Re: [PATCH] irqchip/irq-csky-mpintc: Add triger type and priority setting

[Marc Zyngier]

On 18/01/2019 06:28, Guo Ren wrote:
> Thx Marc,
> 
> On Thu, Jan 17, 2019 at 05:17:45PM +0000, Marc Zyngier wrote:
>> Hi Guo,
>>
>> On 15/01/2019 16:36, guoren@xxxxxxxxxx wrote:
>>> From: Guo Ren <ren_guo@xxxxxxxxx>
>>>
>>> Support 4 triger types:
>>>  - IRQ_TYPE_LEVEL_HIGH
>>>  - IRQ_TYPE_LEVEL_LOW
>>>  - IRQ_TYPE_EDGE_RISING
>>>  - IRQ_TYPE_EDGE_FALLING
>>>
>>> Support 0-255 priority setting for each irq.
>>>
>>> Signed-off-by: Guo Ren <ren_guo@xxxxxxxxx>
>>> ---
>>>  .../bindings/interrupt-controller/csky,mpintc.txt  | 24 ++++++-
>>>  drivers/irqchip/irq-csky-mpintc.c                  | 78 +++++++++++++++++++++-
>>>  2 files changed, 99 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/interrupt-controller/csky,mpintc.txt b/Documentation/devicetree/bindings/interrupt-controller/csky,mpintc.txt
>>> index ab921f1..364b789 100644
>>> --- a/Documentation/devicetree/bindings/interrupt-controller/csky,mpintc.txt
>>> +++ b/Documentation/devicetree/bindings/interrupt-controller/csky,mpintc.txt
>>> @@ -11,6 +11,14 @@ Interrupt number definition:
>>>   16-31  : private  irq, and we use 16 as the co-processor timer.
>>>   31-1024: common irq for soc ip.
>>>  
>>> +Interrupt triger mode:
>>> +  IRQ_TYPE_LEVEL_HIGH (default)
>>> +  IRQ_TYPE_LEVEL_LOW
>>> +  IRQ_TYPE_EDGE_RISING
>>> +  IRQ_TYPE_EDGE_FALLING
>>> +
>>> +Interrupt priority range: 0-255
>>> +
>>>  =============================
>>>  intc node bindings definition
>>>  =============================
>>> @@ -26,7 +34,7 @@ intc node bindings definition
>>>  	- #interrupt-cells
>>>  		Usage: required
>>>  		Value type: <u32>
>>> -		Definition: must be <1>
>>> +		Definition: could be <1> or <2>
>>>  	- interrupt-controller:
>>>  		Usage: required
>>>  
>>> @@ -35,6 +43,18 @@ Examples:
>>>  
>>>  	intc: interrupt-controller {
>>>  		compatible = "csky,mpintc";
>>> -		#interrupt-cells = <1>;
>>> +		#interrupt-cells = <2>;
>>>  		interrupt-controller;
>>>  	};
>>> +
>>> +	0: device-example {
>>> +		...
>>> +		interrupts = <33 IRQ_TYPE_EDGE_RISING>;
>>> +		interrupt-parent = <&intc>;
>>> +	};
>>> +
>>> +	1: device-example {
>>> +		...
>>> +		interrupts = <34 ((priority << 4) | IRQ_TYPE_EDGE_RISING)>;
>>> +		interrupt-parent = <&intc>;
>>> +	};
>>> diff --git a/drivers/irqchip/irq-csky-mpintc.c b/drivers/irqchip/irq-csky-mpintc.c
>>> index c67c961..9edc6d3 100644
>>> --- a/drivers/irqchip/irq-csky-mpintc.c
>>> +++ b/drivers/irqchip/irq-csky-mpintc.c
>>> @@ -29,9 +29,12 @@ static void __iomem *INTCL_base;
>>>  
>>>  #define INTCG_ICTLR	0x0
>>>  #define INTCG_CICFGR	0x100
>>> +#define INTCG_CIPRTR	0x200
>>>  #define INTCG_CIDSTR	0x1000
>>>  
>>>  #define INTCL_PICTLR	0x0
>>> +#define INTCL_CFGR	0x14
>>> +#define INTCL_PRTR	0x20
>>>  #define INTCL_SIGR	0x60
>>>  #define INTCL_HPPIR	0x68
>>>  #define INTCL_RDYIR	0x6c
>>> @@ -73,6 +76,78 @@ static void csky_mpintc_eoi(struct irq_data *d)
>>>  	writel_relaxed(d->hwirq, reg_base + INTCL_CACR);
>>>  }
>>>  
>>> +static int csky_mpintc_set_type(struct irq_data *d, unsigned int type)
>>> +{
>>> +	unsigned int priority, triger;
>>
>> nit: s/triger/trigger/ everywhere.
> Ok
> 
>>
>>> +	unsigned int offset, bit_offset;
>>> +	void __iomem *reg_base;
>>> +
>>> +	/*
>>> +	 * type Bit field: | 32 - 12  |  11 - 4  |   3 - 0    |
>>> +	 *                   reserved   priority   triger type
>>> +	 */
>>> +	triger	 = type & IRQ_TYPE_SENSE_MASK;
>>> +	priority = (type >> 4) & 0xff;
>>
>> Definitely not. The Linux API to set the trigger does not carry any
>> priority information, nor should it. Priorities should be set
>> statically, and no driver should ever be able to change it.
> Currently priority in dts is:
> 
> 	interrupts = <34 ((priority << 4) | IRQ_TYPE_EDGE_RISING)>;
> 
> change it to:
> 
> 	interrupts = <34 IRQ_TYPE_EDGE_RISING priority>;
> 

I don't think you need to change the DT format, as this is quite painful
for users.

> Implement csky own csky_irq_domain_xlate_cells() ...
> 
> int csky_irq_domain_xlate_cells(struct irq_domain *d, struct device_node *ctrlr,
> 			const u32 *intspec, unsigned int intsize,
> 			irq_hw_number_t *out_hwirq, unsigned int *out_type)
> {
> 	if (WARN_ON(intsize < 1))
> 		return -EINVAL;
> 	*out_hwirq = intspec[0];
> 	if (intsize > 1)
> 		*out_type = intspec[1] & IRQ_TYPE_SENSE_MASK;
> 	else
> 		*out_type = IRQ_TYPE_NONE;
> 
> 	if (intsize > 2)
> 		setup_priority(d->hwirq, intspec[2]);

That's still a problem. Linux doesn't expect interrupts to have
different priorities. All interrupts are equal in that respect, and
interrupt nesting is not something we expect.

I'd be more confident if you programmed a default priority at boot time,
and completely ignored the DT information.

> 
> 	return 0;
> }
> Hmm?
> 
>>
>>> +
>>> +	switch (triger) {
>>> +	case IRQ_TYPE_LEVEL_HIGH:
>>> +		triger = 0;
>>> +		break;
>>> +	case IRQ_TYPE_LEVEL_LOW:
>>> +		triger = 1;
>>> +		break;
>>> +	case IRQ_TYPE_EDGE_RISING:
>>> +		triger = 2;
>>> +		break;
>>> +	case IRQ_TYPE_EDGE_FALLING:
>>> +		triger = 3;
>>
>> Can you define some macros that represent these magic values?
> OK.
>>
>>> +		break;
>>> +	default:
>>> +		triger = 0;
>>> +		break;
>>
>> If you get an invalid combination, you shouldn't blindly accept it, but
>> instead return an error.
> OK.
> 
>>
>>> +	}
>>> +
>>> +	if (d->hwirq < COMM_IRQ_BASE) {
>>> +		reg_base = this_cpu_read(intcl_reg);
>>
>> Are you guaranteed to be in a non-preemptible section here? I can see
>> things going wrong if not.
> 
> ???
> In percpu-def.h, I see this_cpu_read is safe() for preemption or
> interrupt.

Sorry, I wasn't clear, see below.

> What's the wrong with preemption?

The problem is that if the driver calls irq_set_type() on a per-CPU
interrupt without preemption being disabled, it can be preempted at any
point and migrated anywhere before the call to this_cpu_read() takes
place. This means you can never know which CPU you've programmed.

One possible approach is to mandate these interrupts to be only changed
in non-preemptible context, which is what the various ARM GICs do for
their per-CPU interrupts.


> 
>>> +
>>> +		if (triger) {
>>> +			offset = ((d->hwirq * 2) / 32) * 4;
>>> +			bit_offset = (d->hwirq * 2) % 32;
>>
>> This needs to be turned into a set of macros so that the non-percpu code
>> can reuse it.
> 
> 
> #define IRQ_OFFSET(irq) \
> 	((irq < COMM_IRQ_BASE) ? irq : irq - COMM_IRQ_BASE) 
> 
> #define TRIG_VAL(trigger, irq) \
> 	(trigger << ((IRQ_OFFSET(irq) * 2) % 32))
> 
> #define TRIG_VAL_MSK(irq) \
> 	(3 << ((IRQ_OFFSET(irq) * 2) % 32))
> 
> #define TRIG_BASE(irq) \
> 	((((IRQ_OFFSET(irq) * 2) / 32) * 4) + \
> 	((irq < COMM_IRQ_BASE) ? this_cpu_read(intcl_reg) : INTCG_base))
> 
> tmp = readl_relaxed(TRIG_BASE(d->hwirq)) & (~TRIG_VAL_MSK(d->hwirq));
> writel_relaxed(tmp | TRIG_VAL(triger, d->hwirq), TRIG_BASE(d->hwirq));
> 
> Hmm?

I was only looking for something that abstract the offsets, such as:

#define BYTE_OFFSET(i) (((i) * 2) / 32) * 4)
#define BIT_OFFSET(i)  ((i) * 2) % 32)

and keep the rest of the structure as is.

Thanks,

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