[PATCH] bus: mhi: host: Allocate entire MHI control config once

[Manivannan Sadhasivam]

On Fri, Apr 25, 2025 at 09:56:05AM -0700, Jeff Johnson wrote:
> On 4/24/2025 10:37 PM, Manivannan Sadhasivam wrote:
> > I was confused by the fact that ath11k driver adds an offset of 0x1000000 to the
> > reserved region for the iova_start:
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/wireless/ath/ath11k/mhi.c?h=v6.15-rc3#n331
> 
> This predates my role as maintainer.
> I was an internal reviewer, but in internal review (as well as the public v1)
> the code was using dedicated 'qcom' DT entries and did not have an offset.
> 
> So I looked at the entire patch history:
> https://lore.kernel.org/linux-wireless/?q=s%3A%22ath11k%3A+Use+reserved+host+DDR+addresses+from+DT+for+PCI+devices%22
> 
> The offset was added in v2.
> 
> There is nothing that describes why the offset was added, and nobody
> questioned it.
> 

Hmm. I'm not sure how this works in the firmware. If firmware uses iova_start as
the start address for the ATU mapping of the MHI data structures, then it won't
be able to access the structures allocated prior to this offset (which would be
very likely).

So the fact that the firmware still works with this offset means it doesn't use
iova at all. But it would be good to remove this offset from the code anyway.

- Mani

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