Re: [PATCH] misc: pci_endpoint_test: Use memcpy_toio()/memcpy_fromio() for BAR tests

Niklas Cassel
2024-03-19T16:53:55Z

On Tue, Mar 19, 2024 at 10:18:26PM +0530, Manivannan Sadhasivam wrote:
> >
> > I did also see this comment:
> > https://github.com/torvalds/linux/blob/master/Documentation/memory-barriers.txt#L2785-L2790
> >
> > Do you think that we need to perform any flushing after the memset(),
> > to ensure that the data written using memcpy_toio() is actually what
> > we expect it to me?
> >
>
> The documentation recommends cache flushing only if the normal memory write and
> MMIO access are dependent. But here you are just accessing the MMIO. So no
> explicit ordering or cache flushing is required.

What does dependent mean in this case then?

Since the data that we are writing to the device is the data that was
just written to memory using memset().

Kind regards,
Niklas