Re: [PATCH v2 2/3] PCI: qcom: Read back PARF_LTSSM register

From: Konrad Dybcio
Date: Wed Feb 14 2024 - 16:35:34 EST

On 12.02.2024 22:17, Bjorn Helgaas wrote:
> Maybe include the reason in the subject? "Read back" is literally
> what the diff says.
> On Sat, Feb 10, 2024 at 06:10:06PM +0100, Konrad Dybcio wrote:
>> To ensure write completion, read the PARF_LTSSM register after setting
>> the LTSSM enable bit before polling for "link up".
> The write will obviously complete *some* time; I assume the point is
> that it's important for it to complete before some other event, and it
> would be nice to know why that's important.

Right, that's very much meaningful on non-total-store-ordering
architectures, like arm64, where the CPU receives a store instruction,
but that does not necessarily impact the memory/MMIO state immediately.