Re: [PATCH v2 1/3] PCI: mediatek: Allocate MSI address with dmam_alloc_coherent()

Marc Zyngier
2024-06-09T12:33:06Z

On Sat, 08 Jun 2024 10:01:52 +0100,
Manivannan Sadhasivam <mani@kernel.org> wrote:
>
> On Mon, Dec 11, 2023 at 04:52:54PM +0800, Jianjun Wang wrote:
> > Use dmam_alloc_coherent() to allocate the MSI address, instead of using
> > virt_to_phys().
> >
>
> What is the reason for this change? So now PCIE_MSI_VECTOR becomes unused?

More importantly, this is yet another example of the DW reference
driver nonsense, where memory is allocated for *MSI*, while the whole
point of MSIs is that it is a write that doesn't target memory, making
any form of RAM allocation absolutely pointless.

This silly approach has been cargo-culted for years, and while I
caught a few in my time, you can't beat copy-paste.

IMO, this patch is only making things worse instead of fixing things.

M.

--
Without deviation from the norm, progress is not possible.