linux-kernel - Re: MSI messages

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Date:	Mon, 22 Dec 2008 03:05:41 +0400
From:	Manu Abraham <abraham.manu@...il.com>
To:	michael@...erman.id.au
CC:	Grant Grundler <grundler@...isc-linux.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: MSI messages

Michael Ellerman wrote:
> On Sun, 2008-12-21 at 01:13 +0400, Manu Abraham wrote:
>> Grant Grundler wrote:
>>> On Sun, Dec 14, 2008 at 03:15:15PM +0400, Manu Abraham wrote:
>>> ...
>>>>> A "GSI" (Generic Sys Interrupt?) is associated with each entry in
>>>>> the MSI-X table. Driver then calls request_irq() to bind an interrupt
>>>>> handler to each GSI. So the driver never directly sees the "message".
>>>> Oh, you mean the array of irq_handlers in the MSI-X table should 
>>>> correspond to a particular message ?
>>> No. I mean each MSI-X entry has an address+message pair and each MSI-X entry
>>> is associated with the parameters passed to each call of request_irq().
>>> Pass in unique private data to each call of request_irq() and the driver
>>> can determine which message was delivered when the ISR gets called.
>>> (ISR == Interrupt Service Routine, aka driver IRQ handler)
>>
>> Is it possible that even when the config space says that multiple messages 
>> are supported, you cannot enable MSI-X ?
> 
> Yes, absolutely. Have a look at pci_msi_check_device() for starters. MSI
> can be disabled globally, or per-device by a quirk, the bridges above
> your device might not support MSI and the arch code may prevent
> MSI/MSI-X for some reason (ie. platform doesn't support it).

It seems that the bridge does support MSI. It looks like my video device is 
using MSI.


Regards,
Manu

pci 0000:01:00.0: Boot video device                                                                            
PCI: Setting latency timer of device 0000:00:01.0 to 64                                                        
assign_interrupt_mode Found MSI capability                                                                     
Allocate Port Service[0000:00:01.0:pcie00]                                                                     
PCI: Setting latency timer of device 0000:00:1c.0 to 64                                                        
assign_interrupt_mode Found MSI capability                                                                     
Allocate Port Service[0000:00:1c.0:pcie00]                                                                     
Allocate Port Service[0000:00:1c.0:pcie02]                                                                     
PCI: Setting latency timer of device 0000:00:1c.1 to 64                                                        
assign_interrupt_mode Found MSI capability                                                                     
Allocate Port Service[0000:00:1c.1:pcie00]                                                                     
Allocate Port Service[0000:00:1c.1:pcie02]                                                                     
PCI: Setting latency timer of device 0000:00:1c.2 to 64                                                        
assign_interrupt_mode Found MSI capability                                                                     
Allocate Port Service[0000:00:1c.2:pcie00]                                                                     
Allocate Port Service[0000:00:1c.2:pcie02]                                                                     
PCI: Setting latency timer of device 0000:00:1c.3 to 64                                                        
assign_interrupt_mode Found MSI capability                                                                     
Allocate Port Service[0000:00:1c.3:pcie00]                                                                     
Allocate Port Service[0000:00:1c.3:pcie02]                                                                     
PCI: Setting latency timer of device 0000:00:1c.4 to 64                                                        
assign_interrupt_mode Found MSI capability                                                                     
Allocate Port Service[0000:00:1c.4:pcie00]                                                                     
Allocate Port Service[0000:00:1c.4:pcie02]                                                                     
vesafb: framebuffer at 0x91000000, mapped to 0xf8880000, using 10240k, total 14336k                            
vesafb: mode is 1280x1024x16, linelength=2560, pages=1


04:00.0 Multimedia controller: Philips Semiconductors Device 7160 (rev 02)
        Subsystem: Technotrend Systemtechnik GmbH Device 3009
        Flags: bus master, fast devsel, latency 0, IRQ 11
        Memory at 93b00000 (64-bit, non-prefetchable) [size=1M]
        Capabilities: <access denied>

05:00.0 Multimedia controller: Philips Semiconductors Device 7160 (rev 01)
        Subsystem: Philips Semiconductors Device 0000
        Flags: bus master, fast devsel, latency 0, IRQ 19
        Memory at 93a00000 (64-bit, non-prefetchable) [size=1M]
        Capabilities: <access denied>
        Kernel driver in use: SAA716x Hybrid

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