[PATCH V2 0/7] support the cpts found on am335x devices

-----Original Message-----
From: Richard Cochran [mailto:richardcochran at gmail.com]
Sent: Wednesday, October 17, 2012 11:57 PM
To: N, Mugunthan V
Cc: netdev at vger.kernel.org; linux-arm-kernel at lists.infradead.org; David
Miller; Chemparathy, Cyril; Govindarajan, Sriramakrishnan
Subject: Re: [PATCH V2 0/7] support the cpts found on am335x devices

On Tue, Oct 16, 2012 at 11:11:29PM +0000, N, Mugunthan V wrote:

quoted

Yes, I do agree that driver handles it. As Half roll over and Full

roll

quoted

over events are not handled in the driver, I am just curious how will
the misaligned TS would be handled and also in cpts set time, the

Lower

quoted

32 bit time is written to CPTS counter

#include <linux/clocksource.h>

I think the timecounter_init initializes only the software. But still I am
not clear how the time given in cpts_ptp_settime will be projected to
hardware. Can you correct me if I am wrong.

quoted

Since we poll for the 32bit over flow for every HZ * 8 cycle, won't
there be a system overhead. If the CPTS ref clock is changed

according

quoted

to the ptp freq adjust api, how will the timecounter take care of

change

quoted

in frequency

There is nothing to do here. What are you asking?

I think instead of fixing the driver to AM335X, let's make the driver
generic as the same driver can be used to TI814X, TI813X and other
upcoming platforms TI811X where the CPTS ref clock can be changed as
per usage requirement.

quoted

The current driver which is in vanilla kernel doesn't use extended

slave

quoted

address which are conflict between TI814x CPSW IP version and AM335x

CPSW

quoted

IP version. I have just posted my version of CPTS implementation. May

be

quoted

we can work together make the driver compatible with both CPSW

versions

Okay.

quoted

Since CPSW is a 3port Switch we should not fix time stamping will be

enabled

quoted

only for slave 0 or passing slave number through DT. Its better if we
can configure both the slaves. This can be tested with EVM-sk which

has

quoted

both the slave ports pinned out.

I hope that you meant, "better if we can configure _either_ slave."
Considering how SO_TIMESTAMPING works, you can't use both at once.

Since CPSW as a Ethernet switch, the PTP packet can be delivered to
any downstream port. So if we fix the PTP time stamping to one port
then the driver won't receive time stamping information when the packet
is delivered to the other port.

Regards
Mugunthan V N