Re: [PATCH 2/2] usb: usb251xb: make power-up reset delay configurable in device tree

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Apr 26, 2022 at 03:06:34PM +0200, Daniels Umanovskis wrote:
> On 4/26/22 2:46 PM, Greg KH wrote:
> > On Tue, Apr 26, 2022 at 12:34:13PM +0000, Daniels Umanovskis wrote:
> > > According to the datasheet, the hub should be operational 500us after
> > > the reset has been deasserted. Some individual circuits have been
> > > observed not to reset within the specified 500us and require a longer
> > > wait for subsequent configuration to succeed.
> > > 
> > > Signed-off-by: Daniels Umanovskis <du@axentia.se>
> > > ---
> > >   drivers/usb/misc/usb251xb.c | 6 +++++-
> > >   1 file changed, 5 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/usb/misc/usb251xb.c b/drivers/usb/misc/usb251xb.c
> > > index 04c4e3fed094..e287e241ef96 100644
> > > --- a/drivers/usb/misc/usb251xb.c
> > > +++ b/drivers/usb/misc/usb251xb.c
> > > @@ -115,6 +115,7 @@ struct usb251xb {
> > >   	struct regulator *vdd;
> > >   	u8 skip_config;
> > >   	struct gpio_desc *gpio_reset;
> > > +	u32 reset_delay_us;
> > >   	u16 vendor_id;
> > >   	u16 product_id;
> > >   	u16 device_id;
> > > @@ -278,7 +279,7 @@ static void usb251xb_reset(struct usb251xb *hub)
> > >   	gpiod_set_value_cansleep(hub->gpio_reset, 0);
> > >   	/* wait for hub recovery/stabilization */
> > > -	usleep_range(500, 750);	/* >=500us after RESET_N deasserted */
> > > +	fsleep(hub->reset_delay_us);
> > >   	i2c_unlock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT);
> > >   }
> > > @@ -424,6 +425,9 @@ static int usb251xb_get_ofdata(struct usb251xb *hub,
> > >   		return err;
> > >   	}
> > > +	if (of_property_read_u32(np, "reset-delay-us", &hub->reset_delay_us))
> > > +		hub->reset_delay_us = 500;
> > So if this fails the delay is 0?
> of_property_read_u32 can fail with -EINVAL or -ENODATA, then delay is 500,
> unless I'm missing something more obvious.

Ah, no, you are right, sorry, I read this wrong.

greg k-h