Re: [PATCH v16 5/7] spi: pxa2xx: disable DMA for Apple MacBook8,1

[Shih-Yuan Lee (FourDollars)]

On Tue, Jul 21, 2026 at 5:18 PM Lukas Wunner <lukas@xxxxxxxxx> wrote:
>
> On Tue, Jul 21, 2026 at 12:21:14AM +0800, Shih-Yuan Lee wrote:
> > On MacBook8,1 (early 2015 12" MacBook), the LPSS SPI controller at
> > 00:15.4 suffers from hardware DMA handshake failures and interrupt
> > routing bugs, causing keyboard/touchpad transactions to fail when
> > DMA is enabled.
> [...]
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=108331
>
> In the bugzilla comments, Leif Liddy writes:
>
>    "I needed to modify drivers/dma/dw/pci.c to assign the DMA controller
>     irq value to 21 (which is what is listed in the ACPI table) for it
>     to work. The DMA controller was being assigned an irq value of 20
>     for some reason."
>
> It would seem better to fix up the incorrect interrupt number in a quirk,
> rather than disabling DMA wholesale.

This is a very good catch!

I appreciate the comment. Based on the Bugzilla feedback regarding the
incorrect interrupt assignment, it seems fixing the IRQ value via a
quirk is indeed a better approach than disabling DMA wholesale. While
I am not certain this will resolve the issue entirely, it looks very
promising. I will investigate the IRQ mis-assignment problem further.

Shih-Yuan