Re: [PATCH] powerpc: enable a 30-bit ZONE_DMA for 32-bit pmac

[Mathieu Malaterre <malat@debian.org>]

On Thu, Jun 13, 2019 at 10:27 AM Christoph Hellwig <hch@lst.de> wrote:
>
> With the strict dma mask checking introduced with the switch to
> the generic DMA direct code common wifi chips on 32-bit powerbooks
> stopped working.  Add a 30-bit ZONE_DMA to the 32-bit pmac builds
> to allow them to reliably allocate dma coherent memory.
>
> Fixes: 65a21b71f948 ("powerpc/dma: remove dma_nommu_dma_supported")
> Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  arch/powerpc/include/asm/page.h         | 7 +++++++
>  arch/powerpc/mm/mem.c                   | 3 ++-
>  arch/powerpc/platforms/powermac/Kconfig | 1 +
>  3 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
> index b8286a2013b4..0d52f57fca04 100644
> --- a/arch/powerpc/include/asm/page.h
> +++ b/arch/powerpc/include/asm/page.h
> @@ -319,6 +319,13 @@ struct vm_area_struct;
>  #endif /* __ASSEMBLY__ */
>  #include <asm/slice.h>
>
> +/*
> + * Allow 30-bit DMA for very limited Broadcom wifi chips on many powerbooks.

nit: would it be possible to mention explicit reference to b43-legacy.
Using b43 on my macmini g4 never showed those symptoms (using
5.2.0-rc2+)

$ dmesg | grep b43
[   14.327189] bus: 'pci': add driver b43-pci-bridge
[   14.345354] bus: 'pci': driver_probe_device: matched device
0001:10:12.0 with driver b43-pci-bridge
[   14.380110] bus: 'pci': really_probe: probing driver b43-pci-bridge
with device 0001:10:12.0
[   14.440295] b43-pci-bridge 0001:10:12.0: enabling device (0004 -> 0006)
[   14.637223] b43-pci-bridge 0001:10:12.0: Sonics Silicon Backplane
found on PCI device 0001:10:12.0
[   14.644858] driver: 'b43-pci-bridge': driver_bound: bound to device
'0001:10:12.0'
[   14.743341] bus: 'pci': really_probe: bound device 0001:10:12.0 to
driver b43-pci-bridge
[   18.724343] bus: 'bcma': add driver b43
[   18.728635] bus: 'ssb': add driver b43
[   18.734305] bus: 'ssb': driver_probe_device: matched device ssb0:0
with driver b43
[   18.743155] bus: 'ssb': really_probe: probing driver b43 with device ssb0:0
[   18.747782] b43-phy0: Broadcom 4306 WLAN found (core revision 5)
[   18.767439] b43-phy0: Found PHY: Analog 2, Type 2 (G), Revision 2
[   18.771759] b43-phy0: Found Radio: Manuf 0x17F, ID 0x2050, Revision
2, Version 0
[   18.795467] driver: 'b43': driver_bound: bound to device 'ssb0:0'
[   18.801533] bus: 'ssb': really_probe: bound device ssb0:0 to driver b43
[   22.143084] b43-phy0: Loading firmware version 666.2 (2011-02-23 01:15:07)
[   25.133011] b43 ssb0:0 wlan0: disabling HT as WMM/QoS is not
supported by the AP
[   25.140221] b43 ssb0:0 wlan0: disabling VHT as WMM/QoS is not
supported by the AP


> + */
> +#ifdef CONFIG_PPC32
> +#define ARCH_ZONE_DMA_BITS 30
> +#else
>  #define ARCH_ZONE_DMA_BITS 31
> +#endif
>
>  #endif /* _ASM_POWERPC_PAGE_H */
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index cba29131bccc..2540d3b2588c 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -248,7 +248,8 @@ void __init paging_init(void)
>                (long int)((top_of_ram - total_ram) >> 20));
>
>  #ifdef CONFIG_ZONE_DMA
> -       max_zone_pfns[ZONE_DMA] = min(max_low_pfn, 0x7fffffffUL >> PAGE_SHIFT);
> +       max_zone_pfns[ZONE_DMA] = min(max_low_pfn,
> +                       ((1UL << ARCH_ZONE_DMA_BITS) - 1) >> PAGE_SHIFT);
>  #endif
>         max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
>  #ifdef CONFIG_HIGHMEM
> diff --git a/arch/powerpc/platforms/powermac/Kconfig b/arch/powerpc/platforms/powermac/Kconfig
> index f834a19ed772..c02d8c503b29 100644
> --- a/arch/powerpc/platforms/powermac/Kconfig
> +++ b/arch/powerpc/platforms/powermac/Kconfig
> @@ -7,6 +7,7 @@ config PPC_PMAC
>         select PPC_INDIRECT_PCI if PPC32
>         select PPC_MPC106 if PPC32
>         select PPC_NATIVE
> +       select ZONE_DMA if PPC32
>         default y
>
>  config PPC_PMAC64
> --
> 2.20.1
>