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

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:

quoted

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.

quoted

+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@kernel.org/ (local)
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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