linux-kernel - RE: [PATCH misc v2 2/2] misc: Add Renesas Synchronization Management Unit (SMU) support

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Date:   Thu, 16 Sep 2021 15:33:06 +0000
From:   Min Li <min.li.xe@...esas.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "arnd@...db.de" <arnd@...db.de>,
        "derek.kiernan@...inx.com" <derek.kiernan@...inx.com>,
        "dragan.cvetic@...inx.com" <dragan.cvetic@...inx.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lee.jones@...aro.or" <lee.jones@...aro.or>
Subject: RE: [PATCH misc v2 2/2] misc: Add Renesas Synchronization Management
 Unit (SMU) support



> -----Original Message-----
> From: Greg KH <gregkh@...uxfoundation.org>
> Sent: September 16, 2021 1:26 AM
> To: Min Li <min.li.xe@...esas.com>
> Cc: arnd@...db.de; derek.kiernan@...inx.com; dragan.cvetic@...inx.com;
> linux-kernel@...r.kernel.org; lee.jones@...aro.or
> Subject: Re: [PATCH misc v2 2/2] misc: Add Renesas Synchronization
> Management Unit (SMU) support
> 
> On Wed, Sep 15, 2021 at 02:47:09PM -0400, min.li.xe@...esas.com wrote:
> > From: Min Li <min.li.xe@...esas.com>
> >
> > This driver is developed for the IDT ClockMatrix(TM) and 82P33xxx
> > families of timing and synchronization devices.It will be used by
> > Renesas PTP Clock Manager for Linux (pcm4l) software to provide
> > support to GNSS assisted partial timing support (APTS) and other
> networking timing functions.
> 
> Where is that software?

https://www.renesas.com/us/en/software-tool/ptp-clock-manager-linux

> 
> Why is this new api not a standard one?
> 

There is no actual standard for the GNSS assisted partial timing support (APTS)
In terms of Linux kernel API

> What is the standard here?
> 
> What do other devices do and why is this a new api?
> 

There is really no standard for APTS and different company has its own hw/sw solutions

> > Current version provides kernel API's to support the following
> > functions -set combomode to enable SYNCE clock support -read dpll's
> > state to determine if the dpll is locked to the GNSS channel -read
> > dpll's ffo (fractional frequency offset) in ppqt
> 
> Why do all of these have to be in the kernel at all?
> 

Because all these API's need spi/i2c accesses to the RSMU card and spi/i2c accesses have been
abstracted to the MFD driver in kernel

> thanks,
> 
> greg k-h