From: Felipe Balbi <balbi@kernel•org>
To: rentao.bupt@gmail•com,
Greg Kroah-Hartman <gregkh@linuxfoundation•org>,
Joel Stanley <joel@jms•id.au>, Andrew Jeffery <andrew@aj•id.au>,
Benjamin Herrenschmidt <benh@kernel•crashing.org>,
Chunfeng Yun <chunfeng.yun@mediatek•com>,
Stephen Boyd <swboyd@chromium•org>,
linux-usb@vger•kernel.org, linux-arm-kernel@lists•infradead.org,
linux-aspeed@lists•ozlabs.org, linux-kernel@vger•kernel.org,
openbmc@lists•ozlabs.org, taoren@fb•com
Cc: Tao Ren <rentao.bupt@gmail•com>
Subject: Re: [PATCH] usb: gadget: aspeed: fixup vhub port irq handling
Date: Mon, 17 Aug 2020 16:49:32 +0300 [thread overview]
Message-ID: <875z9hz8k3.fsf@kernel.org> (raw)
In-Reply-To: <20200528011154.30355-1-rentao.bupt@gmail.com>
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Hi,
rentao.bupt@gmail•com writes:
> From: Tao Ren <rentao.bupt@gmail•com>
>
> This is a follow-on patch for commit a23be4ed8f48 ("usb: gadget: aspeed:
> improve vhub port irq handling"): for_each_set_bit() is replaced with
> simple for() loop because for() loop runs faster on ASPEED BMC.
>
> Signed-off-by: Tao Ren <rentao.bupt@gmail•com>
> ---
> drivers/usb/gadget/udc/aspeed-vhub/core.c | 10 +++-------
> drivers/usb/gadget/udc/aspeed-vhub/vhub.h | 3 +++
> 2 files changed, 6 insertions(+), 7 deletions(-)
>
> 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.
--
balbi
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next prev parent reply other threads:[~2020-08-17 13:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-28 1:11 [PATCH] usb: gadget: aspeed: fixup vhub port irq handling rentao.bupt
2020-05-28 1:20 ` Tao Ren
2020-08-17 13:49 ` Felipe Balbi [this message]
2020-08-17 22:56 ` Tao Ren
2020-08-31 9:54 ` Felipe Balbi
2020-08-31 9:54 ` Felipe Balbi
2020-08-31 23:26 ` Tao Ren
2020-08-31 9:56 ` Felipe Balbi
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