usb: dwc3: gadget: Prevent irq storm when TH re-executes

commit 69c58dee upstream.

While commit d325a1de ("usb: dwc3: gadget: Prevent losing events in
event cache") makes sure that top half(TH) does not end up overwriting the
cached events before processing them when the TH gets invoked more than one
time, returning IRQ_HANDLED results in occasional irq storm where the TH
hogs the CPU. The irq storm can be prevented by the flag before event
handler busy is cleared. Default enable interrupt moderation in all
versions which support them.

ftrace event stub during dwc3 irq storm:
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000866: irq_handler_exit: irq=14 ret=handled
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000872: irq_handler_entry: irq=504 name=dwc3
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000874: irq_handler_exit: irq=504 ret=handled
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000881: irq_handler_entry: irq=504 name=dwc3
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000883: irq_handler_exit: irq=504 ret=handled
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000889: irq_handler_entry: irq=504 name=dwc3
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000892: irq_handler_exit: irq=504 ret=handled
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000898: irq_handler_entry: irq=504 name=dwc3
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000901: irq_handler_exit: irq=504 ret=handled
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000907: irq_handler_entry: irq=504 name=dwc3
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000909: irq_handler_exit: irq=504 ret=handled
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000915: irq_handler_entry: irq=504 name=dwc3
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000918: irq_handler_exit: irq=504 ret=handled
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000924: irq_handler_entry: irq=504 name=dwc3
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000927: irq_handler_exit: irq=504 ret=handled
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000933: irq_handler_entry: irq=504 name=dwc3
    irq/504_dwc3-1111  ( 1111) [000] .... 70.000935: irq_handler_exit: irq=504 ret=handled
    ....

Cc: stable <stable@kernel.org>
Suggested-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Fixes: d325a1de ("usb: dwc3: gadget: Prevent losing events in event cache")
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/20250216223003.3568039-1-badhri@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>