linux-kernel - Re: dmatest no longer works on ARC SDP with DW DMAC

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Date:	Wed, 10 Aug 2016 15:46:15 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Cc:	"vinod.koul@...el.com" <vinod.koul@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Eugeniy.Paltsev@...opsys.com" <Eugeniy.Paltsev@...opsys.com>,
	"Nelson.Pereira@...opsys.com" <Nelson.Pereira@...opsys.com>,
	"linux-snps-arc@...ts.infradead.org" 
	<linux-snps-arc@...ts.infradead.org>,
	"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>
Subject: Re: dmatest no longer works on ARC SDP with DW DMAC

On Wed, 2016-08-10 at 12:22 +0000, Alexey Brodkin wrote:
> Hi Andy,
> 
> On Wed, 2016-08-10 at 15:15 +0300, Andy Shevchenko wrote:
> > 
> > On Wed, 2016-08-10 at 11:06 +0000, Eugeniy Paltsev wrote:
> > > 
> > > 
> > > dmatest on ARC SDP with DW DMAC became broken after df5c7386
> > > ("dmaengine: dw: some Intel devices has no memcpy support") and
> > > 30cb2639 ("dmaengine: dw: don't override platform data with
> > > autocfg")
> > > commits.
> > > * After df5c7386 commit "DMA_MEMCPY" capability option doesn't
> > > get set correctly in platform driver version.
> > > * After 30cb2639 commit
> > > "data_width" and "nollp" parameters don't get set correctly in
> > > platform
> > > driver version.
> > > 
> > > This happens because in old driver version there are three
> > > sources 
> > > of parameters: pdata, device tree and autoconfig hardware
> > > registers. 
> > > Some parameters were read from pdata and others from autoconfig
> > > hardware registers. If pdata was absent some pdata structure 
> > > fields were filled with parameters from device tree. But 30cb2639
> > > commit disabled overriding pdata with autocfg, so if we use
> > > platform
> > > driver version without pdata some parameters will not be set.
> > 
> > Yes, that's correct behaviour right now. You have to provide
> > platform
> > code which registers device with all platform data provided.
> 
> But given autocfg registers exist in HW why don't we rely on their
> contents?

And how exactly we can get that mem2mem support is absent / broken by
some reason?

All those quirks (bool is_*) kinda semi-hardware related.

What we can do is to have two categories of properties: a) genuine
hardware properties, and b) quirks.

So, refactor the ->probe() function in a way that will still copy quirks
and other non-hardware properties from platform data, if provided, to
the driver internals.

> 
> > 
> > > 
> > > I'm wondering what would be the best way to fix this situation?
> > 
> > Ideally we have to switch to use built-in device properties
> > (drivers/base/property.c) and platform code in your case has to
> > provide
> > properties.
> 
> What do you mean saying "built-in device properties"?
> Setting pdata structure? In our particular case we use device tree
> for DW DMAC setup.

Providing device properties instead of platform data. Again see above.

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