[PATCH v2 6/7] drm/panfrost: Add support for GPU heap allocations

[Steven Price]

On 25/07/2019 22:11, Rob Herring wrote:
> On Thu, Jul 25, 2019 at 7:08 AM Robin Murphy <robin.murphy at arm.com> wrote:
>>
>> Hi Rob,
>>
>> On 25/07/2019 02:10, Rob Herring wrote:
>> [...]
>>> @@ -328,6 +427,18 @@ static irqreturn_t panfrost_mmu_irq_handler(int irq, void *data)
>>>                access_type = (fault_status >> 8) & 0x3;
>>>                source_id = (fault_status >> 16);
>>>
>>> +             /* Page fault only */
>>> +             if ((status & mask) == BIT(i)) {
>>> +                     WARN_ON(exception_type < 0xC1 || exception_type > 0xC4);
>>> +
>>> +                     ret = panfrost_mmu_map_fault_addr(pfdev, i, addr);
>>> +                     if (!ret) {
>>> +                             mmu_write(pfdev, MMU_INT_CLEAR, BIT(i));
>>> +                             status &= ~mask;
>>> +                             continue;
>>> +                     }
>>> +             }
>>> +
>>>                /* terminal fault, print info about the fault */
>>>                dev_err(pfdev->dev,
>>>                        "Unhandled Page fault in AS%d at VA 0x%016llX\n"
>>> @@ -368,8 +479,9 @@ int panfrost_mmu_init(struct panfrost_device *pfdev)
>>>        if (irq <= 0)
>>>                return -ENODEV;
>>>
>>> -     err = devm_request_irq(pfdev->dev, irq, panfrost_mmu_irq_handler,
>>> -                            IRQF_SHARED, "mmu", pfdev);
>>> +     err = devm_request_threaded_irq(pfdev->dev, irq, NULL,
>>> +                                     panfrost_mmu_irq_handler,
>>> +                                     IRQF_ONESHOT, "mmu", pfdev);
>>
>> The change of flags here breaks platforms using a single shared
>> interrupt line.
> 
> Do they exist? I think this was largely copy-n-paste leftover from the

Good question - of the platforms I know about they all have separate 
IRQs, but kbase does explicitly allow shared interrupts so it's quite 
possible there is a platform out there which does.

> lima driver where utgard has a bunch of irqs and so they get combined.
> While it's possible certainly, I'd like to avoid having to do further
> rework either to use a workqueue or we need a single driver handler
> which then dispatches the sub handlers. The problem is threaded irq
> handlers don't work with shared irqs.

It seems reasonable to me to at least wait until someone identifies a 
platform which needs shared interrupts before embarking on the refactoring.

Steve