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

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Message-ID:
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Date: Tue, 19 Nov 2024 05:46:34 +0000
From: Jacky Chou <jacky_chou@...eedtech.com>
To: Andrew Jeffery <andrew@...econstruct.com.au>, "andrew+netdev@...n.ch"
	<andrew+netdev@...n.ch>, "davem@...emloft.net" <davem@...emloft.net>,
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	<devicetree@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-aspeed@...ts.ozlabs.org"
	<linux-aspeed@...ts.ozlabs.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject:
 回覆: [net-next 3/3] net: mdio: aspeed: Add dummy read for fire control

Hi Andrew Jeffery,

Thank you for your reply.

> >         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.
> 

Agree.
When the bus is sometimes busy, it may cause the driver is unable to 
write the register to the MDIO controller immediately.
Therefore, add a dummy read to ensure the previous write command 
has arrived to the MDIO controller before polling MDIO controller status.
I will add more details in next version of the commit.

Thanks,
Jacky