linux-kernel - Re: [net-next 3/3] net: mdio: aspeed: Add dummy read for fire control

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Message-ID: <b8986779-27eb-4b60-b180-24d84ca9a501@lunn.ch>
Date: Tue, 19 Nov 2024 02:52:11 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Andrew Jeffery <andrew@...econstruct.com.au>
Cc: Jacky Chou <jacky_chou@...eedtech.com>, andrew+netdev@...n.ch,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, joel@....id.au, hkallweit1@...il.com,
	linux@...linux.org.uk, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [net-next 3/3] net: mdio: aspeed: Add dummy read for fire control

On Tue, Nov 19, 2024 at 09:35:39AM +1030, Andrew Jeffery wrote:
> Hi Jacky,
> 
> On Mon, 2024-11-18 at 18:47 +0800, Jacky Chou wrote:
> > Add a dummy read to ensure triggering mdio controller before starting
> > polling the status of mdio controller.
> > 
> > Signed-off-by: Jacky Chou <jacky_chou@...eedtech.com>
> > ---
> >  drivers/net/mdio/mdio-aspeed.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/net/mdio/mdio-aspeed.c b/drivers/net/mdio/mdio-
> > aspeed.c
> > index 4d5a115baf85..feae30bc3e78 100644
> > --- a/drivers/net/mdio/mdio-aspeed.c
> > +++ b/drivers/net/mdio/mdio-aspeed.c
> > @@ -62,6 +62,8 @@ static int aspeed_mdio_op(struct mii_bus *bus, u8
> > st, u8 op, u8 phyad, u8 regad,
> >                 | FIELD_PREP(ASPEED_MDIO_DATA_MIIRDATA, data);
> >  
> >         iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
> > +       /* Add dummy read to ensure triggering mdio controller */
> > +       (void)ioread32(ctx->base + ASPEED_MDIO_CTRL);
> 
> Why do this when the same register is immediately read by
> readl_poll_timeout() below?
> 
> If there is a reason, I'd like some more explanation in the comment
> you've added, discussing the details of the problem it's solving when
> taking into account the readl_poll_timeout() call.

Also, is this a fix? Should it have a Fixes: tag? If so, it should not
be part of this series, assuming the older devices have the same
issue.

	Andrew