LinuxLists.cc - Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook

2019-06-06 09:32:36

Subject: Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook

Hi,

On Thu, Jun 06, 2019 at 10:54:51AM +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2019-06-06 at 01:50 +0300, Aaro Koskinen wrote:
> > Hi,
> >
> > When upgrading from v5.0 -> v5.1 on G4 PowerBook, I noticed WLAN does
> > not work anymore:
> >
> > [ 42.004303] b43legacy-phy0: Loading firmware version 0x127, patch level 14 (2005-04-18 02:36:27)
> > [ 42.184837] b43legacy-phy0 debug: Chip initialized
> > [ 42.184873] b43legacy-phy0 ERROR: The machine/kernel does not support the required 30-bit DMA mask
> >
> > The same happens with the current mainline.
>
> How much RAM do you have ?

The system has 1129 MB RAM. Booting with mem=1G makes it work.

A.

2019-06-06 10:57:52

by Benjamin Herrenschmidt

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Subject: Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook

On Thu, 2019-06-06 at 12:31 +0300, Aaro Koskinen wrote:
> Hi,
>
> On Thu, Jun 06, 2019 at 10:54:51AM +1000, Benjamin Herrenschmidt
> wrote:
> > On Thu, 2019-06-06 at 01:50 +0300, Aaro Koskinen wrote:
> > > Hi,
> > >
> > > When upgrading from v5.0 -> v5.1 on G4 PowerBook, I noticed WLAN
> > > does
> > > not work anymore:
> > >
> > > [ 42.004303] b43legacy-phy0: Loading firmware version 0x127,
> > > patch level 14 (2005-04-18 02:36:27)
> > > [ 42.184837] b43legacy-phy0 debug: Chip initialized
> > > [ 42.184873] b43legacy-phy0 ERROR: The machine/kernel does not
> > > support the required 30-bit DMA mask
> > >
> > > The same happens with the current mainline.
> >
> > How much RAM do you have ?
>
> The system has 1129 MB RAM. Booting with mem=1G makes it work.

Wow... that's an odd amount. One thing we could possibly do is add code
to limit the amount of RAM when we detect that device....

Cheers,
Ben.

2019-06-06 10:59:17

by Benjamin Herrenschmidt

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Subject: Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook

On Thu, 2019-06-06 at 20:56 +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2019-06-06 at 12:31 +0300, Aaro Koskinen wrote:
> > Hi,
> >
> > On Thu, Jun 06, 2019 at 10:54:51AM +1000, Benjamin Herrenschmidt
> > wrote:
> > > On Thu, 2019-06-06 at 01:50 +0300, Aaro Koskinen wrote:
> > > > Hi,
> > > >
> > > > When upgrading from v5.0 -> v5.1 on G4 PowerBook, I noticed WLAN
> > > > does
> > > > not work anymore:
> > > >
> > > > [ 42.004303] b43legacy-phy0: Loading firmware version 0x127,
> > > > patch level 14 (2005-04-18 02:36:27)
> > > > [ 42.184837] b43legacy-phy0 debug: Chip initialized
> > > > [ 42.184873] b43legacy-phy0 ERROR: The machine/kernel does not
> > > > support the required 30-bit DMA mask
> > > >
> > > > The same happens with the current mainline.
> > >
> > > How much RAM do you have ?
> >
> > The system has 1129 MB RAM. Booting with mem=1G makes it work.
>
> Wow... that's an odd amount. One thing we could possibly do is add code
> to limit the amount of RAM when we detect that device....

Sent too quickly... I mean that *or* force swiotlb at 30-bits on those systems based
on detecting the presence of that device in the device-tree.

Cheers,
Ben.

2019-06-06 12:39:08

by Christoph Hellwig

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Subject: Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook

On Thu, Jun 06, 2019 at 08:57:49PM +1000, Benjamin Herrenschmidt wrote:
> > Wow... that's an odd amount. One thing we could possibly do is add code
> > to limit the amount of RAM when we detect that device....
>
> Sent too quickly... I mean that *or* force swiotlb at 30-bits on those systems based
> on detecting the presence of that device in the device-tree.

swiotlb doesn't really help you, as these days swiotlb on matters for
the dma_map* case. What would help is a ZONE_DMA that covers these
devices. No need to do the 24-bit x86 does, but 30-bit would do it.

WIP patch for testing below:

diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index b8286a2013b4..7a367ce87c41 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -319,6 +319,10 @@ struct vm_area_struct;
#endif /* __ASSEMBLY__ */
#include <asm/slice.h>

+#if 1 /* XXX: pmac? dynamic discovery? */
+#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

2019-06-06 20:18:30

by Larry Finger

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Subject: Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook

On 6/6/19 6:43 AM, Christoph Hellwig wrote:
> On Thu, Jun 06, 2019 at 08:57:49PM +1000, Benjamin Herrenschmidt wrote:
>>> Wow... that's an odd amount. One thing we could possibly do is add code
>>> to limit the amount of RAM when we detect that device....
>>
>> Sent too quickly... I mean that *or* force swiotlb at 30-bits on those systems based
>> on detecting the presence of that device in the device-tree.
>
> swiotlb doesn't really help you, as these days swiotlb on matters for
> the dma_map* case. What would help is a ZONE_DMA that covers these
> devices. No need to do the 24-bit x86 does, but 30-bit would do it.
>
> WIP patch for testing below:
>
> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
> index b8286a2013b4..7a367ce87c41 100644
> --- a/arch/powerpc/include/asm/page.h
> +++ b/arch/powerpc/include/asm/page.h
> @@ -319,6 +319,10 @@ struct vm_area_struct;
> #endif /* __ASSEMBLY__ */
> #include <asm/slice.h>
>
> +#if 1 /* XXX: pmac? dynamic discovery? */
> +#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
>

I am generating a test kernel with this patch.

FYI, the "free" command on my machine shows 1.5+ G of memory. That likely means
I have 2G installed.

I have tested a patched kernel in which b43legacy falls back to a 31-bit DMA
mask when the 32-bit one failed. That worked, but would likely kill the x86
version. Let me know if think a fix in the driver rather than the kernel would
be better. I still need to understand why the same setup works in b43 and fails
in b43legacy. :(

Larry

2019-06-06 20:19:05

by Larry Finger

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