[linux-dvb] saa7134 ioremap() problem

[linux-dvb] saa7134 ioremap() problem

[Andy Burns]

I have been using the saa7134.ko and saa7134_dvb.ko drivers for years as 
part of my mythtv system, working very nicely.

Now I am trying to use xen to virtualise my mythtv-backend, with PCI 
passthrough of the tuner to the virtual machine, everything hasn't gone 
smoothly, but I believe I have found an issue within the driver which 
would have gone un-noticed on a bare-metal machine, yet which causes a 
problem under xen.

Here is what lspci -vvv shows for my card

08:01.0 Multimedia controller: Philips Semiconductors SAA7130 Video 
Broadcast Decoder (rev 01)
         Subsystem: Compro Technology, Inc. Videomate DVB-T200
         Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- 
ParErr- Stepping- SERR- FastB2B- DisINTx-
         Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium 
 >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
         Latency: 64 (21000ns min, 8000ns max)
         Interrupt: pin A routed to IRQ 17
         Region 0: Memory at febffc00 (32-bit, non-prefetchable) [size=1K]
         Capabilities: [40] Power Management version 1
                 Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA 
PME(D0-,D1-,D2-,D3hot-,D3cold-)
                 Status: D0 PME-Enable- DSel=0 DScale=1 PME-
         Kernel modules: saa7134

Notice the MMIO area is 1K in size, but within the driver, it requests 
mapping of a 4K area, rather than 1K.

http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.25.y.git;a=blob;f=drivers/media/video/saa7134/saa7134-core.c;h=58ab163fdbd74e628e60655ea05c5d3bea611599;hb=HEAD#l998

Obviously the kernel will have to round the start/end addresses to the 
nearest 4K boundaries as this is the granularity of page mapping, but if 
the request is too large to begin with it attempts to map two pages, 
straddling the card's physical address range, this works on a physical 
machine, but fails under xen due to more rigourous checking/enforcement 
of permissions.

I have rebuilt the driver module using 0x400 instead of 0x1000 for the 
ioremap() size and the driver then loads, instead of failing (I still 
have an interrupt problem but will follow that up separately).

If you'd like to follow the discussion I've been having on the xen-devel 
list, Keir Fraser should be able to answer questions on why this fails 
under xen far better than I can.

http://lists.xensource.com/archives/html/xen-devel/2008-07/msg00004.html

Could you comment on whether you'd accept a patch for this?


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[linux-dvb] [PATCH] Shrink saa7134 mmio mapped size

[Andy Burns]

The saa7134 driver attempts to map 4K starting from the base address of 
its mmio area, although lspci shows the size of the area is only 1K. The 
excessive mapping goes un-noticed on bare-metal, but is detected and 
denied when the card is used with pci passthrough to a xen domU. If 
shared IRQ is used the "pollirq" kernel option may be required in dom0.

Signed-off-by: Andy Burns <andy@burns.net>
--- drivers/media/video/saa7134/saa7134-core.c.orig     2008-07-01 
16:46:49.000000000 +0100
+++ drivers/media/video/saa7134/saa7134-core.c  2008-07-01 
16:47:10.000000000 +0100
@@ -908,7 +908,7 @@
                        dev->name,(unsigned long 
long)pci_resource_start(pci_dev,0));
                 goto fail1;
         }
-       dev->lmmio = ioremap(pci_resource_start(pci_dev,0), 0x1000);
+       dev->lmmio = ioremap(pci_resource_start(pci_dev,0), 0x400);
         dev->bmmio = (__u8 __iomem *)dev->lmmio;
         if (NULL == dev->lmmio) {
                 err = -EIO;



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Re: [linux-dvb] [PATCH] Shrink saa7134 mmio mapped size

[Matthias Schwarzott]

On Mittwoch, 2. Juli 2008, Andy Burns wrote:
> The saa7134 driver attempts to map 4K starting from the base address of
> its mmio area, although lspci shows the size of the area is only 1K. The
> excessive mapping goes un-noticed on bare-metal, but is detected and
> denied when the card is used with pci passthrough to a xen domU. If
> shared IRQ is used the "pollirq" kernel option may be required in dom0.
>

I have no real insight into the saa7134 core, but at least my card does have a 
memory region of 2K.

lspci -vvnn:
00:0b.0 Multimedia controller [0480]: Philips Semiconductors SAA7133/SAA7135 
Video Broadcast Decoder [1131:7133] (rev d1)
        Subsystem: Avermedia Technologies Inc Device [1461:a7a1]
        Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- 
<TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 32 (63750ns min, 63750ns max)
        Interrupt: pin A routed to IRQ 19
        Region 0: Memory at dfffb800 (32-bit, non-prefetchable) [size=2K]
        Capabilities: [40] Power Management version 2
                Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA 
PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 PME-Enable- DSel=0 DScale=3 PME-
        Kernel driver in use: saa7134
        Kernel modules: saa7134

Regards
Matthias

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Re: [linux-dvb] [PATCH] Shrink saa7134 mmio mapped size

[Andy Burns]

On 02/07/2008 16:12, Matthias Schwarzott wrote:

> I have no real insight into the saa7134 core, but at least my card does have a 
> memory region of 2K.

Thanks, I only have one type of card, I'll try to investigate the best 
way to programatically determine the size of the memory region and use 
that instead of a hard-coded value, then resubmit a new patch.



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Re: [linux-dvb] [PATCH] Shrink saa7134 mmio mapped size

[Andy Burns]

The saa7134 driver attempts to map a fixed 4K starting from the base 
address of its mmio area, regardless of the actual size of the area.
Any excessive mapping may extend past the end of a page, which goes 
un-noticed on bare-metal, but is detected and denied when the card is 
used with pci passthrough to a xen domU. If shared IRQ is used the 
"pollirq" kernel option may be required in dom0.

Signed-off-by: Andy Burns <andy@burns.net>
---- drivers/media/video/saa7134/saa7134-core.c.orig     2008-07-01 
16:46:49.000000000 +0100
+++ drivers/media/video/saa7134/saa7134-core.c  2008-07-02 
16:41:37.000000000 +0100
@@ -908,7 +908,8 @@
                        dev->name,(unsigned long 
long)pci_resource_start(pci_dev,0));
                 goto fail1;
         }
-       dev->lmmio = ioremap(pci_resource_start(pci_dev,0), 0x1000);
+       dev->lmmio = ioremap(pci_resource_start(pci_dev,0),
+                             pci_resource_len(pci_dev,0));
         dev->bmmio = (__u8 __iomem *)dev->lmmio;
         if (NULL == dev->lmmio) {
                 err = -EIO;


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Re: [linux-dvb] [PATCH] Shrink saa7134 mmio mapped size

[hermann pitton]

Hello,

Am Mittwoch, den 02.07.2008, 16:50 +0100 schrieb Andy Burns:
> The saa7134 driver attempts to map a fixed 4K starting from the base 
> address of its mmio area, regardless of the actual size of the area.
> Any excessive mapping may extend past the end of a page, which goes 
> un-noticed on bare-metal, but is detected and denied when the card is 
> used with pci passthrough to a xen domU. If shared IRQ is used the 
> "pollirq" kernel option may be required in dom0.

just a note.

We have some recent remotes sampling from IRQs triggered by a gpio pin
without any additional IR chip.

There are some reports that "pollirq" makes them unusable, since
sensible timings are lost.

No such reports from xen stuff yet, but the same might happen with
shared IRQs and "pollirq" there too.

Cheers,
Hermann


> Signed-off-by: Andy Burns <andy@burns.net>
> ---- drivers/media/video/saa7134/saa7134-core.c.orig     2008-07-01 
> 16:46:49.000000000 +0100
> +++ drivers/media/video/saa7134/saa7134-core.c  2008-07-02 
> 16:41:37.000000000 +0100
> @@ -908,7 +908,8 @@
>                         dev->name,(unsigned long 
> long)pci_resource_start(pci_dev,0));
>                  goto fail1;
>          }
> -       dev->lmmio = ioremap(pci_resource_start(pci_dev,0), 0x1000);
> +       dev->lmmio = ioremap(pci_resource_start(pci_dev,0),
> +                             pci_resource_len(pci_dev,0));
>          dev->bmmio = (__u8 __iomem *)dev->lmmio;
>          if (NULL == dev->lmmio) {
>                  err = -EIO;
> 
> 


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Re: [linux-dvb] [PATCH] Shrink saa7134 mmio mapped size

[Andy Burns]

On 02/07/2008 21:39, hermann pitton wrote:

> We have some recent remotes sampling from IRQs triggered by a gpio pin
> without any additional IR chip.
> 
> There are some reports that "pollirq" makes them unusable, since
> sensible timings are lost.

Thanks for the info, not relevant for me though, the whole point of 
virtualising my mythtv backend with xen is to stuff all the noisy bits 
is a cupboard and have a separate frontend which does have a LiRC device.

> No such reports from xen stuff yet, but the same might happen with
> shared IRQs and "pollirq" there too.

After I'd sorted the mmio mapping issue, the driver loaded under xen, 
but crashed after 40 seconds or so due to shared interrupt routing, so I 
added the pollirq, I understand this might cause performance issues as 
IRQs have to be delivered to multiple drivers in different xen domains, 
particularly one of my PCI slots shares with a PCI-X slot which has my 
8xSATA card in it, so I've avoided that slot for now, but would like to 
have dual tuner again.

The driver is now working fairly well under xen, with a single tuner 
mythbckend can record three concurrent streams from a mux, with under 
10% CPU.

I have one remaining issue, which I will try to track down, every now 
and then I seem to get a DMA error causing a kernel panic, my feeling is 
it happens when retuning;  perhaps some DMA transfer is in-flight when 
something changes on the card and causes a problem? Or like the 
ioremap() it might be something xen is more sensitive to than a 
bare-metal machine.

Do I need to send my patch direct to Harmut Hackmann, or will he pick it 
up from the list if he likes it?



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Re: [linux-dvb] [PATCH] Shrink saa7134 mmio mapped size

[hermann pitton]

Hi,

Am Mittwoch, den 02.07.2008, 22:00 +0100 schrieb Andy Burns:
> On 02/07/2008 21:39, hermann pitton wrote:
> 
> > We have some recent remotes sampling from IRQs triggered by a gpio pin
> > without any additional IR chip.
> > 
> > There are some reports that "pollirq" makes them unusable, since
> > sensible timings are lost.
> 
> Thanks for the info, not relevant for me though, the whole point of 
> virtualising my mythtv backend with xen is to stuff all the noisy bits 
> is a cupboard and have a separate frontend which does have a LiRC device.
> 
> > No such reports from xen stuff yet, but the same might happen with
> > shared IRQs and "pollirq" there too.
> 
> After I'd sorted the mmio mapping issue, the driver loaded under xen, 
> but crashed after 40 seconds or so due to shared interrupt routing, so I 
> added the pollirq, I understand this might cause performance issues as 
> IRQs have to be delivered to multiple drivers in different xen domains, 
> particularly one of my PCI slots shares with a PCI-X slot which has my 
> 8xSATA card in it, so I've avoided that slot for now, but would like to 
> have dual tuner again.
> 
> The driver is now working fairly well under xen, with a single tuner 
> mythbckend can record three concurrent streams from a mux, with under 
> 10% CPU.
> 
> I have one remaining issue, which I will try to track down, every now 
> and then I seem to get a DMA error causing a kernel panic, my feeling is 
> it happens when retuning;  perhaps some DMA transfer is in-flight when 
> something changes on the card and causes a problem? Or like the 
> ioremap() it might be something xen is more sensitive to than a 
> bare-metal machine.
> 
> Do I need to send my patch direct to Harmut Hackmann, or will he pick it 
> up from the list if he likes it?
> 

that depends on the time he has, but if you think you have something
proper, always send a copy directly to Hartmut and Mauro too.

I'm not within any xen, but Gerd, the saa7134 author, is on it since
then. If you think it is xen specific, you might try to reach him too.
(kraxel@redhat.com)

Can't tell, if he has time for it currently.

Cheers,
Hermann






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[linux-dvb] saa7134 ioremap() problem

[Nick Fisk]

Hi,

I also have a card based on the saa7134 chip and I am encountering the
same problem as described in this thread.

My card:-

00:01.0 Multimedia controller: Philips Semiconductors SAA7133/SAA7135
Video Broadcast Decoder (rev d1)
	Subsystem: Avermedia Technologies Inc Unknown device 2c00
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B-
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort-
<TAbort- <MAbort- >SERR- <PERR-
	Latency: 64
	Interrupt: pin A routed to IRQ 16
	Region 0: Memory at febef800 (32-bit, non-prefetchable) [size=2K]
	Capabilities: [40] Power Management version 2
		Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA
PME(D0-,D1-,D2-,D3hot-,D3cold-)
		Status: D0 PME-Enable- DSel=0 DScale=0 PME-




I was wondering if this fix would be included in 2.6.27?

If there is any testing or other information that I can provide that
would help please let me know.

Nick


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