linux-kernel - Re: [PATCH 1/2] usb: chipidea: Reduce ULPI PHY reset pulse to datasheet spec of 1us

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Message-ID: <20150630020607.GA7586@shlinux2>
Date:	Tue, 30 Jun 2015 10:06:08 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	Mike Looijmans <mike.looijmans@...ic.nl>
CC:	<lars@...afoo.de>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] usb: chipidea: Reduce ULPI PHY reset pulse to
 datasheet spec of 1us

On Fri, Jun 26, 2015 at 03:47:03PM +0200, Mike Looijmans wrote:
> The datasheet for the 334x PHY mentions that a reset can be performed:
> "... by bringing the pin low for a minimum of 1 microsecond and
> then high."
> A delay of 5ms to implement that seems overly long, so reduce it to
> just 1us.
> As for the delay after reset, the datasheet only mentioned that the
> chip will assert the DIR output. 1ms seems like a safe time to wait
> for that to happen, so no change there.
> 
> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
> ---
>  drivers/usb/chipidea/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/chipidea/core.c b/drivers/usb/chipidea/core.c
> index e970863..c865abe 100644
> --- a/drivers/usb/chipidea/core.c
> +++ b/drivers/usb/chipidea/core.c
> @@ -664,7 +664,7 @@ static int ci_hdrc_create_ulpi_phy(struct device *dev, struct ci_hdrc *ci)
>  			dev_err(dev, "Failed to request ULPI reset gpio: %d\n", ret);
>  			return ret;
>  		}
> -		msleep(5);
> +		udelay(1);
>  		gpio_set_value_cansleep(reset_gpio, 1);
>  		msleep(1);
>  	}
> -- 
> 1.9.1
> 

We have no such function at mainline code.

-- 

Best Regards,
Peter Chen
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