linux-kernel - Re: [PATCH v5 2/2] DW DMAC: add multi-block property to device tree

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Message-ID: <1480074030.2534.46.camel@synopsys.com>
Date:   Fri, 25 Nov 2016 11:40:31 +0000
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>
CC:     "vinod.koul@...el.com" <vinod.koul@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "shiraz.linux.kernel@...il.com" <shiraz.linux.kernel@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "vireshk@...nel.org" <vireshk@...nel.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "christian.ruppert@...tech.com" <christian.ruppert@...tech.com>,
        "arnd@...db.de" <arnd@...db.de>
Subject: Re: [PATCH v5 2/2] DW DMAC: add multi-block property to device tree

On Thu, 2016-11-24 at 17:58 +0200, Andy Shevchenko wrote:
> On Thu, 2016-11-24 at 17:52 +0200, Andy Shevchenko wrote:
> > 
> > On Thu, 2016-11-24 at 18:04 +0300, Eugeniy Paltsev wrote:
> > > 
> > > Several versions of DW DMAC have multi block transfers hardware
> > > support. Hardware support of multi block transfers is disabled
> > > by default if we use DT to configure DMAC and software emulation
> > > of multi block transfers used instead.
> > > Add multi-block property, so it is possible to enable hardware
> > > multi block transfers (if present) via DT.
> > > 
> > > Switch from per device is_nollp variable to multi_block array
> > > to be able enable/disable multi block transfers separately per
> > > channel.
> > Thanks for an update. Basically I'm fine with this one.
> > 
> > So, we still have question about autoconfiguration in SPEAr SoCs,
> > and
> > your ARC SoC but it's a different story. I would expect once you
> > will
> > clarify it.
> > 
> > Another one is minor listed below, otherwise
> > 
> > Acked-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > 
> > > 
> > > @@ -152,6 +154,11 @@ dw_dma_parse_dt(struct platform_device
> > > *pdev)
> > >  			pdata->data_width[tmp] = BIT(arr[tmp] &
> > > 0x07);
> > >  	}
> > >  
> > > +	if (!of_property_read_u32_array(np, "multi-block", chan,
> > > nr_channels)) {
> > > +		for (tmp = 0; tmp < nr_channels; tmp++)
> > > +			pdata->multi_block[tmp] = chan[tmp];
> > ...mb (as short of multi-block) would suit better.
> Oh, sorry, guys, but one more important thing. If there is no such
> property, keep a default to "supported". Otherwise you will break old
> (working) DTBs.
Should I remove explicit declaration "multi-block" property from
existing DTS (which I added during v5 patch iteration)?

I mean that:
---------------------->8-----------------------
+			multi-block = <1 1 1 1 1 1 1 1>;
---------------------->8-----------------------

We don't actually need it, if we use use 1 ("supported") as "multi-
block" property default value.

-- 
 Paltsev Eugeniy