Re: [PATCH] dra7: sata: Fix SATA with CONFIG_ARM_LPAE enabled

[Tony Lindgren <tony@atomide.com>]

* Roger Quadros <rogerq@ti.com> [200305 16:47]:
> +Nishanth
> 
> Robin,
> 
> On 05/03/2020 18:04, Robin Murphy wrote:
> > On 04/03/2020 9:00 am, Roger Quadros wrote:
> > > Even though the TRM says that SATA IP has 36 address bits
> > > wired in the SoC, we see bus errors whenever any address
> > > greater than 32-bit is given to the controller.
> > 
> > Actually, is it really just SATA? I pulled up a couple of DRA7xx TRMs out of curiosity - thanks for having such easy-to-access documentation by the way :) - and they both give me a clear impression that the entire L3_MAIN interconnect is limited to 32-bit addresses and thus pretty much all the DMA masters should only be able to touch the lower 2GB of DRAM. Especially the bit that explicitly says "This is a high address range (Q8 – Q15) that requires an address greater than 32 bits. This space is visible only for the MPU Subsystem."
> 
> You are right that L3 interconnect can only access first 2GB of DRAM.
> Which means we should add the bus_dma_limit to the entire L3 bus
> instead of just SATA?

OK makes sense to me.

> > Is it in fact the case that the SATA driver happens to be the only one to set a >32-bit DMA mask on your system?
> 
> This looks like the case. Other device drivers might not be overriding
> dma_mask at all thus using the default 32-bit dma_mask.

OK

Regards,

Tony