Re: [PATCH v4] PCI: dwc: pci-dra7xx: Fix MSI IRQ handling

From: Bjorn Helgaas
Date: Mon Mar 30 2020 - 12:29:53 EST

Next message: Sultan Alsawaf: "[PATCH 0/1] drm/i915: Disable Panel Self Refresh (PSR) by default"
Previous message: Rob Herring: "Re: [PATCH v5 1/3] dt-bindings: mmc: Document the Amlogic Meson SDHC MMC host controller"
In reply to: Lorenzo Pieralisi: "Re: [PATCH v4] PCI: dwc: pci-dra7xx: Fix MSI IRQ handling"
Next in thread: Bjorn Helgaas: "Re: [PATCH v4] PCI: dwc: pci-dra7xx: Fix MSI IRQ handling"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

[+cc Marc, Thomas]

On Fri, Mar 27, 2020 at 03:24:34PM +0530, Vignesh Raghavendra wrote:
> Due an issue with PCIe wrapper around DWC PCIe IP on dra7xx, driver
> needs to ensure that there are no pending MSI IRQ vector set (i.e
> PCIE_MSI_INTR0_STATUS reads 0 at least once) before exiting IRQ handler.
> Else, the dra7xx PCIe wrapper will not register new MSI IRQs even though
> PCIE_MSI_INTR0_STATUS shows IRQs are pending.

I'm not an IRQ guy (real IRQ guys CC'd), but I'm wondering if this is
really a symptom of a problem in the generic DWC IRQ handling, not a
problem in dra7xx itself.

I thought it was sort of standard behavior that a device would not
send a new MSI unless there was a transition from "no status bits set"
to "at least one status bit set". I'm looking at this text from the
PCIe r5.0 spec, sec 6.7.3.4:

If the Port is enabled for edge-triggered interrupt signaling using
MSI or MSI-X, an interrupt message must be sent every time the
logical AND of the following conditions transitions from FALSE to
TRUE:

- The associated vector is unmasked (not applicable if MSI does
not support PVM).

- The Hot-Plug Interrupt Enable bit in the Slot Control register
is set to 1b.

- At least one hot-plug event status bit in the Slot Status
register and its associated enable bit in the Slot Control
register are both set to 1b.

and this related commit: https://git.kernel.org/linus/fad214b0aa72

> Therefore its no longer possible to use default IRQ handler provided by
> DWC library. So, add irqchip implementation inside pci-dra7xx.c and
> install new MSI IRQ handler to handle above errata.
>
> This fixes a bug, where PCIe wifi cards with 4 DMA queues like Intel
> 8260 used to throw following error and stall during ping/iperf3 tests.
>
> [ 97.776310] iwlwifi 0000:01:00.0: Queue 9 stuck for 2500 ms.
>
> Signed-off-by: Vignesh Raghavendra <vigneshr@xxxxxx>
> Acked-by: Kishon Vijay Abraham I <kishon@xxxxxx>
> Tested-by: Kishon Vijay Abraham I <kishon@xxxxxx>
> ---
>
> v4:
> Simplify dra7xx_pcie_handle_msi_irq() by spliting inner loop into
> separte function as suggested by Lorenzo
>
> v3:
> - Move loop to service all MSI IRQs into dra7xx_pcie_handle_msi_irq()
> - Add a warning msg when loop counter overflows
>
>
> drivers/pci/controller/dwc/pci-dra7xx.c | 231 ++++++++++++++++++++----
> 1 file changed, 195 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-dra7xx.c b/drivers/pci/controller/dwc/pci-dra7xx.c
> index 9bf7fa99b103..3b0e58f2de58 100644
> --- a/drivers/pci/controller/dwc/pci-dra7xx.c
> +++ b/drivers/pci/controller/dwc/pci-dra7xx.c
> @@ -215,10 +215,6 @@ static int dra7xx_pcie_host_init(struct pcie_port *pp)
> return 0;
> }
>
> -static const struct dw_pcie_host_ops dra7xx_pcie_host_ops = {
> - .host_init = dra7xx_pcie_host_init,
> -};
> -
> static int dra7xx_pcie_intx_map(struct irq_domain *domain, unsigned int irq,
> irq_hw_number_t hwirq)
> {
> @@ -233,43 +229,77 @@ static const struct irq_domain_ops intx_domain_ops = {
> .xlate = pci_irqd_intx_xlate,
> };
>
> -static int dra7xx_pcie_init_irq_domain(struct pcie_port *pp)
> +static int dra7xx_pcie_handle_msi(struct pcie_port *pp, int index)
> {
> struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> - struct device *dev = pci->dev;
> - struct dra7xx_pcie *dra7xx = to_dra7xx_pcie(pci);
> - struct device_node *node = dev->of_node;
> - struct device_node *pcie_intc_node = of_get_next_child(node, NULL);
> + unsigned long val;
> + int pos, irq;
>
> - if (!pcie_intc_node) {
> - dev_err(dev, "No PCIe Intc node found\n");
> - return -ENODEV;
> - }
> + val = dw_pcie_readl_dbi(pci, PCIE_MSI_INTR0_STATUS +
> + (index * MSI_REG_CTRL_BLOCK_SIZE));
> + if (!val)
> + return 0;
>
> - dra7xx->irq_domain = irq_domain_add_linear(pcie_intc_node, PCI_NUM_INTX,
> - &intx_domain_ops, pp);
> - of_node_put(pcie_intc_node);
> - if (!dra7xx->irq_domain) {
> - dev_err(dev, "Failed to get a INTx IRQ domain\n");
> - return -ENODEV;
> + pos = find_next_bit(&val, MAX_MSI_IRQS_PER_CTRL, 0);
> + while (pos != MAX_MSI_IRQS_PER_CTRL) {
> + irq = irq_find_mapping(pp->irq_domain,
> + (index * MAX_MSI_IRQS_PER_CTRL) + pos);
> + generic_handle_irq(irq);
> + pos++;
> + pos = find_next_bit(&val, MAX_MSI_IRQS_PER_CTRL, pos);
> }
>
> - return 0;
> + return 1;
> }
>
> -static irqreturn_t dra7xx_pcie_msi_irq_handler(int irq, void *arg)
> +static void dra7xx_pcie_handle_msi_irq(struct pcie_port *pp)
> {
> - struct dra7xx_pcie *dra7xx = arg;
> - struct dw_pcie *pci = dra7xx->pci;
> - struct pcie_port *pp = &pci->pp;
> + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> + int ret, i, count, num_ctrls;
> +
> + num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
> +
> + /**
> + * Need to make sure all MSI status bits read 0 before exiting.
> + * Else, new MSI IRQs are not registered by the wrapper. Have an
> + * upperbound for the loop and exit the IRQ in case of IRQ flood
> + * to avoid locking up system in interrupt context.
> + */
> + count = 0;
> + do {
> + ret = 0;
> +
> + for (i = 0; i < num_ctrls; i++)
> + ret |= dra7xx_pcie_handle_msi(pp, i);
> + count++;
> + } while (ret && count <= 1000);
> +
> + if (count > 1000)
> + dev_warn_ratelimited(pci->dev,
> + "Too many MSI IRQs to handle\n");
> +}
> +
> +static void dra7xx_pcie_msi_irq_handler(struct irq_desc *desc)
> +{
> + struct irq_chip *chip = irq_desc_get_chip(desc);
> + struct dra7xx_pcie *dra7xx;
> + struct dw_pcie *pci;
> + struct pcie_port *pp;
> unsigned long reg;
> u32 virq, bit;
>
> + chained_irq_enter(chip, desc);
> +
> + pp = irq_desc_get_handler_data(desc);
> + pci = to_dw_pcie_from_pp(pp);
> + dra7xx = to_dra7xx_pcie(pci);
> +
> reg = dra7xx_pcie_readl(dra7xx, PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI);
> + dra7xx_pcie_writel(dra7xx, PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI, reg);
>
> switch (reg) {
> case MSI:
> - dw_handle_msi_irq(pp);
> + dra7xx_pcie_handle_msi_irq(pp);
> break;
> case INTA:
> case INTB:
> @@ -283,9 +313,7 @@ static irqreturn_t dra7xx_pcie_msi_irq_handler(int irq, void *arg)
> break;
> }
>
> - dra7xx_pcie_writel(dra7xx, PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI, reg);
> -
> - return IRQ_HANDLED;
> + chained_irq_exit(chip, desc);
> }
>
> static irqreturn_t dra7xx_pcie_irq_handler(int irq, void *arg)
> @@ -347,6 +375,145 @@ static irqreturn_t dra7xx_pcie_irq_handler(int irq, void *arg)
> return IRQ_HANDLED;
> }
>
> +static int dra7xx_pcie_init_irq_domain(struct pcie_port *pp)
> +{
> + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> + struct device *dev = pci->dev;
> + struct dra7xx_pcie *dra7xx = to_dra7xx_pcie(pci);
> + struct device_node *node = dev->of_node;
> + struct device_node *pcie_intc_node = of_get_next_child(node, NULL);
> +
> + if (!pcie_intc_node) {
> + dev_err(dev, "No PCIe Intc node found\n");
> + return -ENODEV;
> + }
> +
> + irq_set_chained_handler_and_data(pp->irq, dra7xx_pcie_msi_irq_handler,
> + pp);
> + dra7xx->irq_domain = irq_domain_add_linear(pcie_intc_node, PCI_NUM_INTX,
> + &intx_domain_ops, pp);
> + of_node_put(pcie_intc_node);
> + if (!dra7xx->irq_domain) {
> + dev_err(dev, "Failed to get a INTx IRQ domain\n");
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
> +
> +static void dra7xx_pcie_setup_msi_msg(struct irq_data *d, struct msi_msg *msg)
> +{
> + struct pcie_port *pp = irq_data_get_irq_chip_data(d);
> + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> + u64 msi_target;
> +
> + msi_target = (u64)pp->msi_data;
> +
> + msg->address_lo = lower_32_bits(msi_target);
> + msg->address_hi = upper_32_bits(msi_target);
> +
> + msg->data = d->hwirq;
> +
> + dev_dbg(pci->dev, "msi#%d address_hi %#x address_lo %#x\n",
> + (int)d->hwirq, msg->address_hi, msg->address_lo);
> +}
> +
> +static int dra7xx_pcie_msi_set_affinity(struct irq_data *d,
> + const struct cpumask *mask,
> + bool force)
> +{
> + return -EINVAL;
> +}
> +
> +static void dra7xx_pcie_bottom_mask(struct irq_data *d)
> +{
> + struct pcie_port *pp = irq_data_get_irq_chip_data(d);
> + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> + unsigned int res, bit, ctrl;
> + unsigned long flags;
> +
> + raw_spin_lock_irqsave(&pp->lock, flags);
> +
> + ctrl = d->hwirq / MAX_MSI_IRQS_PER_CTRL;
> + res = ctrl * MSI_REG_CTRL_BLOCK_SIZE;
> + bit = d->hwirq % MAX_MSI_IRQS_PER_CTRL;
> +
> + pp->irq_mask[ctrl] |= BIT(bit);
> + dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_MASK + res,
> + pp->irq_mask[ctrl]);
> +
> + raw_spin_unlock_irqrestore(&pp->lock, flags);
> +}
> +
> +static void dra7xx_pcie_bottom_unmask(struct irq_data *d)
> +{
> + struct pcie_port *pp = irq_data_get_irq_chip_data(d);
> + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> + unsigned int res, bit, ctrl;
> + unsigned long flags;
> +
> + raw_spin_lock_irqsave(&pp->lock, flags);
> +
> + ctrl = d->hwirq / MAX_MSI_IRQS_PER_CTRL;
> + res = ctrl * MSI_REG_CTRL_BLOCK_SIZE;
> + bit = d->hwirq % MAX_MSI_IRQS_PER_CTRL;
> +
> + pp->irq_mask[ctrl] &= ~BIT(bit);
> + dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_MASK + res,
> + pp->irq_mask[ctrl]);
> +
> + raw_spin_unlock_irqrestore(&pp->lock, flags);
> +}
> +
> +static void dra7xx_pcie_bottom_ack(struct irq_data *d)
> +{
> + struct pcie_port *pp = irq_data_get_irq_chip_data(d);
> + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> + unsigned int res, bit, ctrl;
> +
> + ctrl = d->hwirq / MAX_MSI_IRQS_PER_CTRL;
> + res = ctrl * MSI_REG_CTRL_BLOCK_SIZE;
> + bit = d->hwirq % MAX_MSI_IRQS_PER_CTRL;
> +
> + dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_STATUS + res, BIT(bit));
> +}
> +
> +static struct irq_chip dra7xx_pci_msi_bottom_irq_chip = {
> + .name = "DRA7XX-PCI-MSI",
> + .irq_ack = dra7xx_pcie_bottom_ack,
> + .irq_compose_msi_msg = dra7xx_pcie_setup_msi_msg,
> + .irq_set_affinity = dra7xx_pcie_msi_set_affinity,
> + .irq_mask = dra7xx_pcie_bottom_mask,
> + .irq_unmask = dra7xx_pcie_bottom_unmask,
> +};
> +
> +static int dra7xx_pcie_msi_host_init(struct pcie_port *pp)
> +{
> + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> + u32 ctrl, num_ctrls;
> +
> + pp->msi_irq_chip = &dra7xx_pci_msi_bottom_irq_chip;
> +
> + num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
> + /* Initialize IRQ Status array */
> + for (ctrl = 0; ctrl < num_ctrls; ctrl++) {
> + pp->irq_mask[ctrl] = ~0;
> + dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_MASK +
> + (ctrl * MSI_REG_CTRL_BLOCK_SIZE),
> + pp->irq_mask[ctrl]);
> + dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_ENABLE +
> + (ctrl * MSI_REG_CTRL_BLOCK_SIZE),
> + ~0);
> + }
> +
> + return dw_pcie_allocate_domains(pp);
> +}
> +
> +static const struct dw_pcie_host_ops dra7xx_pcie_host_ops = {
> + .host_init = dra7xx_pcie_host_init,
> + .msi_host_init = dra7xx_pcie_msi_host_init,
> +};
> +
> static void dra7xx_pcie_ep_init(struct dw_pcie_ep *ep)
> {
> struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> @@ -467,14 +634,6 @@ static int __init dra7xx_add_pcie_port(struct dra7xx_pcie *dra7xx,
> return pp->irq;
> }
>
> - ret = devm_request_irq(dev, pp->irq, dra7xx_pcie_msi_irq_handler,
> - IRQF_SHARED | IRQF_NO_THREAD,
> - "dra7-pcie-msi", dra7xx);
> - if (ret) {
> - dev_err(dev, "failed to request irq\n");
> - return ret;
> - }
> -
> ret = dra7xx_pcie_init_irq_domain(pp);
> if (ret < 0)
> return ret;
> --
> 2.26.0
>

Next message: Sultan Alsawaf: "[PATCH 0/1] drm/i915: Disable Panel Self Refresh (PSR) by default"
Previous message: Rob Herring: "Re: [PATCH v5 1/3] dt-bindings: mmc: Document the Amlogic Meson SDHC MMC host controller"
In reply to: Lorenzo Pieralisi: "Re: [PATCH v4] PCI: dwc: pci-dra7xx: Fix MSI IRQ handling"
Next in thread: Bjorn Helgaas: "Re: [PATCH v4] PCI: dwc: pci-dra7xx: Fix MSI IRQ handling"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]