how to specify dma_mask and coherent_dma_mask in hwmod

Bedia, Vaibhav vaibhav.bedia at
Fri Jun 29 07:23:52 EDT 2012

Hi Paul,

On Thu, Jun 28, 2012 at 22:02:46, Paul Walmsley wrote:
> On Thu, 28 Jun 2012, Bedia, Vaibhav wrote:
> > On Thu, Jun 28, 2012 at 21:22:54, Paul Walmsley wrote:
> > [...]
> > > 
> > > dma_mask and coherent_dma_mask can be specified during 
> > > device creation.  See usb_musb_init() in arch/arm/mach-omap2/usb-musb.c 
> > > for an example.
> > > 
> > 
> > Thanks for pointing this out. Should omap_device_build() start handling this
> > or would that be an overkill?
> If both dma_mask and coherent_dma_mask are always 0xffffffff on all OMAPs 
> and we can set that safely even for devices that don't use it, then yeah 
> it sounds like we should set it.
> Care to send a patch?

I just grepped for the any other user of this under mach-omap2 and plat-omap
and there are a few other places where it's getting used. All of them are
setting it to 0xffffffff and same is the case with the CPSW driver. 

I don't know much about the dma stuff so I am bit reluctant in setting this
unconditionally. I looked at setting the mask based on a flag during
omap_device_build() but an additional flag in the API will cause all the users
to be changed. We could perhaps extend the omap_hwmod structure for passing on
this information. Or for CPSW we could stick with approach that's been adopted
in usb_musb_init(). Which approach sounds better to you?

Vaibhav B.

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