linux-kernel - Re: [PATCH v2] usb: dwc3: core: set force_gen1 bit in USB31 devices if max speed is SS

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Message-ID: <20230706223411.mlalnochoabofcmj@synopsys.com>
Date:   Thu, 6 Jul 2023 22:34:16 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
CC:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "quic_ppratap@...cinc.com" <quic_ppratap@...cinc.com>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>,
        "quic_ugoswami@...cinc.com" <quic_ugoswami@...cinc.com>
Subject: Re: [PATCH v2] usb: dwc3: core: set force_gen1 bit in USB31 devices
 if max speed is SS

On Thu, Jul 06, 2023, Krishna Kurapati PSSNV wrote:
> 
> 
> On 5/17/2023 5:41 AM, Thinh Nguyen wrote:
> > On Sun, May 14, 2023, Krishna Kurapati wrote:
> > > Currently for dwc3_usb31 controller, if maximum_speed is limited to
> > > super-speed in DT, then device mode is limited to SS, but host mode
> > > still works in SSP.
> > > 
> > > The documentation for max-speed property is as follows:
> > > 
> > > "Tells USB controllers we want to work up to a certain speed.
> > > Incase  this isn't passed via DT, USB controllers should default to
> > > their maximum HW capability."
> > > 
> > > It doesn't specify that the property is only for device mode.
> > > There are cases where we need to limit the host's maximum speed to
> > > SuperSpeed only. Use this property for host mode to contrain host's
> > > speed to SuperSpeed.
> > > 
> > > Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
> > > ---
> > > Link to v1: https://urldefense.com/v3/__https://lore.kernel.org/all/20230512170107.18821-1-quic_kriskura@quicinc.com/__;!!A4F2R9G_pg!dCg_3WK2oNXNb6d0a_VuyjkeeZJTU1aY4dik6g35XB7mtG7EJeR1uPMfxFja49OfXp7Yhsg1yqjnylCYYEg7YCAhqfAZ0Q$
> > > 
> > > Discussion regarding the same at:
> > > https://urldefense.com/v3/__https://lore.kernel.org/all/e465c69c-3a9d-cbdb-d44e-96b99cfa1a92@quicinc.com/__;!!A4F2R9G_pg!dCg_3WK2oNXNb6d0a_VuyjkeeZJTU1aY4dik6g35XB7mtG7EJeR1uPMfxFja49OfXp7Yhsg1yqjnylCYYEg7YCDRLUrJWg$
> > > 
> > >   drivers/usb/dwc3/core.c | 8 ++++++++
> > >   drivers/usb/dwc3/core.h | 5 +++++
> > >   2 files changed, 13 insertions(+)
> > > 
> > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > > index 278cd1c33841..33bc72595e74 100644
> > > --- a/drivers/usb/dwc3/core.c
> > > +++ b/drivers/usb/dwc3/core.c
> > > @@ -1262,6 +1262,14 @@ static int dwc3_core_init(struct dwc3 *dwc)
> > >   		}
> > >   	}
> > > +	if ((hw_mode != DWC3_GHWPARAMS0_MODE_GADGET) &&
> > > +	    (DWC3_IP_IS(DWC31)) &&
> > > +	    (dwc->maximum_speed == USB_SPEED_SUPER)) {
> > > +		reg = dwc3_readl(dwc->regs, DWC3_LLUCTL);
> > > +		reg |= DWC3_LLUCTL_FORCE_GEN1;
> > > +		dwc3_writel(dwc->regs, DWC3_LLUCTL, reg);
> > > +	}
> > > +
> > 
> > Perhaps this should be done for every usb3 port rather than just the
> > port_0. This patch can go after your multi-port series is added to
> > Greg's branch where you can check for number of usb3 ports.
> > 
> > Thanks,
> > Thinh
> > 
> 
> Hi Thinh,
> 
>   Seems like multiport would take little more time and I need this patch to
> be ported to ACK for fixing customer issue. Would it be possible to take
> this patch as is ? Once multiport is done, I will send another patch to
> include the changes for mutliport as well.
> 

This is not a fix patch. It will not be upstreamed until the next
release even if I Ack it now. Do you think we can get your multi-port
series in for the next release along with this? If not, then we can Ack
this version first (with a note to update for multi-port later).

I think it makes more sense wait and see if we can get your multi-port
series for the next release first. What do you think?

Thanks,
Thinh