linux-kernel - Re: [PATCH v3 07/12] net: ll_temac: Support indirect

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Date:   Tue, 30 Apr 2019 18:59:31 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Esben Haabendal <esben@...nix.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Michal Simek <michal.simek@...inx.com>,
        YueHaibing <yuehaibing@...wei.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Yang Wei <yang.wei9@....com.cn>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 07/12] net: ll_temac: Support indirect_mutex share
 within TEMAC IP

On Tue, Apr 30, 2019 at 09:17:54AM +0200, Esben Haabendal wrote:
> Indirect register access goes through a DCR bus bridge, which
> allows only one outstanding transaction.  And to make matters
> worse, each TEMAC IP block contains two Ethernet interfaces, and
> although they seem to have separate registers for indirect access,
> they actually share the registers.  Or to be more specific, MSW, LSW
> and CTL registers are physically shared between Ethernet interfaces
> in same TEMAC IP, with RDY register being (almost) specificic to
> the Ethernet interface.  The 0x10000 bit in RDY reflects combined
> bus ready state though.
> 
> So we need to take care to synchronize not only within a single
> device, but also between devices in same TEMAC IP.
> 
> This commit allows to do that with legacy platform devices.
> 
> For OF devices, the xlnx,compound parent of the temac node should be
> used to find siblings, and setup a shared indirect_mutex between them.
> I will leave this work to somebody else, as I don't have hardware to
> test that.  No regression is introduced by that, as before this commit
> using two Ethernet interfaces in same TEMAC block is simply broken.
> 
> Signed-off-by: Esben Haabendal <esben@...nix.com>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew