linux-kernel - Re: [PATCH RFC net-next 00/19] net: mvpp2: Add TX Flow Control support

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Date:   Sun, 10 Jan 2021 18:17:27 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     stefanc@...vell.com
Cc:     netdev@...r.kernel.org, thomas.petazzoni@...tlin.com,
        davem@...emloft.net, nadavh@...vell.com, ymarkman@...vell.com,
        linux-kernel@...r.kernel.org, kuba@...nel.org, mw@...ihalf.com,
        andrew@...n.ch, atenart@...nel.org
Subject: Re: [PATCH RFC net-next  00/19] net: mvpp2: Add TX Flow Control
 support

Hi,

On Sun, Jan 10, 2021 at 05:30:04PM +0200, stefanc@...vell.com wrote:
> Armada hardware has a pause generation mechanism in GOP (MAC).
> GOP has to generate flow control frames based on an indication
> programmed in Ports Control 0 Register. There is a bit per port.
> However assertion of the PortX Pause bits in the ports control 0 register
> only sends a one time pause. To complement the function the GOP has
> a mechanism to periodically send pause control messages based on periodic counters.
> This mechanism ensures that the pause is effective as long as the Appropriate PortX Pause
> is asserted.

Can you ensure that your commit messages are consistently wrapped?
Some lines are wrapped others aren't.

> Problem is that Packet Processor witch actually can drop packets due to lack of resources

Does the packet processor engage in magic or witchcraft? I suppose
some would argue that firmware does "magic"! However, I think you
mean "which". :)

> not connected to the GOP flow control generation mechanism.
> To solve this issue Armada has firmware running on CM3 CPU dedectated for Flow Control
> support. Firmware monitors Packet Processor resources and asserts XON/XOFF by writing
> to Ports Control 0 Register.

What is the minimum firmware version that supports this?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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