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Message-ID: <bb80062f-28ac-b41c-5d56-90ede82037a2@arm.com>
Date: Fri, 18 Jan 2019 09:32:03 +0000
From: Marc Zyngier <marc.zyngier@....com>
To: Guo Ren <guoren@...nel.org>
Cc: tglx@...utronix.de, jason@...edaemon.net, robh+dt@...nel.org,
mark.rutland@....com, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org, Guo Ren <ren_guo@...ky.com>
Subject: Re: [PATCH] irqchip/irq-csky-mpintc: Add triger type and priority
setting
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@...nel.org wrote:
>>> From: Guo Ren <ren_guo@...ky.com>
>>>
>>> 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@...ky.com>
>>> ---
>>> .../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...
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