Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH V3 1/2] Drivers/PCI: Export pcie_has_flr() interface | From | Govinda Tatti <> | Date | Fri, 15 Dec 2017 09:48:02 -0600 |
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Thanks Bjorn and Christophfor your response. Please see below for my comments.
On 12/13/2017 3:24 PM, Bjorn Helgaas wrote: > [+cc Christoph] > > On Wed, Dec 13, 2017 at 02:46:57PM -0600, Govinda Tatti wrote: >>>>>> -static bool pcie_has_flr(struct pci_dev *dev) >>>>>> +bool pcie_has_flr(struct pci_dev *dev) >>>>>> { >>>>>> u32 cap; >>>>>> @@ -3882,6 +3882,7 @@ static bool pcie_has_flr(struct pci_dev *dev) >>>>>> pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &cap); >>>>>> return cap & PCI_EXP_DEVCAP_FLR; >>>>>> } >>>>>> +EXPORT_SYMBOL_GPL(pcie_has_flr); >>>>> I'd rather change pcie_flr() so you could *always* call it, and it >>>>> would return 0, -ENOTTY, or whatever, based on whether FLR is >>>>> supported. Is that feasible? >>>> Sure, I will add pcie_has_flr() logic inside pcie_flr() and return >>>> appropriate >>>> values as suggested by you. Do we still want to retain pcie_has_flr() and >>>> its usage inside pci.c?.Otherwise, I will remove it and do required cleanup. >>> If you can restructure the code and remove pcie_has_flr() while >>> retaining the existing behavior of its callers, that would be great. >> I checked the current usage of pcie_has_flr() and pcie_flr(). I have >> a couple >> of questions or need some clarification. >> >> 1. pcie_has_flr() usage inside pci_probe_reset_function(). >> >> This function is only calling pcie_has_flr() but not pcie_flr(). >> Rest of the code is trying to do specific type of reset except >> pcie_flr(). >> >> rc = pci_dev_specific_reset(dev, 1); >> if (rc != -ENOTTY) >> return rc; >> if (pcie_has_flr(dev)) >> return 0; >> rc = pci_af_flr(dev, 1); >> if (rc != -ENOTTY) >> return rc; >> >> In other-words, I can remove usage of pcie_has_flr() in all other places >> in pci.c except in above function. > I think we should keep the EXPORT_SYMBOL_GPL() part of a60a2b73ba69 > ("PCI: Export pcie_flr()"), but revert the restructuring part. > > Prior to a60a2b73ba69, we had > > int pcie_flr(struct pci_dev *dev, int probe); > > like all the other reset methods. AFAICT, the addition of > pcie_has_flr() was to optimize the path slightly because when drivers > call pcie_flr(), they should already know that their hardware supports > FLR. But I don't think that optimization is worth the extra code > complexity. If we do need to optimize it, we can check this in the > core during enumeration and set PCI_DEV_FLAGS_NO_FLR_RESET > accordingly. > > Christoph, chime in if I'm missing something here. Not all code paths are aware of FLR capability and also, not using pcie_flr(). For example,
arch/powerpc/platforms/powernv/eeh-powernv.c drivers/crypto/cavium/nitrox/nitrox_main.c drivers/net/ethernet/cavium/liquidio/octeon_mailbox.c
So, we should consider one of these options.
- set PCI_DEV_FLAGS_NO_FLR_RESET if it is not supported. - pcie_flr() should return if it is not supported
If we modify pcie_flr() to return error codes, then we need to modify all existing modules that are calling this function.
Please let me know your preference, so that I can move accordingly. Thanks.
Cheers GOVINDA
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