linux-kernel - Re: [usb-next PATCH] usb: xhci: skip phys initialization of shared hcd

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Date:   Wed, 21 Mar 2018 19:50:20 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Roger Quadros <rogerq@...com>
CC:     Mathias Nyman <mathias.nyman@...el.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-usb@...r.kernel.org>, <linux-mediatek@...ts.infradead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [usb-next PATCH] usb: xhci: skip phys initialization of shared
 hcd

Hi Roger,

On Wed, 2018-03-21 at 11:05 +0200, Roger Quadros wrote:
> Hi Chunfeng,
> 
> On 21/03/18 08:12, Chunfeng Yun wrote:
> > The phys has already been initialized when add primary hcd,
> > including usb2 phys and usb3 phys also if exist, so needn't
> > re-parse "phys" property again.
> > 
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > ---
> >  drivers/usb/host/xhci-mtk.c  | 1 +
> >  drivers/usb/host/xhci-plat.c | 1 +
> >  2 files changed, 2 insertions(+)
> > 
> > diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
> > index 7334da9..6bb23fb 100644
> > --- a/drivers/usb/host/xhci-mtk.c
> > +++ b/drivers/usb/host/xhci-mtk.c
> > @@ -554,6 +554,7 @@ static int xhci_mtk_probe(struct platform_device *pdev)
> >  	if (HCC_MAX_PSA(xhci->hcc_params) >= 4)
> >  		xhci->shared_hcd->can_do_streams = 1;
> >  
> > +	xhci->shared_hcd->skip_phy_initialization = 1;
> >  	ret = usb_add_hcd(xhci->shared_hcd, irq, IRQF_SHARED);
> >  	if (ret)
> >  		goto dealloc_usb2_hcd;
> > diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> > index 6700e5e..65a4294 100644
> > --- a/drivers/usb/host/xhci-plat.c
> > +++ b/drivers/usb/host/xhci-plat.c
> > @@ -294,6 +294,7 @@ static int xhci_plat_probe(struct platform_device *pdev)
> >  	if (HCC_MAX_PSA(xhci->hcc_params) >= 4)
> >  		xhci->shared_hcd->can_do_streams = 1;
> >  
> > +	xhci->shared_hcd->skip_phy_initialization = 1;
> 
> I think this is unnecessary.
> There aren't separate PHYs for the primary and shared HCDs right?
Yes, the primary and shared HCDs will get the same PHYs provided by
"phys" property.

> 
> Also how can you be sure that phy_init() has been done for all platform HCD users?
Here I assume that "phys" and "usb-phy" properties are not used at the
same time. There are two cases:
1. Using "usb-phy": no "phys" to be got by shared HCD.
2. Using "phys": the primary HCD will get those phys, so shared HCD can
skip them.

> 
> >  	ret = usb_add_hcd(xhci->shared_hcd, irq, IRQF_SHARED);
> >  	if (ret)
> >  		goto dealloc_usb2_hcd;
> > 
>