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Thu, 28 Jan 2021 23:11:54 -0800 Received: from MTKMBS31N2.mediatek.inc (172.27.4.87) by MTKMBS62N1.mediatek.inc (172.29.193.41) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Thu, 28 Jan 2021 23:11:53 -0800 Received: from MTKCAS36.mediatek.inc (172.27.4.186) by MTKMBS31N2.mediatek.inc (172.27.4.87) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 29 Jan 2021 15:11:46 +0800 Received: from mcddlt001.mediatek.inc (10.19.240.15) by MTKCAS36.mediatek.inc (172.27.4.170) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Fri, 29 Jan 2021 15:11:45 +0800 From: To: , Subject: [v3] PCI: Avoid unsync of LTR mechanism configuration Date: Fri, 29 Jan 2021 15:11:37 +0800 Message-ID: <20210129071137.8743-1-mingchuang.qiao@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 X-TM-SNTS-SMTP: D09C1C281E76E7598B4674A7DB4AB076AF2D879ACA6C536492D37C5A40A3E4C32000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210129_021159_233253_819BCEBE X-CRM114-Status: GOOD ( 13.76 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mika.westerberg@linux.intel.com, kerun.zhu@mediatek.com, linux-pci@vger.kernel.org, lambert.wang@mediatek.com, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, alex.williamson@redhat.com, linux-mediatek@lists.infradead.org, utkarsh.h.patel@intel.com, haijun.liu@mediatek.com, mingchuang.qiao@mediatek.com, linux-arm-kernel@lists.infradead.org Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org From: Mingchuang Qiao In bus scan flow, the "LTR Mechanism Enable" bit of DEVCTL2 register is configured in pci_configure_ltr(). If device and bridge both support LTR mechanism, the "LTR Mechanism Enable" bit of device and bridge will be enabled in DEVCTL2 register. And pci_dev->ltr_path will be set as 1. If PCIe link goes down when device resets, the "LTR Mechanism Enable" bit of bridge will change to 0 according to PCIe r5.0, sec 7.5.3.16. However, the pci_dev->ltr_path value of bridge is still 1. For following conditions, check and re-configure "LTR Mechanism Enable" bit of bridge to make "LTR Mechanism Enable" bit mtach ltr_path value. -before configuring device's LTR for hot-remove/hot-add -before restoring device's DEVCTL2 register when restore device state Signed-off-by: Mingchuang Qiao --- changes of v2 -modify patch description -reconfigure bridge's LTR before restoring device DEVCTL2 register changes of v3 -call pci_reconfigure_bridge_ltr() in probe.c --- drivers/pci/pci.c | 25 +++++++++++++++++++++++++ drivers/pci/pci.h | 1 + drivers/pci/probe.c | 13 ++++++++++--- 3 files changed, 36 insertions(+), 3 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b9fecc25d213..12b557c8f062 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1437,6 +1437,24 @@ static int pci_save_pcie_state(struct pci_dev *dev) return 0; } +void pci_reconfigure_bridge_ltr(struct pci_dev *dev) +{ +#ifdef CONFIG_PCIEASPM + struct pci_dev *bridge; + u32 ctl; + + bridge = pci_upstream_bridge(dev); + if (bridge && bridge->ltr_path) { + pcie_capability_read_dword(bridge, PCI_EXP_DEVCTL2, &ctl); + if (!(ctl & PCI_EXP_DEVCTL2_LTR_EN)) { + pci_dbg(bridge, "re-enabling LTR\n"); + pcie_capability_set_word(bridge, PCI_EXP_DEVCTL2, + PCI_EXP_DEVCTL2_LTR_EN); + } + } +#endif +} + static void pci_restore_pcie_state(struct pci_dev *dev) { int i = 0; @@ -1447,6 +1465,13 @@ static void pci_restore_pcie_state(struct pci_dev *dev) if (!save_state) return; + /* + * Downstream ports reset the LTR enable bit when link goes down. + * Check and re-configure the bit here before restoring device. + * PCIe r5.0, sec 7.5.3.16. + */ + pci_reconfigure_bridge_ltr(dev); + cap = (u16 *)&save_state->cap.data[0]; pcie_capability_write_word(dev, PCI_EXP_DEVCTL, cap[i++]); pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]); diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 5c59365092fa..a660a01358c5 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -111,6 +111,7 @@ void pci_free_cap_save_buffers(struct pci_dev *dev); bool pci_bridge_d3_possible(struct pci_dev *dev); void pci_bridge_d3_update(struct pci_dev *dev); void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev); +void pci_reconfigure_bridge_ltr(struct pci_dev *dev); static inline void pci_wakeup_event(struct pci_dev *dev) { diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 953f15abc850..fa6075093f3b 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -2132,9 +2132,16 @@ static void pci_configure_ltr(struct pci_dev *dev) * Complex and all intermediate Switches indicate support for LTR. * PCIe r4.0, sec 6.18. */ - if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT || - ((bridge = pci_upstream_bridge(dev)) && - bridge->ltr_path)) { + if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) { + pcie_capability_set_word(dev, PCI_EXP_DEVCTL2, + PCI_EXP_DEVCTL2_LTR_EN); + dev->ltr_path = 1; + return; + } + + bridge = pci_upstream_bridge(dev); + if (bridge && bridge->ltr_path) { + pci_reconfigure_bridge_ltr(dev); pcie_capability_set_word(dev, PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_LTR_EN); dev->ltr_path = 1;