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SubjectRe: [PATCH v2 2/9] PCI: keystone: Modify legacy_irq_handler to check the IRQ_STATUS of INTA/B/C/D
In the subject, "legacy_irq_handler" looks like it's supposed to be a
function name, but it's not. Maybe something like:

PCI: keystone: Check INTA/B/C/D IRQ_STATUS in ks_pcie_legacy_irq_handler()

On Thu, Feb 07, 2019 at 04:39:17PM +0530, Kishon Vijay Abraham I wrote:
> The legacy interrupt handler directly checks the IRQ_STATUS register
> corresponding to a interrupt line inorder to invoke generic_handle_irq.

s/The legacy interrupt handler/ks_pcie_handle_legacy_irq()/ ?
s/to a/to an/
s/inorder/in order/
s/generic_handle_irq/generic_handle_irq()/

> While this is okay for K2G platform which has separate interrupt line for
> each of the 4 legacy interrupts, AM654 which uses the same PCIe wrapper
> has a single interrupt line for all the legacy interrupts. So for AM654
> the interrupt handler won't be able to directly check the IRQ_STATUS
> register corresponding to the interrupt line.

s/platform which/platform, which/
s/separate interrupt line/separate interrupt lines/
s/AM654 which/AM654, which/
s/PCIe wrapper/PCIe wrapper,/
s/interrupt line for all/interrupt line shared by all/


> Also the legacy interrupt handler uses 'virq' obtained from
> irq_of_parse_and_map to find the correct interrupt line which raised the
> interrupt. There is no guarantee that virq assigned for contiguous hardware
> irq will be contiguous and the interrupt handler might end up checking
> the wrong IRQ_STATUS register.

s/irq_of_parse_and_map/irq_of_parse_and_map()
s/irq will/IRQ will/

> In order to overcome the above issues, read the IRQ_STATUS register of
> all the 4 legacy interrupts to determine which interrupt was raised.
>
> Link: https://lkml.kernel.org/r/bb081d21-7c03-0357-4294-7e92d95d838c@arm.com
> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> ---
> drivers/pci/controller/dwc/pci-keystone.c | 22 ++++++++++++----------
> 1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-keystone.c b/drivers/pci/controller/dwc/pci-keystone.c
> index 5286a480f76b..4cf9849d5a1d 100644
> --- a/drivers/pci/controller/dwc/pci-keystone.c
> +++ b/drivers/pci/controller/dwc/pci-keystone.c
> @@ -214,16 +214,11 @@ static void ks_pcie_handle_legacy_irq(struct keystone_pcie *ks_pcie,
> {
> struct dw_pcie *pci = ks_pcie->pci;
> struct device *dev = pci->dev;
> - u32 pending;
> int virq;
>
> - pending = ks_pcie_app_readl(ks_pcie, IRQ_STATUS(offset));
> -
> - if (BIT(0) & pending) {
> - virq = irq_linear_revmap(ks_pcie->legacy_irq_domain, offset);
> - dev_dbg(dev, ": irq: irq_offset %d, virq %d\n", offset, virq);
> - generic_handle_irq(virq);
> - }
> + virq = irq_linear_revmap(ks_pcie->legacy_irq_domain, offset);
> + dev_dbg(dev, ": irq: irq_offset %d, virq %d\n", offset, virq);
> + generic_handle_irq(virq);
>
> /* EOI the INTx interrupt */
> ks_pcie_app_writel(ks_pcie, IRQ_EOI, offset);
> @@ -607,8 +602,9 @@ static void ks_pcie_legacy_irq_handler(struct irq_desc *desc)
> struct keystone_pcie *ks_pcie = irq_desc_get_handler_data(desc);
> struct dw_pcie *pci = ks_pcie->pci;
> struct device *dev = pci->dev;
> - u32 irq_offset = irq - ks_pcie->legacy_host_irqs[0];
> struct irq_chip *chip = irq_desc_get_chip(desc);
> + unsigned int irq_no;
> + u32 reg;
>
> dev_dbg(dev, ": Handling legacy irq %d\n", irq);
>
> @@ -618,7 +614,13 @@ static void ks_pcie_legacy_irq_handler(struct irq_desc *desc)
> * ack operation.
> */
> chained_irq_enter(chip, desc);
> - ks_pcie_handle_legacy_irq(ks_pcie, irq_offset);
> + for (irq_no = 0; irq_no < PCI_NUM_INTX; irq_no++) {
> + reg = ks_pcie_app_readl(ks_pcie, IRQ_STATUS(irq_no));
> + if (!(reg & INTx_EN))
> + continue;
> + ks_pcie_handle_legacy_irq(ks_pcie, irq_no);

It's too bad that reading IRQ_STATUS and writing IRQ_EOI are now in
separate functions. It's nice to have them together for code auditing
purposes.

Could maybe accumulate a mask of which INTx bits are set and call
ks_pcie_handle_legacy_irq() only once with that mask? Of course, then
you'd need another loop in ks_pcie_handle_legacy_irq().

> + }
> +
> chained_irq_exit(chip, desc);
> }
>
> --
> 2.17.1
>

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