Re: [PATCH 5/5] bus: mhi: host: mhi_phc: Add support for PHC over MHI

[Manivannan Sadhasivam]

On Thu, Aug 21, 2025 at 06:02:47PM -0700, Jakub Kicinski wrote:
> On Mon, 18 Aug 2025 12:25:50 +0530 Krishna Chaitanya Chundru wrote:
> > This patch introduces the MHI PHC (PTP Hardware Clock) driver, which
> > registers a PTP (Precision Time Protocol) clock and communicates with
> > the MHI core to get the device side timestamps. These timestamps are
> > then exposed to the PTP subsystem, enabling precise time synchronization
> > between the host and the device.
> 
> > +static struct ptp_clock_info qcom_ptp_clock_info = {
> > +	.owner    = THIS_MODULE,
> > +	.gettimex64 =  qcom_ptp_gettimex64,
> > +};
> 
> Yet another device to device clock sync driver. Please see the
> discussion here:
> https://lore.kernel.org/all/20250815113814.5e135318@xxxxxxxxxx/
> I think we have a consensus within the community that we should 
> stop cramming random clocks into the PTP subsystem.
> 

I agree with you that this clock is not a PTP clock. Looking at the other
discussion you pointed out above, I guess it is the time to come up with a new
framework that exposes the device clock to the host.

But my worry is that the new framework will look a lot like PTP Hardware Clock
(PHC) (atleast for the clock part) and will end up supporting the same userspace
tooling like phc2sys.

- Mani

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