> The subject line is not very descriptive. How about "Enforce level
> triggering for legacy interrupts"?
>
> On 25/01/17 08:52, Bharat Kumar Gogada wrote:
> > - Few wifi end points which only support legacy interrupts,
> > performs hardware reset functionalities after disabling interrupts
> > by invoking disable_irq and then re-enable using enable_irq, they
> > enable hardware interrupts first and then virtual irq line later.
> > - The legacy irq line goes low only after DEASSERT_INTx is
> > received.As the legacy irq line is high immediately after hardware
> > interrupts are enabled but virq of EP is still in disabled state
> > and EP handler is never executed resulting no DEASSERT_INTx.If dummy
> > irq chip is used, interrutps are not masked and system is
>
> interrupts
>
> > hanging with CPU stall.
> > - Adding irq chip functions instead of dummy irq chip for legacy
> > interrupts.
> > - Legacy interrupts are level sensitive, so using handle_level_irq
> > is more appropriate as it is masks interrupts until End point handles
> > interrupts and unmasks interrutps after End point handler is executed.
>
> interrupts
>
> >
> > Signed-off-by: Bharat Kumar Gogada <bharatku@xxxxxxxxxx>
> > ---
> > drivers/pci/host/pcie-xilinx-nwl.c | 36
> +++++++++++++++++++++++++++++++++++-
> > 1 file changed, 35 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/host/pcie-xilinx-nwl.c b/drivers/pci/host/pcie-xilinx-
> nwl.c
> > index 43eaa4a..6ac3e1d 100644
> > --- a/drivers/pci/host/pcie-xilinx-nwl.c
> > +++ b/drivers/pci/host/pcie-xilinx-nwl.c
> > @@ -395,10 +395,44 @@ static void nwl_pcie_msi_handler_low(struct
> irq_desc *desc)
> > chained_irq_exit(chip, desc);
> > }
> >
> > +static void nwl_mask_leg_irq(struct irq_data *data)
> > +{
> > + struct irq_desc *desc = irq_to_desc(data->irq);
> > + struct nwl_pcie *pcie;
> > + u32 mask;
> > + u32 val;
> > +
> > + pcie = irq_desc_get_chip_data(desc);
> > + mask = 1 << (data->hwirq - 1);
> > + val = nwl_bridge_readl(pcie, MSGF_LEG_MASK);
> > + nwl_bridge_writel(pcie, (val & (~mask)), MSGF_LEG_MASK);
>
> Oh please! Think of the following:
>
> cpu0 cpu1
> read
> read
> write
> write
>
> How can you make this reliable if you don't have any form of mutual
> exclusion that spans both mask and unmask, and ensures the atomicity of
> the RMW sequence?
>
Agreed, will send with locks.
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