From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gavin Shan Subject: Re: [PATCH v7 38/50] powerpc/powernv: Exclude root bus in pnv_pci_reset_secondary_bus() Date: Fri, 13 Nov 2015 10:25:50 +1100 Message-ID: <20151112232550.GA14719@gwshan> References: <1446642770-4681-1-git-send-email-gwshan@linux.vnet.ibm.com> <1446642770-4681-39-git-send-email-gwshan@linux.vnet.ibm.com> <87lha2zuwg.fsf@gamma.ozlabs.ibm.com> Reply-To: Gavin Shan Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <87lha2zuwg.fsf@gamma.ozlabs.ibm.com> Sender: linux-pci-owner@vger.kernel.org To: Daniel Axtens Cc: Gavin Shan , linuxppc-dev@lists.ozlabs.org, linux-pci@vger.kernel.org, devicetree@vger.kernel.org, benh@kernel.crashing.org, mpe@ellerman.id.au, aik@ozlabs.ru, bhelgaas@google.com, grant.likely@linaro.org, robherring2@gmail.com, panto@antoniou-consulting.com, frowand.list@gmail.com List-Id: devicetree@vger.kernel.org On Fri, Nov 13, 2015 at 09:59:27AM +1100, Daniel Axtens wrote: >Gavin Shan writes: > >> When pnv_pci_reset_secondary_bus() is called to issue reset on >> the indicated secondary bus, the bus can't be root bus. So we >> needn't consider root bus in the function. > >It took me a while to convince myself that this is correct. For the >record, this is why it's correct: > >pnv_pci_reset_secondary_bus fills the reset_secondary_bus callback in >the pci_controller_ops structure, and isn't used elsewhere. > >In arch/powerpc/kernel/pci.c, that callback is called (if it exists) in >pcibios_reset_secondary_bus(). It's not called anywhere else. > >The PPC pcibios_reset_secondary_bus overrides the weak version in >drivers/pci/pci.c. It's called from the same file by >pci_reset_bridge_secondary_device() (and nowhere else). > >pci_reset_bridge_secondary_device() is nicely documented: > >/** > * pci_reset_bridge_secondary_bus - Reset the secondary bus on a PCI bridge. > * @dev: Bridge device > * > * Use the bridge control register to assert reset on the secondary bus. > * Devices on the secondary bus are left in power-on state. > */ > >Therefore, by the definiton of pci_reset_bridge_secondary_bus, >pnv_pci_reset_secondary_bus() can only be called with a bridge >device. As such, a bridge reset only is appropriate. If this breaks >anything, the caller is broken. > >It might be worth including a condensed version of this in the commit >message. > Right. I'll add more description to the changelog in next revision. >Reviewed-by: Daniel Axtens > Thanks, Gavin >Regards, >Daniel Axtens > >> >> Signed-off-by: Gavin Shan >> --- >> arch/powerpc/platforms/powernv/eeh-powernv.c | 12 ++---------- >> 1 file changed, 2 insertions(+), 10 deletions(-) >> >> diff --git a/arch/powerpc/platforms/powernv/eeh-powernv.c b/arch/powerpc/platforms/powernv/eeh-powernv.c >> index a7d84a4..c69b6a1 100644 >> --- a/arch/powerpc/platforms/powernv/eeh-powernv.c >> +++ b/arch/powerpc/platforms/powernv/eeh-powernv.c >> @@ -880,16 +880,8 @@ static int pnv_eeh_bridge_reset(struct pci_dev *dev, int option) >> >> void pnv_pci_reset_secondary_bus(struct pci_dev *dev) >> { >> - struct pci_controller *hose; >> - >> - if (pci_is_root_bus(dev->bus)) { >> - hose = pci_bus_to_host(dev->bus); >> - pnv_eeh_root_reset(hose, EEH_RESET_HOT); >> - pnv_eeh_root_reset(hose, EEH_RESET_DEACTIVATE); >> - } else { >> - pnv_eeh_bridge_reset(dev, EEH_RESET_HOT); >> - pnv_eeh_bridge_reset(dev, EEH_RESET_DEACTIVATE); >> - } >> + pnv_eeh_bridge_reset(dev, EEH_RESET_HOT); >> + pnv_eeh_bridge_reset(dev, EEH_RESET_DEACTIVATE); >> } >> >> /** >> -- >> 2.1.0 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-pci" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html