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Tue, 24 Jul 2018 12:53:22 -0700 (PDT) Message-ID: <1532461998.20066.5.camel@gmail.com> Subject: Re: [PATCH v3 2/3] PCI: Samsung SM961/PM961 NVMe disable before FLR quirk From: Minwoo Im To: Alex Williamson , linux-pci@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org Date: Wed, 25 Jul 2018 04:53:18 +0900 In-Reply-To: <20180724161440.2729.89835.stgit@gimli.home> References: <20180724160440.2729.75178.stgit@gimli.home> <20180724161440.2729.89835.stgit@gimli.home> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.5.2-0ubuntu3.2 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Alex, On Tue, 2018-07-24 at 10:14 -0600, Alex Williamson wrote: > The Samsung SM961/PM961 (960 EVO) sometimes fails to return from FLR > with the PCI config space reading back as -1.  A reproducible instance > of this behavior is resolved by clearing the enable bit in the NVMe > configuration register and waiting for the ready status to clear > (disabling the NVMe controller) prior to FLR. > > Signed-off-by: Alex Williamson > --- >  drivers/pci/quirks.c |   83 > ++++++++++++++++++++++++++++++++++++++++++++++++++ >  1 file changed, 83 insertions(+) > > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c > index e72c8742aafa..3899cdd2514b 100644 > --- a/drivers/pci/quirks.c > +++ b/drivers/pci/quirks.c > @@ -28,6 +28,7 @@ >  #include >  #include >  #include > +#include >  #include /* isa_dma_bridge_buggy */ >  #include "pci.h" >   > @@ -3669,6 +3670,87 @@ static int reset_chelsio_generic_dev(struct pci_dev > *dev, int probe) >  #define PCI_DEVICE_ID_INTEL_IVB_M_VGA      0x0156 >  #define PCI_DEVICE_ID_INTEL_IVB_M2_VGA     0x0166 >   > +/* > + * The Samsung SM961/PM961 controller can sometimes enter a fatal state after > + * FLR where config space reads from the device return -1.  We seem to be > + * able to avoid this condition if we disable the NVMe controller prior to > + * FLR.  This quirk is generic for any NVMe class device requiring similar > + * assistance to quiesce the device prior to FLR. > + * > + * NVMe specification: https://nvmexpress.org/resources/specifications/ > + * Revision 1.0e: It seems too old version of NVMe specification.  Do you have any special reason to comment the specified 1.0 version instead of 1.3 or something newer? > + *    Chapter 2: Required and optional PCI config registers > + *    Chapter 3: NVMe control registers > + *    Chapter 7.3: Reset behavior > + */ > +static int nvme_disable_and_flr(struct pci_dev *dev, int probe) The name of this function seems able to be started with 'reset_' prefix just like other quirks for reset. What about reset_samsung_pm961 or something? > +{ > + void __iomem *bar; > + u16 cmd; > + u32 cfg; > + > + if (dev->class != PCI_CLASS_STORAGE_EXPRESS || > +     !pcie_has_flr(dev) || !pci_resource_start(dev, 0)) > + return -ENOTTY; > + > + if (probe) > + return 0; > + > + bar = pci_iomap(dev, 0, NVME_REG_CC + sizeof(cfg)); > + if (!bar) > + return -ENOTTY; > + > + pci_read_config_word(dev, PCI_COMMAND, &cmd); > + pci_write_config_word(dev, PCI_COMMAND, cmd | PCI_COMMAND_MEMORY); > + > + cfg = readl(bar + NVME_REG_CC); > + > + /* Disable controller if enabled */ > + if (cfg & NVME_CC_ENABLE) { > + u64 cap = readq(bar + NVME_REG_CAP); > + unsigned long timeout; > + > + /* > +  * Per nvme_disable_ctrl() skip shutdown notification as it > +  * could complete commands to the admin queue.  We only > intend > +  * to quiesce the device before reset. > +  */ > + cfg &= ~(NVME_CC_SHN_MASK | NVME_CC_ENABLE); > + > + writel(cfg, bar + NVME_REG_CC); > + > + /* > +  * Some controllers require an additional delay here, see > +  * NVME_QUIRK_DELAY_BEFORE_CHK_RDY.  None of those are yet > +  * supported by this quirk. > +  */ > + > + /* Cap register provides max timeout in 500ms increments */ > + timeout = ((NVME_CAP_TIMEOUT(cap) + 1) * HZ / 2) + jiffies; > + > + for (;;) { > + u32 status = readl(bar + NVME_REG_CSTS); > + > + /* Ready status becomes zero on disable complete */ > + if (!(status & NVME_CSTS_RDY)) > + break; > + > + msleep(100); > + > + if (time_after(jiffies, timeout)) { > + pci_warn(dev, "Timeout waiting for NVMe ready > status to clear after disable\n"); > + break; > + } > + } > + } > + > + pci_iounmap(dev, bar); > + > + pcie_flr(dev); > + > + return 0; > +} > + >  static const struct pci_dev_reset_methods pci_dev_reset_methods[] = { >   { PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82599_SFP_VF, >    reset_intel_82599_sfp_virtfn }, > @@ -3676,6 +3758,7 @@ static const struct pci_dev_reset_methods > pci_dev_reset_methods[] = { >   reset_ivb_igd }, >   { PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_IVB_M2_VGA, >   reset_ivb_igd }, > + { PCI_VENDOR_ID_SAMSUNG, 0xa804, nvme_disable_and_flr }, Why don't we just define a macro just like other DEVICE_IDs. (e.g. PCIE_DEVICE_ID_INTEL_82599_SFP_VF). #define PCI_DEVICE_ID_SAMSUNG_PM961  0xa804 >   { PCI_VENDOR_ID_CHELSIO, PCI_ANY_ID, >   reset_chelsio_generic_dev }, >   { 0 } > > > _______________________________________________ > Linux-nvme mailing list > Linux-nvme@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-nvme