From mboxrd@z Thu Jan 1 00:00:00 1970 From: hzpeterchen@gmail.com (Peter Chen) Date: Thu, 16 Feb 2017 09:23:07 +0800 Subject: [PATCH v13 06/12] usb: xhci: use bus->sysdev for DMA configuration In-Reply-To: <87mvdnoenw.fsf@linux.intel.com> References: <1486776443-2280-7-git-send-email-peter.chen@nxp.com> <20170215013514.GA6579@b29397-desktop> <20170215085127.GA26227@b29397-desktop> <2a3d2d65-e531-aaca-d5a1-a71f818cec61@ti.com> <87mvdnoenw.fsf@linux.intel.com> Message-ID: <20170216012307.GA30290@b29397-desktop> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Feb 15, 2017 at 01:51:31PM +0200, Felipe Balbi wrote: > > Hi, > > Roger Quadros writes: > >>>>>>>> Why are we using sysdev to read DT property? We should be using the > >>>>>>>> XHCI device (&pdev->dev) here, no? > >>>>>>> > >>>>>>> If I remember correctly, this is one of the cases where pdev does not > >>>>>>> have a device node attached to it because it was created by the driver > >>>>>>> of the parent device on the fly in case of dwc3. When you have a pure xhci > >>>>>>> device in DT, the two pointers are the same. > >>>>>> > >>>>>> From drivers/usb/dwc3/host.c > >>>>>> > >>>>>>> if (dwc->usb3_lpm_capable) { > >>>>>>> props[0].name = "usb3-lpm-capable"; > >>>>>>> ret = platform_device_add_properties(xhci, props); > >>>>>>> if (ret) { > >>>>>>> dev_err(dwc->dev, "failed to add properties to xHCI\n"); > >>>>>>> goto err1; > >>>>>>> } > >>>>>>> } > >>>>>> > >>>>>> So it is setting the usb3-lpm-capable property into the xhci platform device > >>>>>> and we should be reading the property from there. > >>>> > >>>> Why dwc3 needs another "snps,usb3_lpm_capable"? Why not using > >>>> "usb3-lpm-capable" at firmware directly? > >>> > >>> dwc3 is not setting "snps,usb3_lpm_capable" but "usb3-lpm-capable" for the > >>> xhci platform device. > >>> > >>> What did you mean by firmware? Did you mean something like BIOS? > >>> At least TI platforms don't use any firmware like BIOS. So dwc3 driver > >>> needs to create a platform device for xhci on the fly and set the DT properties. > >>> > >> > >> By readying code, the dwc3 calls dwc3_get_properties to set > >> dwc->usb3_lpm_capable, and at dwc3/host.c, it sets property > >> "usb3-lpm-capable" according to this flag, why not let common > >> code xhci-plat.c to get this property from sysdev which is DT > >> nodes for dwc3? > >> > > > > Felipe, any comments? > > Won't work. We have quirk flags which are based on DWC3's revision which > is not accessible by xhci-plat. Also, we can't call > device_add_property() because it's not really *adding*. It's *setting*, > meaning that we would loose all other properties. > Sorry, I am not clear by reading the code, here we just discuss "usb3-lpm-capable" property from DT or other firmwares. -- Best Regards, Peter Chen