netdev - Re: [PATCH RFC net-next 00/23] net: phylink managed EEE support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z0XGl0caztvVarmZ@shell.armlinux.org.uk>
Date: Tue, 26 Nov 2024 13:01:11 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Bryan Whitehead <bryan.whitehead@...rochip.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Jakub Kicinski <kuba@...nel.org>, Jose Abreu <joabreu@...opsys.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com,
	Marcin Wojtas <marcin.s.wojtas@...il.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>, netdev@...r.kernel.org,
	Oleksij Rempel <o.rempel@...gutronix.de>,
	Paolo Abeni <pabeni@...hat.com>, UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH RFC net-next 00/23] net: phylink managed EEE support

On Tue, Nov 26, 2024 at 12:51:36PM +0000, Russell King (Oracle) wrote:
> Patch 11 adds phylink managed EEE support. Two new MAC APIs are added,
> to enable and disable LPI. The enable method is passed the LPI timer
> setting which it is expected to program into the hardware, and also a
> flag ehther the transmit clock should be stopped.
> 
>  *** There are open questions here. Eagle eyed reviewers will notice
>    pl->config->lpi_interfaces. There are MACs out there which only
>    support LPI signalling on a subset of their interface types. Phylib
>    doesn't understand this. I'm handling this at the moment by simply
>    not activating LPI at the MAC, but that leads to ethtool --show-eee
>    suggesting that EEE is active when it isn't.
>  *** Should we pass the phy_interface_t to these functions?
>  *** Should mac_enable_tx_lpi() be allowed to fail if the MAC doesn't
>    support the interface mode?

There is another point to raise here - should we have a "validate_eee"
method in struct phylink_mac_ops so that MAC drivers can validate
settings such as the tx_lpi_timer value can be programmed into the
hardware?

We do have the situation on Marvell platforms where the programmed
value depends on the MAC speed, and is only 8 bit, which makes
validating its value rather difficult - at 1G speeds, it's a
resolution of 1us so we can support up to 255us. At 100M speeds,
it's 10us, supporting up to 2.55ms. This makes it awkward to be able
to validate the set_eee() settings are sane for the hardware. Should
Marvell platforms instead implement a hrtimer above this? That sounds
a bit problematical to manage sanely.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!