netdev - Re: [PATCH v2 1/2] ptp/ptp_vmw: Implement PTP clock adjustments ops

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Message-ID: <CAD2QZ9bpLF6N1g0SwTx8xyJAc47=5LHyyfwWMeJeQWasZjTwbg@mail.gmail.com>
Date: Thu, 23 Oct 2025 10:38:22 +0530
From: Ajay Kaher <ajay.kaher@...adcom.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Cc: kuba@...nel.org, davem@...emloft.net, richardcochran@...il.com, 
	nick.shi@...adcom.com, alexey.makhalov@...adcom.com, andrew+netdev@...n.ch, 
	edumazet@...gle.com, pabeni@...hat.com, jiashengjiangcool@...il.com, 
	andrew@...n.ch, viswanathiyyappan@...il.com, wei.fang@....com, 
	rmk+kernel@...linux.org.uk, vladimir.oltean@....com, cjubran@...dia.com, 
	dtatulea@...dia.com, tariqt@...dia.com, netdev@...r.kernel.org, 
	bcm-kernel-feedback-list@...adcom.com, linux-kernel@...r.kernel.org, 
	florian.fainelli@...adcom.com, vamsi-krishna.brahmajosyula@...adcom.com, 
	tapas.kundu@...adcom.com, shubham-sg.gupta@...adcom.com, 
	karen.wang@...adcom.com, hari-krishna.ginka@...adcom.com
Subject: Re: [PATCH v2 1/2] ptp/ptp_vmw: Implement PTP clock adjustments ops

On Thu, Oct 23, 2025 at 3:47 AM Vadim Fedorenko
<vadim.fedorenko@...ux.dev> wrote:
>
> On 22/10/2025 18:27, Ajay Kaher wrote:
> > On Wed, Oct 22, 2025 at 4:43 PM Vadim Fedorenko
> > <vadim.fedorenko@...ux.dev> wrote:
> >>
> >> On 22/10/2025 11:51, Ajay Kaher wrote:
> >>> Implement PTP clock ops that set time and frequency of the underlying
> >>> clock. On supported versions of VMware precision clock virtual device,
> >>> new commands can adjust its time and frequency, allowing time transfer
> >>> from a virtual machine to the underlying hypervisor.
> >>>
> >>> In case of error, vmware_hypercall doesn't return Linux defined errno,
> >>> converting it to -EIO.
> >>>
> >>> Cc: Shubham Gupta <shubham-sg.gupta@...adcom.com>
> >>> Cc: Nick Shi <nick.shi@...adcom.com>
> >>> Tested-by: Karen Wang <karen.wang@...adcom.com>
> >>> Tested-by: Hari Krishna Ginka <hari-krishna.ginka@...adcom.com>
> >>> Signed-off-by: Ajay Kaher <ajay.kaher@...adcom.com>
> >>> ---
> >>>    drivers/ptp/ptp_vmw.c | 39 +++++++++++++++++++++++++++++----------
> >>>    1 file changed, 29 insertions(+), 10 deletions(-)
> >>>
> >>> diff --git a/drivers/ptp/ptp_vmw.c b/drivers/ptp/ptp_vmw.c
> >>> index 20ab05c4d..7d117eee4 100644
> >>> --- a/drivers/ptp/ptp_vmw.c
> >>> +++ b/drivers/ptp/ptp_vmw.c
> >>> @@ -1,6 +1,7 @@
> >>>    // SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
> >>>    /*
> >>> - * Copyright (C) 2020 VMware, Inc., Palo Alto, CA., USA
> >>> + * Copyright (C) 2020-2023 VMware, Inc., Palo Alto, CA., USA
> >>> + * Copyright (C) 2024-2025 Broadcom Ltd.
> >>>     *
> >>>     * PTP clock driver for VMware precision clock virtual device.
> >>>     */
> >>> @@ -16,20 +17,36 @@
> >>>
> >>>    #define VMWARE_CMD_PCLK(nr) ((nr << 16) | 97)
> >>>    #define VMWARE_CMD_PCLK_GETTIME VMWARE_CMD_PCLK(0)
> >>> +#define VMWARE_CMD_PCLK_SETTIME VMWARE_CMD_PCLK(1)
> >>> +#define VMWARE_CMD_PCLK_ADJTIME VMWARE_CMD_PCLK(2)
> >>> +#define VMWARE_CMD_PCLK_ADJFREQ VMWARE_CMD_PCLK(3)
> >>>
> >>>    static struct acpi_device *ptp_vmw_acpi_device;
> >>>    static struct ptp_clock *ptp_vmw_clock;
> >>>
> >>> +/*
> >>> + * Helpers for reading and writing to precision clock device.
> >>> + */
> >>>
> >>> -static int ptp_vmw_pclk_read(u64 *ns)
> >>> +static int ptp_vmw_pclk_read(int cmd, u64 *ns)
> >>>    {
> >>>        u32 ret, nsec_hi, nsec_lo;
> >>>
> >>> -     ret = vmware_hypercall3(VMWARE_CMD_PCLK_GETTIME, 0,
> >>> -                             &nsec_hi, &nsec_lo);
> >>> +     ret = vmware_hypercall3(cmd, 0, &nsec_hi, &nsec_lo);
> >>>        if (ret == 0)
> >>>                *ns = ((u64)nsec_hi << 32) | nsec_lo;
> >>> -     return ret;
> >>> +
> >>> +     return ret != 0 ? -EIO : 0;
> >>> +}
> >>
> >> Why do you need to introduce this change? VMWARE_CMD_PCLK_GETTIME is
> >> the only command used in read() in both patches of this patchset.
> >>
> >
> > Vadim, thanks for looking into patches.
> >
> > I have added ptp_vmw_pclk_write() where cmd has been passed as argument.
> > Keeping the same format for ptp_vmw_pclk_read() as well, also may be useful
> > in future.
> >
> > Let me know if you think it's better to keep ptp_vmw_pclk_read() as it
> > is. I will
> > revert in v3.
>
> I do believe it's better to keep code as is until you have real use of
> new feature. And I'm not quite sure which command you can use to do
> another read?

Sure, I will revert the changes of ptp_vmw_pclk_read() in v3.

-Ajay

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