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

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Message-ID: <1480003098.20074.18.camel@linux.intel.com>
Date:   Thu, 24 Nov 2016 17:58:18 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        devicetree@...r.kernel.org
Cc:     robh+dt@...nel.org, mark.rutland@....com,
        linux-kernel@...r.kernel.org, vinod.koul@...el.com,
        dmaengine@...r.kernel.org, arnd@...db.de,
        linux-snps-arc@...ts.infradead.org, vireshk@...nel.org,
        shiraz.linux.kernel@...il.com, christian.ruppert@...tech.com
Subject: Re: [PATCH v5 2/2] DW DMAC: add multi-block property to device tree

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.

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy