Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
From: Felipe Balbi <balbi@kernel.org>
Date: 2020-08-31 09:56:36
Also in:
linux-aspeed, linux-usb, lkml, openbmc
Hi, Tao Ren [off-list ref] writes:
quoted
quoted
diff --git a/drivers/usb/gadget/udc/aspeed-vhub/core.c b/drivers/usb/gadget/udc/aspeed-vhub/core.c index cdf96911e4b1..be7bb64e3594 100644 --- a/drivers/usb/gadget/udc/aspeed-vhub/core.c +++ b/drivers/usb/gadget/udc/aspeed-vhub/core.c@@ -135,13 +135,9 @@ static irqreturn_t ast_vhub_irq(int irq, void *data) /* Handle device interrupts */ if (istat & vhub->port_irq_mask) { - unsigned long bitmap = istat; - int offset = VHUB_IRQ_DEV1_BIT; - int size = VHUB_IRQ_DEV1_BIT + vhub->max_ports; - - for_each_set_bit_from(offset, &bitmap, size) { - i = offset - VHUB_IRQ_DEV1_BIT; - ast_vhub_dev_irq(&vhub->ports[i].dev); + for (i = 0; i < vhub->max_ports; i++) { + if (istat & VHUB_DEV_IRQ(i)) + ast_vhub_dev_irq(&vhub->ports[i].dev);how have you measured your statement above? for_each_set_bit() does exactly what you did. Unless your architecture has an instruction which helps finds the next set bit (like cls on ARM), which, then, makes it much faster.I did some testing and result shows for() loop runs faster than for_each_set_bit() loop. Please refer to details below (discussion with Benjamin in the original patch) and kindly let me know your suggestions.
no strong feelings, just surprised you're already worried about 20~40 cycles of cpu time ;-) patch queued for next merge window -- balbi _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel