Messages in this thread | | | Date | Wed, 26 Feb 2020 00:50:40 +0100 | From | Andrew Lunn <> | Subject | Re: [RFC PATCH 0/2] AT8031 PHY timestamping support |
| |
On Wed, Feb 26, 2020 at 12:08:17AM +0100, Michael Walle wrote: > This patchset is the current state of my work for adding PHY timestamping > support. I just wanted to post this to the mailinglist before I never do > it. Maybe its a starting point for other people. That being said, I > wouldn't mind comments ;) The code basically works but there are three > major caveats: > > (1) The reading of timestamps via MDIO sometimes return wrong values. What > I see is that a part of the timestamp corresponds to the new timestamp > while another part still contains old values. Thus at the moment, I'm > reading the registers twice. I don't know if the reading actually > affects the update of the timestamp or the different timing (my MDIO > bus is rather slow, so reading the timestamp a second time take some > amount of time; but I've also tested with some delays and it didn't > had any effects). There is also no possibility to read the timestamp > atomically :(
Hi Michael
That sounds fundamentally broken. Which would be odd. Sometimes there is a way to take a snapshot of the value. Reading the first word could trigger this snapshot. Or the last word, or some status register. One would hope the datasheet would talk about this.
Andrew
| |