linux-kernel - Re: [PATCH 2/3] ARM: bus: da8xx-syscfg: new driver

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Message-ID: <2278105.geKhb8xoNC@avalon>
Date:   Wed, 19 Oct 2016 11:53:30 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Sekhar Nori <nsekhar@...com>, Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Russell King <linux@...linux.org.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        linux-drm <dri-devel@...ts.freedesktop.org>,
        linux-devicetree <devicetree@...r.kernel.org>,
        Jyri Sarha <jsarha@...com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH 2/3] ARM: bus: da8xx-syscfg: new driver

Hi Bartosz,

On Wednesday 19 Oct 2016 10:26:57 Bartosz Golaszewski wrote:
> 2016-10-18 22:49 GMT+02:00 Laurent Pinchart:
> > On Monday 17 Oct 2016 18:30:49 Bartosz Golaszewski wrote:
> >> Create the driver for the da8xx System Configuration and implement
> >> support for writing to the three Master Priority registers.
> >> 
> >> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> [snip]
> 
> >> +
> >> +Documentation:
> >> +OMAP-L138 (DA850) - http://www.ti.com/lit/ug/spruh82c/spruh82c.pdf
> >> +
> >> +Required properties:
> >> +
> >> +- compatible:                "ti,da850-syscfg"
> > 
> > Don't you need a reg property ?
> 
> Yes, Kevin already pointed that out. I'll add it in v2. Same for [1/3].
> 
> >> +Optional properties:
> >> +
> >> +The below properties are used to specify the priority of master
> >> peripherals.
> >> +They must be between 0-7 where 0 is the highest priority and 7 is the
> >> lowest.
> >> +
> >> +- ti,pri-arm-i:              ARM_I port priority.
> >> +
> >> +- ti,pri-arm-d:              ARM_D port priority.
> >> +
> >> +- ti,pri-upp:                uPP port priority.
> >> +
> >> +- ti,pri-sata:               SATA port priority.
> >> +
> >> +- ti,pri-pru0:               PRU0 port priority.
> >> +
> >> +- ti,pri-pru1:               PRU1 port priority.
> >> +
> >> +- ti,pri-edma30tc0:  EDMA3_0_TC0 port priority.
> >> +
> >> +- ti,pri-edma30tc1:  EDMA3_0_TC1 port priority.
> >> +
> >> +- ti,pri-edma31tc0:  EDMA3_1_TC0 port priority.
> >> +
> >> +- ti,pri-vpif-dma-0: VPIF DMA0 port priority.
> >> +
> >> +- ti,pri-vpif-dma-1: VPIF DMA1 port priority.
> >> +
> >> +- ti,pri-emac:               EMAC port priority.
> >> +
> >> +- ti,pri-usb0cfg:    USB0 CFG port priority.
> >> +
> >> +- ti,pri-usb0cdma:   USB0 CDMA port priority.
> >> +
> >> +- ti,pri-uhpi:               HPI port priority.
> >> +
> >> +- ti,pri-usb1:               USB1 port priority.
> >> +
> >> +- ti,pri-lcdc:               LCDC port priority.
> > 
> > I'm afraid this looks more like system configuration than hardware
> > description to me.
> 
> While you're certainly right, this approach is already implemented in
> several other memory and bus drivers and it was also suggested by
> Sekhar in one of the tilcdc rev1 threads. There's also no real
> alternative that I know of.

The fact that other drivers get it wrong is no excuse for copying them :-)

> > There was a BoF session about how to support this kind of performance
> > knobs at ELCE last week:
> > https://openiotelceurope2016.sched.org/event/7rss/bof-linux-device-perfor
> > mance-framework-michael-turquette-baylibre :-)
>
> I know, I was there. ;)

That's why I mentioned it :-)

> Unfortunately it was just a discussion about potential approaches -
> there's no code yet.

Patches are welcome ;-)

-- 
Regards,

Laurent Pinchart