On 11/05/2015 07:43 PM, Grygorii Strashko wrote:
> diff --git a/drivers/pci/host/pci-dra7xx.c b/drivers/pci/host/pci-dra7xx.c
> index 6589e7e..31460f4 100644
> --- a/drivers/pci/host/pci-dra7xx.c
> +++ b/drivers/pci/host/pci-dra7xx.c
> @@ -302,8 +302,30 @@ static int __init dra7xx_add_pcie_port(struct
> dra7xx_pcie *dra7xx,
> return -EINVAL;
> }
>
> + /*
> + * Mark dra7xx_pcie_msi IRQ as IRQF_NO_THREAD
> + * On -RT and if kernel is booting with "threadirqs" cmd line parameter
> + * the dra7xx_pcie_msi_irq_handler() will be forced threaded but,
> + * in the same time, it's IRQ dispatcher and calls generic_handle_irq(),
> + * which, in turn, will be resolved to handle_simple_irq() call.
> + * The handle_simple_irq() expected to be called with IRQ disabled, as
> + * result kernle will display warning:
> + * "irq XXX handler YYY+0x0/0x14 enabled interrupts".
> + *
> + * Current DRA7 PCIe hw configuration supports 32 interrupts,
> + * which cannot change because it's hardwired in silicon, and can assume
> + * that only a few (most of the time it will be exactly ONE) of those
> + * interrupts are pending at the same time. So, It's sane way to dial
> + * with above issue by marking dra7xx_pcie_msi IRQ as IRQF_NO_THREAD.
> + * if some platform will utilize a lot of MSI IRQs and will suffer
> + * form -RT latencies degradation because of that - IRQF_NO_THREAD can
> + * be removed and "Warning Annihilation" W/A can be applied [1]
> + *
> + * [1] https://lkml.org/lkml/2015/11/2/578
I don't think this novel is required. Also a reference to a patch which
was not accepted is not a smart idea (since people might think they
will improve their -RT latency by applying it without thinking).
Do you have any *real* numbers where you can say this patch does
better/worse than what you suggester earlier? I'm simply asking because
each gpio-irq multiplexing driver does the same thing.
> + */
> ret = devm_request_irq(&pdev->dev, pp->irq,
> - dra7xx_pcie_msi_irq_handler, IRQF_SHARED,
> + dra7xx_pcie_msi_irq_handler,
> + IRQF_SHARED | IRQF_NO_THREAD,
> "dra7-pcie-msi", pp);
> if (ret) {
> dev_err(&pdev->dev, "failed to request irq\n");
>
Sebastian
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