netdev - Re: [PATCH net-next 0/3] ice: lighter locking for PTP time reading

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Message-ID: <83a3cc75-a8c8-446b-a083-0ef62134d850@intel.com>
Date: Mon, 26 Feb 2024 11:16:49 -0800
From: Jacob Keller <jacob.e.keller@...el.com>
To: Michal Schmidt <mschmidt@...hat.com>, <intel-wired-lan@...ts.osuosl.org>
CC: Jesse Brandeburg <jesse.brandeburg@...el.com>, Richard Cochran
	<richardcochran@...il.com>, Arkadiusz Kubalewski
	<arkadiusz.kubalewski@...el.com>, Karol Kolacinski
	<karol.kolacinski@...el.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 0/3] ice: lighter locking for PTP time reading



On 2/26/2024 7:11 AM, Michal Schmidt wrote:
> This series removes the use of the heavy-weight PTP hardware semaphore
> in the gettimex64 path. Instead, serialization of access to the time
> register is done using a host-side spinlock. The timer hardware is
> shared between PFs on the PCI adapter, so the spinlock must be shared
> between ice_pf instances too.
> 
> Michal Schmidt (3):
>   ice: add ice_adapter for shared data across PFs on the same NIC
>   ice: avoid the PTP hardware semaphore in gettimex64 path
>   ice: fold ice_ptp_read_time into ice_ptp_gettimex64
> 

Glad to see some fix and improvement in this place. I had been
considering switching the hardware semaphore entirely to be a shared
mutex instead, but this direction also seems reasonable and fixes most
of the issues. We could actually extend this to replace the semaphore
with a mutex in order to avoid the PCIe transactions required to handle
the hardware semaphore register.