On Tue, Sep 03, 2024 at 10:55:44AM +0800, Kai-Heng Feng wrote: > Meteor Lake VMD has a bug that the IRQ raises before the DMA region is > ready, so the requested IO is considered never completed: > [ 97.343423] nvme nvme0: I/O 259 QID 2 timeout, completion polled > [ 97.343446] nvme nvme0: I/O 384 QID 3 timeout, completion polled > [ 97.343459] nvme nvme0: I/O 320 QID 4 timeout, completion polled > [ 97.343470] nvme nvme0: I/O 707 QID 5 timeout, completion polled > > The is documented as erratum MTL016 [0]. The suggested workaround is to > "The VMD MSI interrupt-handler should initially perform a dummy register > read to the MSI initiator device prior to any writes to ensure proper > PCIe ordering." which essentially is adding a delay before the interrupt > handling. > Why can't you add a dummy register read instead? Adding a delay for PCIe ordering is not going to work always. > Hence add a delay before handle interrupt to workaround the erratum. > > [0] https://edc.intel.com/content/www/us/en/design/products/platforms/details/meteor-lake-u-p/core-ultra-processor-specification-update/errata-details/#MTL016 > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=217871 > Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> > --- > drivers/pci/controller/vmd.c | 18 ++++++++++++++++-- > 1 file changed, 16 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c > index a726de0af011..3433b3730f9c 100644 > --- a/drivers/pci/controller/vmd.c > +++ b/drivers/pci/controller/vmd.c > @@ -16,6 +16,7 @@ > #include <linux/srcu.h> > #include <linux/rculist.h> > #include <linux/rcupdate.h> > +#include <linux/delay.h> > > #include <asm/irqdomain.h> > > @@ -74,6 +75,9 @@ enum vmd_features { > * proper power management of the SoC. > */ > VMD_FEAT_BIOS_PM_QUIRK = (1 << 5), > + > + /* Erratum MTL016 */ > + VMD_FEAT_INTERRUPT_QUIRK = (1 << 6), > }; > > #define VMD_BIOS_PM_QUIRK_LTR 0x1003 /* 3145728 ns */ > @@ -90,6 +94,8 @@ static DEFINE_IDA(vmd_instance_ida); > */ > static DEFINE_RAW_SPINLOCK(list_lock); > > +static bool interrupt_delay; > + > /** > * struct vmd_irq - private data to map driver IRQ to the VMD shared vector > * @node: list item for parent traversal. > @@ -105,6 +111,7 @@ struct vmd_irq { > struct vmd_irq_list *irq; > bool enabled; > unsigned int virq; > + bool delay_irq; This is unused. Perhaps you wanted to use this instead of interrupt_delay? - Mani > }; > > /** > @@ -680,8 +687,11 @@ static irqreturn_t vmd_irq(int irq, void *data) > int idx; > > idx = srcu_read_lock(&irqs->srcu); > - list_for_each_entry_rcu(vmdirq, &irqs->irq_list, node) > + list_for_each_entry_rcu(vmdirq, &irqs->irq_list, node) { > + if (interrupt_delay) > + udelay(4); > generic_handle_irq(vmdirq->virq); > + } > srcu_read_unlock(&irqs->srcu, idx); > > return IRQ_HANDLED; > @@ -1015,6 +1025,9 @@ static int vmd_probe(struct pci_dev *dev, const struct pci_device_id *id) > if (features & VMD_FEAT_OFFSET_FIRST_VECTOR) > vmd->first_vec = 1; > > + if (features & VMD_FEAT_INTERRUPT_QUIRK) > + interrupt_delay = true; > + > spin_lock_init(&vmd->cfg_lock); > pci_set_drvdata(dev, vmd); > err = vmd_enable_domain(vmd, features); > @@ -1106,7 +1119,8 @@ static const struct pci_device_id vmd_ids[] = { > {PCI_VDEVICE(INTEL, 0xa77f), > .driver_data = VMD_FEATS_CLIENT,}, > {PCI_VDEVICE(INTEL, 0x7d0b), > - .driver_data = VMD_FEATS_CLIENT,}, > + .driver_data = VMD_FEATS_CLIENT | > + VMD_FEAT_INTERRUPT_QUIRK,}, > {PCI_VDEVICE(INTEL, 0xad0b), > .driver_data = VMD_FEATS_CLIENT,}, > {PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_VMD_9A0B), > -- > 2.43.0 > -- மணிவண்ணன் சதாசிவம்
