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

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.

Why? The thing like this I noticed on some other HW which required different
DMA settings. Have you tried to investigate the issue more?

> Move the forced PIO mode DMI quirk to spi-pxa2xx-pci.c (the LPSS host
> controller PCI glue driver) to avoid layering violations in client
> drivers (such as applespi).
> 
> Add an explicit DMI match table for MacBook8,1 and a module parameter
> spi_pxa2xx_force_pio to allow forcing PIO mode on demand.

This looks like a hack. Please, if you have a hardware, try to dump the errors,
collect the data corruption or timeouts and provide more information. DMA for
SPI on LPSS hardware never was a problem (unlike UART in some cases). I'm almost
100% sure the problem is in DMA configuration / setting bits.

...

>  #include <linux/dmaengine.h>
>  #include <linux/platform_data/dma-dw.h>
>   +#include <linux/dmi.h>

Keep list ordered.

>  #include "spi-pxa2xx.h"

...

> +static bool spi_pxa2xx_force_pio;
> +module_param_named(force_pio, spi_pxa2xx_force_pio, bool, 0444);
> +MODULE_PARM_DESC(force_pio, "Force PIO mode (disables DMA) for SPI transfers. ([0] = disabled, 1 = enabled)");

No. There is no room for module parameters like this.

-- 
With Best Regards,
Andy Shevchenko