by Marc Zyngier

[permalink] [raw]

Subject: Re: [PATCH v9 3/4] irqchip:create irq domain for each mbigen device

On 16/12/15 14:57, majun wrote:
> Hi Marc and Mark:
>
> On 2015/12/11 10:42, Mark Rutland wrote:
>> On Mon, Nov 23, 2015 at 11:15:12AM +0800, MaJun wrote:
>>> From: Ma Jun <[email protected]>
>>>
>>> For peripheral devices which connect to mbigen,mbigen is a interrupt
>>> controller. So, we create irq domain for each mbigen device and add
>>> mbigen irq domain into irq hierarchy structure.
>>>
>>> Signed-off-by: Ma Jun <[email protected]>
>>> ---
>>> drivers/irqchip/irq-mbigen.c | 119 ++++++++++++++++++++++++++++++++++++++++++
>>> 1 files changed, 119 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/irqchip/irq-mbigen.c b/drivers/irqchip/irq-mbigen.c
>>> index 9f036c2..81ae61f 100644
>>> --- a/drivers/irqchip/irq-mbigen.c
>>> +++ b/drivers/irqchip/irq-mbigen.c
>>> @@ -16,13 +16,36 @@
>>> * along with this program. If not, see <http://www.gnu.org/licenses/>.
>>> */
>>>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/irqchip.h>
>>> #include <linux/module.h>
>>> +#include <linux/msi.h>
>>> #include <linux/of_address.h>
>>> #include <linux/of_irq.h>
>>> #include <linux/of_platform.h>
>>> #include <linux/platform_device.h>
>>> #include <linux/slab.h>
>>>
>>> +/* Interrupt numbers per mbigen node supported */
>>> +#define IRQS_PER_MBIGEN_NODE 128
>>> +
>>> +/* 64 irqs (Pin0-pin63) are reserved for each mbigen chip */
>>> +#define RESERVED_IRQ_PER_MBIGEN_CHIP 64
>>> +
>>> +/**
>>> + * In mbigen vector register
>>> + * bit[21:12]: event id value
>>> + * bit[11:0]: device id
>>> + */
>>> +#define IRQ_EVENT_ID_SHIFT 12
>>> +#define IRQ_EVENT_ID_MASK 0x3ff
>>> +
>>> +/* register range of each mbigen node */
>>> +#define MBIGEN_NODE_OFFSET 0x1000
>>> +
>>> +/* offset of vector register in mbigen node */
>>> +#define REG_MBIGEN_VEC_OFFSET 0x200
>>> +
>>> /**
>>> * struct mbigen_device - holds the information of mbigen device.
>>> *
>>> @@ -34,10 +57,94 @@ struct mbigen_device {
>>> void __iomem *base;
>>> };
>>>
>>> +static inline unsigned int get_mbigen_vec_reg(irq_hw_number_t hwirq)
>>> +{
>>> + unsigned int nid, pin;
>>> +
>>> + hwirq -= RESERVED_IRQ_PER_MBIGEN_CHIP;
>>> + nid = hwirq / IRQS_PER_MBIGEN_NODE + 1;
>>> + pin = hwirq % IRQS_PER_MBIGEN_NODE;
>>> +
>>> + return pin * 4 + nid * MBIGEN_NODE_OFFSET
>>> + + REG_MBIGEN_VEC_OFFSET;
>>> +}
>>
>> Ok. So your "global" pin id is "global" per mbigen chip.
>
> right.
>
>>
>> I think it may make more sense to have separate nid and pin fields in
>> your interrupt-specifier, e.g. interrupt = <1 3 x> for nid 1, pin 3.
>>
>> That's easier for someone to check against a datasheet that describes
>> the nid and pin rather than the global number space you've come up with,
>> and also makes it impossible to describe the reserved IRQs.
>
> There are no nid and pin fields in our new datasheet now.
> All we can see is hardware pin number.
> So adding nid and pin fields makes the people more confused about using
> mbigen.
>
> Further more, "pin" is not a good variable name. I should name it as
> "pin_offset" or just"offset" to present the interrupt pin offset to mbigen node.
>
>>
>>> +
>>> +static struct irq_chip mbigen_irq_chip = {
>>> + .name = "mbigen-v2",
>>> +};
>>> +
>>> +static void mbigen_write_msg(struct msi_desc *desc, struct msi_msg *msg)
>>> +{
>>> + struct irq_data *d = irq_get_irq_data(desc->irq);
>>> + void __iomem *base = d->chip_data;
>>> + u32 val;
>>> +
>>> + base += get_mbigen_vec_reg(d->hwirq);
>>> + val = readl_relaxed(base);
>>> +
>>> + val &= ~(IRQ_EVENT_ID_MASK << IRQ_EVENT_ID_SHIFT);
>>> + val |= (msg->data << IRQ_EVENT_ID_SHIFT);
>>> +
>>> + writel_relaxed(val, base);
>>> +}
>>> +
>>> +static int mbigen_domain_translate(struct irq_domain *d,
>>> + struct irq_fwspec *fwspec,
>>> + unsigned long *hwirq,
>>> + unsigned int *type)
>>> +{
>>> + if (is_of_node(fwspec->fwnode)) {
>>> + if (fwspec->param_count != 2)
>>> + return -EINVAL;
>>> +
>>> + *hwirq = fwspec->param[0];
>>
>> You should validate the hwirq here. For instance, we never expect a
>> hwirq < RESERVED_IRQ_PER_MBIGEN_CHIP here.
>
> Yes, I also think I need to check the hwirq input value.
> The hwirq should be:
> hwirq > RESERVED_IRQ_PER_MBIGEN_CHIP && hwirq < MAXIMUM_INTERRUPT_NUMBER
>
>>
>>> + *type = fwspec->param[1] & IRQ_TYPE_SENSE_MASK;
>>
>> Don't mask out bits you don't expect to be set. Validate that they
>> aren't set and complain if they are.
>>
>
> I referred Marc's dummy driver when coding this function.
>
> Marc, do you have any different comment about these two parts.

My dummy driver was exactly that: a dummy. It was not meant to be
followed to the letter, but just an example showing how to use a new
API. And given that it didn't handle any interrupt, it really didn't
matter what it did in the translate function.

Here, I think Mark is right, and you should follow his recommendation.

Thanks,

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