netdev - Re: [PATCH] net:cpsw: Pass unhandled ioctl's on to generic phy ioctl

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Message-ID: <1391550719.3003.33.camel@deadeye.wl.decadent.org.uk>
Date:	Tue, 04 Feb 2014 21:51:59 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Sørensen, Stefan 
	<Stefan.Sorensen@...ctralink.com>
Cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"mugunthanvnm@...com" <mugunthanvnm@...com>
Subject: Re: [PATCH] net:cpsw: Pass unhandled ioctl's on to generic phy ioctl

On Tue, 2014-02-04 at 15:08 +0000, Sørensen, Stefan wrote:
> On Tue, 2014-02-04 at 10:50 +0000, Ben Hutchings wrote:
> > > This patch allows the use of a generic timestamping phy connected
> > > to the cpsw if CPTS support is not enabled.
> > 
> > What if CPTS support is enabled in the driver, but this particular
> > machine doesn't have it and uses a timestamping PHY instead?
> 
> That would not work, the CPTS will grab the SIOC{G,S}HWTSTAMP. I'm not
> sure how that could be configured at runtime, other than a private
> ethtool flag.

Do all versions of CPSW include hardware timestamping?  Because the
condition at the top of cpsw_htstamp_ioctl() suggested to me that there
are some that don't.

> Also it seem as the situation with a timestamping MAC and a timestamping
> PHY could deliver bogus ethtool timestamping info, as it will come from
> the PHY if available, but the timestamping will be handled by the MAC.
[...]

Right.  If all versions of CPSW include hardware timestamping then
bother with PHY timestamping at all?  And why make CONFIG_TI_CPTS
configurable?

Ben.

-- 
Ben Hutchings
One of the nice things about standards is that there are so many of them.

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