linux-kernel - RE: [PATCH v3 07/12] usb: chipidea: add a usb2 driver for ci13xxx

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Message-ID: <cd73d8a384cc4040a0bbc6afc1f3063d@DM2PR0301MB0783.namprd03.prod.outlook.com>
Date:	Wed, 16 Jul 2014 11:58:14 +0000
From:	Peter Chen <Peter.Chen@...escale.com>
To:	Arnd Bergmann <arnd@...db.de>,
	Antoine Ténart 
	<antoine.tenart@...e-electrons.com>
CC:	"sebastian.hesselbarth@...il.com" <sebastian.hesselbarth@...il.com>,
	"balbi@...com" <balbi@...com>,
	"p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
	"alexandre.belloni@...e-electrons.com" 
	<alexandre.belloni@...e-electrons.com>,
	"thomas.petazzoni@...e-electrons.com" 
	<thomas.petazzoni@...e-electrons.com>,
	"zmxu@...vell.com" <zmxu@...vell.com>,
	"jszhang@...vell.com" <jszhang@...vell.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 07/12] usb: chipidea: add a usb2 driver for ci13xxx

 
> >
> > Some people wanted the possibility to set the DMA mask as this USB2 CI
> > driver does not do specific Berlin operation and can be reused later.
> > I don't particularly need to call dma_coerce_mask_and_coherent() in my
> > case, as far as I know.
> 
> Ok, just remove the call then and rely on the default mask.
> 
> > They can maybe give the restrictions they might want to put on the DMA
> > mask.
> 
> If the restriction is from the bus, it should get handled automatically
> by the device probe as long as the correct dma-ranges property is there
> (though we have a small bug there at the moment). If there is a variation
> of ci13xxx that can't do 32-bit DMA, that should use a different
> compatible string and pass a fixed mask into dma_set_mask_and_coherent()
> based on the device.
> 

Correct me if my below understanding is wrong please.

For three chipidea users:
user_a: don't need dma mask
user_b: dma mask value is dma_mask_b
user_c: dma mask value is dma_mask_c

We don't need to call dma_coerce_mask_and_coherent() at generic chipidea
glue driver, and set dma-ranges as dma_mask_b at user_b's dts, and set
dma-ranges as dma_mask_c at user_c's dts.

Peter 
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