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.
>
>> 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.
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
