linux-kernel - Re: [PATCH] net: macb: Correct usage of MACB_CAPS_CLK_HW

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Message-ID: <20201223192441.GH3198262@lunn.ch>
Date:   Wed, 23 Dec 2020 20:24:41 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     nicolas.ferre@...rochip.com, claudiu.beznea@...rochip.com,
        davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: macb: Correct usage of MACB_CAPS_CLK_HW_CHG flag on
 Zynq

On Wed, Dec 23, 2020 at 06:41:44PM +0000, Charles Keepax wrote:
> A new flag MACB_CAPS_CLK_HW_CHG was added and all callers of
> macb_set_tx_clk were gated on the presence of this flag.
> 
> if (!bp->tx_clk || !(bp->caps & MACB_CAPS_CLK_HW_CHG))
> 
> However the flag was not added to anything other than the new
> sama7g5_gem, turning that function call into a no op for all other
> systems. This breaks the networking on Zynq.

I'm not sure this is the correct fix. I think the original patch might
be broken. Look at the commit message wording:

                                                      The patch adds a new
    capability so that macb_set_tx_clock() to not be called for IPs having
    this capability

So MACB_CAPS_CLK_HW_CHG disables something, not enables it. So i
suspect this if statement is wrong and needs fixing.

	Andrew