Re: [PATCH] wifi: ath11k: fix remapped ce accessing issue on 64bit OS

[Sergey Ryazanov]

Hi Jeff,

On 01.05.2024 19:56, Jeff Johnson wrote:
> On 5/1/2024 9:14 AM, Ziyang Huang wrote:
> > On 64bit OS, when ab->mem_ce is lower than or 4G far away from ab->mem,
> > u32 is not enough to store the offsets, which makes ath11k_ahb_read32()
> > and ath11k_ahb_write32() access incorrect address and causes Data Abort
> > Exception.
>
> Are you actually observing this issue?
> Or is this a hypothetical situation?

Yep. This is the real issue. I faced it on IPQ5018 with 64bits kernel.

> > Let's use the high bits of offsets to decide where to access, which is
> > similar as ath11k_pci_get_window_start() done. In the future, we can merge
> > these functions for unified regs accessing.
>
> Performing unnecessary tests and masking for every ioread/write operation will
> potentially impact performance.
>
> What other fixes were considered (i.e. did you consider making all the
> register addresses u64?)

Probably, making argument u64 could also be too much. I/O address space 
of this chip fits 4GB so u32 should be enough. I have a bit different 
fix for this bug. It introduces an indirect call for the CE registers 
access and a dedicated set of accessing functions for chips that has the 
CE region outside the main I/O area. I am going to publish it in a 
couple of weeks, when I will come from a trip. The patch still needs 
some polishing.

--
Sergey