Re: [PATCH] PCI: rcar: Always allocate MSI addresses in 32bit space

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Marek,

On Fri, Oct 16, 2020 at 2:04 PM <marek.vasut@gmail.com> wrote:
> From: Marek Vasut <marek.vasut+renesas@gmail.com>
>
> This fixes MSI operation on legacy PCI cards, which cannot issue 64bit MSIs.
> The R-Car controller only has one MSI trigger address instead of two, one
> for 64bit and one for 32bit MSI, set the address to 32bit PCIe space so that
> legacy PCI cards can also trigger MSIs.
>
> Fixes: 290c1fb35860 ("PCI: rcar: Add MSI support for PCIe")
> Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>

Thanks for your patch!

Seems to work, on both R-Car M2-W and M3-W, as
virt_to_phys((void *)msi->pages) points to RAM below the 4 GiB limit, so
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

> --- a/drivers/pci/controller/pcie-rcar-host.c
> +++ b/drivers/pci/controller/pcie-rcar-host.c
> @@ -753,7 +753,7 @@ static int rcar_pcie_enable_msi(struct rcar_pcie_host *host)
>         }
>
>         /* setup MSI data target */
> -       msi->pages = __get_free_pages(GFP_KERNEL, 0);
> +       msi->pages = __get_free_pages(GFP_KERNEL | GFP_DMA32, 0);

BTW, can this fail, especially now this is allocated from a more
limited pool?

>         rcar_pcie_hw_enable_msi(host);
>
>         return 0;

Regardless:
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds