: phy: at803x: Export at803x_debug_reg

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Message-ID: <20180511182502.y74wm6dmtf3dbcln@pburton-laptop>
Date:   Fri, 11 May 2018 11:25:02 -0700
From:   Paul Burton <paul.burton@...s.com>
To:     Andrew Lunn <andrew@...n.ch>, Darren Hart <dvhart@...ux.intel.com>
CC:     <netdev@...r.kernel.org>, <linux-mips@...ux-mips.org>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH v6 1/6] net: phy: at803x: Export at803x_debug_reg_mask()

Hi Andrew,

On Fri, May 11, 2018 at 02:26:19AM +0200, Andrew Lunn wrote:
> On Thu, May 10, 2018 at 04:16:52PM -0700, Paul Burton wrote:
> > From: Andrew Lunn <andrew@...n.ch>
> > 
> > On some boards, this PHY has a problem when it hibernates. Export this
> > function to a board can register a PHY fixup to disable hibernation.
> 
> What do you know about the problem?
> 
> https://patchwork.ozlabs.org/patch/686371/
> 
> I don't remember how it was solved, but you should probably do the
> same.
> 
> 	Andrew

I'm afraid I don't know much about the problem - this one is your patch
entirely unchanged, and I don't have access to the hardware in question
(my board uses a Realtek RTL8211E PHY).

I presume you did this because the pch_gbe driver as-is in mainline
disables hibernation for the AR803X PHY found on the MinnowBoard, so
this would be preserving the existing behaviour of the driver?

That behaviour was introduced by commit f1a26fdf5944f ("pch_gbe: Add
MinnowBoard support"), so perhaps Darren as its author might know more?

My presumption would be that this is done to ensure that the PHY is
always providing the RX clock, which the EG20T manual says is required
for the MAC reset register RX_RST & ALL_RST bits to clear. We wait for
those using the call to pch_gbe_wait_clr_bit() in
pch_gbe_mac_reset_hw(), which happens before we initialize the PHY.

I could reorder the probe function a little to initialize the PHY before
performing the MAC reset, drop this patch and the AR803X hibernation
stuff from patch 2 if you like. But again, I can't actually test the
result on the affected hardware.

Thanks,
    Paul