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[98.195.139.126]) by smtp.gmail.com with ESMTPSA id d67sm8000424oig.36.2019.02.19.17.20.54 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 19 Feb 2019 17:20:55 -0800 (PST) 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, okaya@kernel.org, linux-pci@vger.kernel.org, Alexandru Gagniuc , "Gustavo A. R. Silva" , linux-kernel@vger.kernel.org Subject: [PATCH RFC v2 2/4] PCI: pciehp: Do not turn off slot if presence comes up after link Date: Tue, 19 Feb 2019 19:20:28 -0600 Message-Id: <20190220012031.10741-3-mr.nuke.me@gmail.com> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20190220012031.10741-1-mr.nuke.me@gmail.com> References: <20190220012031.10741-1-mr.nuke.me@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 3f3df4c29f6e..28965995ebb9 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -213,6 +213,21 @@ 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; @@ -220,13 +235,22 @@ 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. + * When the card is swapped, we also expect a change in link state, + * without which, it's likely presence became high after link-active. */ mutex_lock(&ctrl->state_lock); + present = pciehp_card_present(ctrl); + link_active = pciehp_check_link_active(ctrl); switch (ctrl->state) { case BLINKINGOFF_STATE: 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) -- 2.19.2