On Thu, 24 Apr 2025, Jani Nikula <jani.nik...@linux.intel.com> wrote:
>On Thu, 24 Apr 2025, Sebastian Andrzej Siewior <bige...@linutronix.de>
>wrote:
>> On 2025-04-24 14:56:08 [+0800], Junxiao Chang wrote:
>>> MEI GSC interrupt comes from i915. It has top half and bottom half.
>>> Top half is called from i915 interrupt handler. It should be in irq
>>> disabled context.
>>>
>>> With RT kernel, by default i915 IRQ handler is in threaded IRQ. MEI
>>> GSC top half might be in threaded IRQ context. In this case, local
>>> IRQ should be disabled for MEI GSC interrupt top half.
>>>
>>> This change fixes A380/A770 GPU boot hang issue with RT kernel.
>>
>> This should have a Fixes when generic_handle_irq() was introduced.
If PREEMPT_RT is disabled, original driver works fine. I prefer to not
add "Fixes:"?
>>
>>> Signed-off-by: Junxiao Chang <junxiao.ch...@intel.com>
>>> ---
>>> drivers/gpu/drm/i915/gt/intel_gsc.c | 14 ++++++++++++++
>>> 1 file changed, 14 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/i915/gt/intel_gsc.c
>>> b/drivers/gpu/drm/i915/gt/intel_gsc.c
>>> index 1e925c75fb080..9c72117263f78 100644
>>> --- a/drivers/gpu/drm/i915/gt/intel_gsc.c
>>> +++ b/drivers/gpu/drm/i915/gt/intel_gsc.c
>>> @@ -270,6 +270,9 @@ static void gsc_init_one(struct drm_i915_private
>>> *i915, struct intel_gsc *gsc, static void gsc_irq_handler(struct
>>> intel_gt *gt, unsigned int intf_id) {
>>> int ret;
>>> +#ifdef CONFIG_PREEMPT_RT
>>> + int irq_disabled_flag;
>>> +#endif
>>>
>>> if (intf_id >= INTEL_GSC_NUM_INTERFACES) {
>>> gt_warn_once(gt, "GSC irq: intf_id %d is out of range",
>>> intf_id);
>>> @@ -284,7 +287,18 @@ static void gsc_irq_handler(struct intel_gt *gt,
>unsigned int intf_id)
>>> if (gt->gsc.intf[intf_id].irq < 0)
>>> return;
>>>
>>> +#ifdef CONFIG_PREEMPT_RT
>>> + /* mei interrupt top half should run in irq disabled context */
>>> + irq_disabled_flag = irqs_disabled();
>>> + if (!irq_disabled_flag)
>>> + local_irq_disable();
>>> +#endif
>>> ret = generic_handle_irq(gt->gsc.intf[intf_id].irq);
>>
>> What about generic_handle_irq_safe() instead the whole ifdef show?
>
>Anything without the ifdefs would be welcome.
Sebastain's suggestion looks very good. I just tried it, it works well with
both RT and non RT, it doesn't need ifdefs. I will do more testing.
>BR,
>Jani.
>
>>
>>> +#ifdef CONFIG_PREEMPT_RT
>>> + if (!irq_disabled_flag)
>>> + local_irq_enable();
>>> +#endif
>>> +
>>> if (ret)
>>> gt_err_ratelimited(gt, "error handling GSC irq: %d\n", ret); }
>>
>> Sebastian
>
>--
>Jani Nikula, Intel
Thanks!
Junxiao
