Re: [PATCH] ARM: dts: dra7: Add bus_dma_limit for L3 bus

[Roger Quadros]

On 10/03/2020 17:48, Tony Lindgren wrote:
> * Tero Kristo <t-kristo@xxxxxx> [200310 14:46]:
> > On 10/03/2020 13:53, Roger Quadros wrote:
> > > The L3 interconnect can access only 32-bits of address.
> > > Add the dma-ranges property to reflect this limit.
> > >
> > > This will ensure that no device under L3 is
> > > given > 32-bit address for DMA.
> > >
> > > Issue was observed only with SATA on DRA7-EVM with 4GB RAM
> > > and CONFIG_ARM_LPAE enabled. This is because the controller
> > > can perform 64-bit DMA and was setting the dma_mask to 64-bit.
> > >
> > > Setting the correct bus_dma_limit fixes the issue.
> >
> > This seems kind of messy to modify almost every DT node because of this....
> > Are you sure this is the only way to get it done? No way to modify the sata
> > node only which is impacted somehow?
> >
> > Also, what if you just pass 0xffffffff to the dma-ranges property? That
> > would avoid modifying every node I guess.
>
> Also, I think these interconnects are not limited to 32-bit access.

But from Table 2-1. L3_MAIN Memory Map

Start address	0x0000_0000
End address	0xFFFF_FFFF

So it is 32-bit limit, right?

> So yeah I too would prefer a top level dma-ranges property assuming
> that works.
>
> I guess there dma-ranges should not be 0xffffffff though if
> limited to 2GB :)
>
> Regards,
>
> Tony

--
cheers,
-roger
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