| From: Casey Leedom [lee...@chelsio.com]
| Sent: Thursday, May 07, 2015 4:31 PM
|
| | From: Bjorn Helgaas [bhelg...@google.com]
| | Sent: Thursday, May 07, 2015 4:04 PM
| |
| | There are a lot of fixups in drivers/pci/quirks.c. For things that have to
| | be worked around either before a driver claims the device or if there is no
| | driver at all, the fixup *has* to go in drivers/pci/quirks.c
| |
| | But for things like this, where the problem can only occur after a driver
| | claims the device, I think it makes more sense to put the fixup in the
| | driver itself. The only wrinkle here is that the fixup has to be done on a
| | separate device, not the device claimed by the driver. But I think it
| | probably still makes sense to put this fixup in the driver.
| ...
| One complication to doing this in cxgb4 is that it attaches to Physical
| Function 4 of our T5 chip. Meanwhile, a completely separate storage
| driver, csiostor, connections to PF5 and PF6 and there's no
| requirement at all that cxgb4 be loaded. So if we go down the road of
| putting the fixup code in the cxgb4 driver, we'll also need to duplicate
| that code in the csiostor driver.
I never heard back on this issue of needing to put the Root Complex "fixup"
code in two different drivers -- cxgb4 and csiostor -- if we don't go down the
path of using a PCI Quirk. I'm happy doing either and have verified both
solutions locally. I'd just like to get a judgement call on this.
It comes down to adding ~30 lines to
drivers/net/eththernet/chelsio/cxgb4/cxgb4_main.c
drivers/scsi/csiostor/csio_init.c
or ~30 lines to
drivers/pci/quirks.c
| | Can you include a pointer to the relevant part of the spec?
|
| Sure:
|
| 2.2.9. Completion Rules
| ...
| Completion headers must supply the same values for
| the Attribute as were supplied in the 20 header of
| the corresponding Request, except as explicitly
| allowed when IDO is used (see Section 2.2.6.4).
| ...
| 2.3.2. Completion Handling Rules
| ...
| If a received Completion matches the Transaction ID
| of an outstanding Request, but in some other way
| does not match the corresponding Request (e.g., a
| problem with Attributes, Traffic Class, Byte Count,
| Lower Address, etc), it is strongly recommended for
| the Receiver to handle the Completion as a Malformed
| TLP. However, if the Completion is otherwise properly
| formed, it is permitted[22] for the Receiver to
| handle the Completion as an Unexpected Completion.
| | Can you use pci_upstream_bridge() here? There are a couple places where we
| | want to find the Root Port, so we might factor that out someday. It'll be
| | easier to find all those places if they use with pci_upstream_bridge().
|
| It looks like pci_upstream_bridge() just traverses one like upstream toward
the
| Root Complex? Or am I misunderstanding that function?
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