Re: [PATCH v2 3/3] usb: misc: onboard_usb_hub: Add TI USB8041 hub support

[Matthias Kaehlcke <mka@chromium.org>]

On Wed, Jul 20, 2022 at 09:18:50AM +0200, Alexander Stein wrote:
> Am Freitag, 15. Juli 2022, 21:50:41 CEST schrieb Matthias Kaehlcke:
> > On Fri, Jul 15, 2022 at 09:33:00AM +0200, Alexander Stein wrote:
> > > This is a 4-port 3.0 USB hub.
> > > 
> > > Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
> > > ---
> > > Changes in v2:
> > > * Add devtype data containing waiting times
> > > 
> > >  drivers/usb/misc/onboard_usb_hub.c | 3 +++
> > >  drivers/usb/misc/onboard_usb_hub.h | 7 +++++++
> > >  2 files changed, 10 insertions(+)
> > > 
> > > diff --git a/drivers/usb/misc/onboard_usb_hub.c
> > > b/drivers/usb/misc/onboard_usb_hub.c index 1dd7f4767def..319b4b1748fb
> > > 100644
> > > --- a/drivers/usb/misc/onboard_usb_hub.c
> > > +++ b/drivers/usb/misc/onboard_usb_hub.c
> > > @@ -339,6 +339,7 @@ static struct platform_driver onboard_hub_driver = {
> > > 
> > >  /************************** USB driver **************************/
> > >  
> > >  #define VENDOR_ID_REALTEK	0x0bda
> > > 
> > > +#define VENDOR_ID_TI		0x0451
> > > 
> > >  /*
> > >  
> > >   * Returns the onboard_hub platform device that is associated with the
> > >   USB
> > > 
> > > @@ -416,6 +417,8 @@ static const struct usb_device_id
> > > onboard_hub_id_table[] = {> 
> > >  	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x5411) }, /* RTS5411 USB 2.1 */
> > >  	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x0414) }, /* RTS5414 USB 3.2 */
> > >  	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x5414) }, /* RTS5414 USB 2.1 */
> > > 
> > > +	{ USB_DEVICE(VENDOR_ID_TI, 0x8140) }, /* TI USB8041 3.0 */
> > > +	{ USB_DEVICE(VENDOR_ID_TI, 0x8142) }, /* TI USB8041 2.0 */
> > > 
> > >  	{}
> > >  
> > >  };
> > >  MODULE_DEVICE_TABLE(usb, onboard_hub_id_table);
> > > 
> > > diff --git a/drivers/usb/misc/onboard_usb_hub.h
> > > b/drivers/usb/misc/onboard_usb_hub.h index 7e743f4c8aaa..fcb6a9024bbd
> > > 100644
> > > --- a/drivers/usb/misc/onboard_usb_hub.h
> > > +++ b/drivers/usb/misc/onboard_usb_hub.h
> > > @@ -11,7 +11,14 @@ struct onboard_hub_devtype_data {
> > > 
> > >  	unsigned long reset_duration;		/* reset pulse width in 
> us */
> > >  
> > >  };
> > > 
> > > +static const struct onboard_hub_devtype_data ti_tusb8041_data = {
> > > +	.power_stable_time = 3000,
> > > +	.reset_duration = 3000,
> > 
> > Aren't these two values actually the same thing, i.e. the minimum
> > duration of the reset?
> > 
> > From the data sheet:
> > 
> >   A minimum reset duration of 3 ms is required
> > 
> >   td2: VDD and VDD33 stable before de-assertion of GRSTz (>= 3ms)
> > 
> > My understanding is that td2 is just another expression of the first
> > requirement.
> 
> They may have the same values, but IMHO they are applied differently.
> 'power_stable_time' (or power_stable_us now) applies after supplying power, 
> while 'reset_duration' (or reset_us now) applies when you deassert the reset 
> line. 
> For that reason I would like to keep them separated.

In both cases the datasheet talks about the reset duration of 3 ms in
relation with the power supplies:

  7.6 Timing Requirements, Power-Up

  td2: VDD and VDD33 stable before de-assertion of GRSTz


  8.3.7 Power-Up and Reset

  A minimum reset duration of 3 ms is required. This is defined as the time when
  the power supplies are in the recommended operating range to the de-assertion
  of GRSTz.

At this point I see no good reason for having two different values. If it turns
out later that it is really needed for other hubs another fiels like
'power_stable_us' can still be added.