lkml.org 
[lkml]   [2015]   [Jul]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH 1/2] usb: chipidea: Reduce ULPI PHY reset pulse to datasheet spec of 1us
Date
From: Peter Chen
> Sent: 30 June 2015 03:06
> 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@topic.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);

If the spec says 1us I'd delay for longer just to make sure.
And add a comment saying that the reset needs to be 1us long.

David



\
 
 \ /
  Last update: 2015-07-02 12:01    [W:0.064 / U:0.452 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site