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Message-ID: <5550BA31.10901@ti.com> Date: Mon, 11 May 2015 17:18:25 +0300 From: Roger Quadros <rogerq@...com> To: Mathias Nyman <mathias.nyman@...ux.intel.com>, <mathias.nyman@...el.com>, Alan Stern <stern@...land.harvard.edu> CC: <gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 1/5] usb: xhci: cleanup xhci_hcd allocation Hi Mathias, On 13/04/15 15:48, Mathias Nyman wrote: > Hi > > On 09.04.2015 12:22, Roger Quadros wrote: >> Hi, >> >> On 07/04/15 17:23, Mathias Nyman wrote: >>> Hi >>> >>> On 02.04.2015 15:23, Roger Quadros wrote: >>>> HCD core allocates memory for HCD private data in >>>> usb_create_[shared_]hcd() so make use of that >>>> mechanism to allocate the struct xhci_hcd. >>>> >>>> Introduce struct xhci_driver_overrides to provide >>>> the size of HCD private data and hc_driver operation >>>> overrides. As of now we only need to override the >>>> reset and start methods. >>>> >>>> Signed-off-by: Roger Quadros <rogerq@...com> >>> >>> I'm not sure I fully understand the what's going on, or what the >>> intention of this patch is. >> >> The main intention is to have both primary and shared HCDs allocated >> before calling usb_add_hcd() for the primary hcd. >> This is so that at the first usb_add_hcd() the OTG core knows the HCD topology >> (i.e. whether it uses a shared HCD or not). >> >> From the OTG perspective we have to prevent the actual usb_add_hcd() till the >> OTG state machine says so. >> This means that xhci_gen_setup() won't be necessarily called immediately and >> so we need to allocate for xhci somewhere else. > > Ok, thanks for explaining. I now understand the reason behind this. > >> >>> >>> So currently xhci driver manages the allocation and freeing of >>> the xhci_hcd structure. We store a pointer to the xhci_hcd structure in >>> the content of both the primary and shared usb_hcds structures hcd_priv >>> field. >>> >>> With this patch xhci would be part of the usb_hcd structure, >>> starting at hcd_priv[0]. (Like EHCI I think) It allocates enough space to include >>> the xhci_hcd in both the primary and shared usb_hcd, but always only use the one >>> in the primary hcd. >> >> precisely. >> >>> I'm not sure what to do with the space allocated for the shared hcd's >>> hcd_priv field. >> >> we just ignore the space allocated for the shared hcd. > > Ok, not a big loss. > >> >>> >>> This also means that xhci goes away together with the primary hcd. It's possible >>> this has some impact as the xhci driver expects xhci to always exists. >> >> Can you please point out where this impact is. >> >> I've been testing add/remove HCD extensively and didn't observe any issues after applying >> these 5 patches. Well there is one issue that comes up but it has nothing to do with xhci >> not being allocated. It has more to do with command being queued after the HCD has gone away >> and so getting stuck forever without timing out. > > I went through the codepaths and you're right, should work fine. My concern wasn't valid. > This patchset doesn't even touch the order how primary and shared HCDs are created and added > in the PCI case, only for the platform device case. > > I'll try it out and send forward once rc1 is out. did you get a chance to try this series? cheers, -roger -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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