From patchwork Fri Apr 19 15:22:24 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Alex G." 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[98.195.139.126]) by smtp.gmail.com with ESMTPSA id y9sm1981723otk.20.2019.04.19.08.23.10 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 19 Apr 2019 08:23:11 -0700 (PDT) From: Alexandru Gagniuc To: bhelgaas@google.com Cc: austin_bolen@dell.com, alex_gagniuc@dellteam.com, keith.busch@intel.com, Shyam_Iyer@Dell.com, lukas@wunner.de, Alexandru Gagniuc , "Rafael J. Wysocki" , Andy Shevchenko , Mika Westerberg , "Gustavo A. R. Silva" , Sinan Kaya , Oza Pawandeep , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 2/4] PCI: pciehp: Do not turn off slot if presence comes up after link Date: Fri, 19 Apr 2019 10:22:24 -0500 Message-Id: <20190419152238.12251-3-mr.nuke.me@gmail.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190419152238.12251-1-mr.nuke.me@gmail.com> References: <20190419000148.GI126710@google.com> <20190419152238.12251-1-mr.nuke.me@gmail.com> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org According to PCIe 3.0, the presence detect state is a logical OR of in-band and out-of-band presence. With this, we'd expect the presence state to always be asserted when the link comes up. Not all hardware follows this, and it is possible for the presence to come up after the link. In this case, the PCIe device would be erroneously disabled and re-probed. It is possible to distinguish between a delayed presence and a card swap by looking at the DLL state changed bit -- The link has to come down if the card is removed. Thus, for a device that is probed, present and has its link active, a lack of a link state change event guarantees we have the same device, and shutdown is not needed. Signed-off-by: Alexandru Gagniuc --- drivers/pci/hotplug/pciehp_ctrl.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c index 905282a8ddaa..d46724f0b4ce 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -217,6 +217,22 @@ void pciehp_handle_disable_request(struct controller *ctrl) ctrl->request_result = pciehp_disable_slot(ctrl, SAFE_REMOVAL); } +static bool is_delayed_presence_up_event(struct controller *ctrl, u32 events) +{ + bool present, link_active; + + if (!ctrl->inband_presence_disabled) + return false; + + present = pciehp_card_present(ctrl); + link_active = pciehp_check_link_active(ctrl); + + if (!present || !link_active || events & PCI_EXP_SLTSTA_DLLSC) + return false; + + return true; +} + void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) { bool present, link_active; @@ -224,6 +240,9 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) /* * If the slot is on and presence or link has changed, turn it off. * Even if it's occupied again, we cannot assume the card is the same. + * + * An exception is a delayed "Card present" after a "Link Up". This can + * happen on controllers with in-band presence disabled. */ mutex_lock(&ctrl->state_lock); switch (ctrl->state) { @@ -231,6 +250,11 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) cancel_delayed_work(&ctrl->button_work); /* fall through */ case ON_STATE: + if (is_delayed_presence_up_event(ctrl, events)) { + mutex_unlock(&ctrl->state_lock); + ctrl_dbg(ctrl, "Presence state came up after link"); + return; + } ctrl->state = POWEROFF_STATE; mutex_unlock(&ctrl->state_lock); if (events & PCI_EXP_SLTSTA_DLLSC)