[PATCH v2 1/2] PCI: Xilinx NWL: Modifying irq chip for legacy interrupts

[PATCH v2 1/2] PCI: Xilinx NWL: Modifying irq chip for legacy interrupts

[Bharat Kumar Gogada]

- 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
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.

Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com>
---
 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);
+}
+
+static void nwl_unmask_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);
+}
+
+static struct irq_chip nwl_leg_irq_chip = {
+	.name = "nwl_pcie:legacy",
+	.irq_enable = nwl_unmask_leg_irq,
+	.irq_disable = nwl_mask_leg_irq,
+	.irq_mask = nwl_mask_leg_irq,
+	.irq_unmask = nwl_unmask_leg_irq,
+};
+
 static int nwl_legacy_map(struct irq_domain *domain, unsigned int irq,
 			  irq_hw_number_t hwirq)
 {
-	irq_set_chip_and_handler(irq, &dummy_irq_chip, handle_simple_irq);
+	irq_set_chip_and_handler(irq, &nwl_leg_irq_chip, handle_level_irq);
 	irq_set_chip_data(irq, domain->host_data);
 
 	return 0;
-- 
2.1.1

[PATCH v2 2/2] PCI: Xilinx NWL: Fix, proc interrupts for legacy virtual irq shown as edge

[Bharat Kumar Gogada]

- Legacy interrupts are level triggered, virtual irq line of End
Point shows as edge in /proc/interrupts.
- Setting irq flags of virtual irq line of EP to level triggered
at the time of mapping.

Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com>
---
 drivers/pci/host/pcie-xilinx-nwl.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/host/pcie-xilinx-nwl.c b/drivers/pci/host/pcie-xilinx-nwl.c
index 6ac3e1d..1cddd1f 100644
--- a/drivers/pci/host/pcie-xilinx-nwl.c
+++ b/drivers/pci/host/pcie-xilinx-nwl.c
@@ -434,6 +434,7 @@ static int nwl_legacy_map(struct irq_domain *domain, unsigned int irq,
 {
 	irq_set_chip_and_handler(irq, &nwl_leg_irq_chip, handle_level_irq);
 	irq_set_chip_data(irq, domain->host_data);
+	irq_set_status_flags(irq, IRQ_LEVEL);
 
 	return 0;
 }
-- 
2.1.1

Re: [PATCH v2 1/2] PCI: Xilinx NWL: Modifying irq chip for legacy interrupts

[Marc Zyngier]

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@xilinx.com>
> ---
>  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?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

Re: [PATCH v2 2/2] PCI: Xilinx NWL: Fix, proc interrupts for legacy virtual irq shown as edge

[Marc Zyngier]

On 25/01/17 08:52, Bharat Kumar Gogada wrote:
> - Legacy interrupts are level triggered, virtual irq line of End
> Point shows as edge in /proc/interrupts.
> - Setting irq flags of virtual irq line of EP to level triggered
> at the time of mapping.
> 
> Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com>
> ---
>  drivers/pci/host/pcie-xilinx-nwl.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/host/pcie-xilinx-nwl.c b/drivers/pci/host/pcie-xilinx-nwl.c
> index 6ac3e1d..1cddd1f 100644
> --- a/drivers/pci/host/pcie-xilinx-nwl.c
> +++ b/drivers/pci/host/pcie-xilinx-nwl.c
> @@ -434,6 +434,7 @@ static int nwl_legacy_map(struct irq_domain *domain, unsigned int irq,
>  {
>  	irq_set_chip_and_handler(irq, &nwl_leg_irq_chip, handle_level_irq);
>  	irq_set_chip_data(irq, domain->host_data);
> +	irq_set_status_flags(irq, IRQ_LEVEL);
>  
>  	return 0;
>  }
> 

As said in my previous review [1], this should be folded in the previous
patch, as it doesn't make much sense on its own.

Thanks,

	M.

[1] http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1316912.html
-- 
Jazz is not dead. It just smells funny...

RE: [PATCH v2 1/2] PCI: Xilinx NWL: Modifying irq chip for legacy interrupts

[Bharat Kumar Gogada]

> 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@xilinx.com>
> > ---
> >  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.

RE: [PATCH v2 2/2] PCI: Xilinx NWL: Fix, proc interrupts for legacy virtual irq shown as edge

[Bharat Kumar Gogada]

> 
> On 25/01/17 08:52, Bharat Kumar Gogada wrote:
> > - Legacy interrupts are level triggered, virtual irq line of End Point
> > shows as edge in /proc/interrupts.
> > - Setting irq flags of virtual irq line of EP to level triggered at
> > the time of mapping.
> >
> > Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com>
> > ---
> >  drivers/pci/host/pcie-xilinx-nwl.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/pci/host/pcie-xilinx-nwl.c
> > b/drivers/pci/host/pcie-xilinx-nwl.c
> > index 6ac3e1d..1cddd1f 100644
> > --- a/drivers/pci/host/pcie-xilinx-nwl.c
> > +++ b/drivers/pci/host/pcie-xilinx-nwl.c
> > @@ -434,6 +434,7 @@ static int nwl_legacy_map(struct irq_domain
> > *domain, unsigned int irq,  {
> >  	irq_set_chip_and_handler(irq, &nwl_leg_irq_chip, handle_level_irq);
> >  	irq_set_chip_data(irq, domain->host_data);
> > +	irq_set_status_flags(irq, IRQ_LEVEL);
> >
> >  	return 0;
> >  }
> >
> 
> As said in my previous review [1], this should be folded in the previous patch, as
> it doesn't make much sense on its own.
> 
Agreed, will send in same previous patch. 

bharat