netdev - RE: [PATCH v3 0/2] net: stmmac: Enhanced addressing mode for DWMAC 4.10

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Message-ID: <BN8PR12MB3266F851B071629898BB775AD3870@BN8PR12MB3266.namprd12.prod.outlook.com>
Date:   Wed, 25 Sep 2019 10:44:53 +0000
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     David Miller <davem@...emloft.net>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>
CC:     "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...com" <alexandre.torgue@...com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "jonathanh@...dia.com" <jonathanh@...dia.com>,
        "bbiswas@...dia.com" <bbiswas@...dia.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: RE: [PATCH v3 0/2] net: stmmac: Enhanced addressing mode for DWMAC
 4.10

From: David Miller <davem@...emloft.net>
Date: Sep/24/2019, 20:45:08 (UTC+00:00)

> From: Thierry Reding <thierry.reding@...il.com>
> Date: Fri, 20 Sep 2019 19:00:34 +0200
> 
> > From: Thierry Reding <treding@...dia.com>
> > 
> > The DWMAC 4.10 supports the same enhanced addressing mode as later
> > generations. Parse this capability from the hardware feature registers
> > and set the EAME (Enhanced Addressing Mode Enable) bit when necessary.
> 
> This looks like an enhancement and/or optimization rather than a bug fix.

Agree.

> Also, you're now writing to the high 32-bits unconditionally, even when
> it will always be zero because of 32-bit addressing.  That looks like
> a step backwards to me.

Don't agree. As per previous discussions and as per my IP knowledge, if 
EAME is not enabled / not supported the register can still be written. 
This is not fast path and will not impact any remaining operation. Can 
you please explain what exactly is the concern about this ?

Anyway, this is an important feature for performance so I hope Thierry 
re-submits this once -next opens and addressing the review comments.

---
Thanks,
Jose Miguel Abreu