Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756358AbcJUAm5 (ORCPT ); Thu, 20 Oct 2016 20:42:57 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:35719 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755976AbcJUAmx (ORCPT ); Thu, 20 Oct 2016 20:42:53 -0400 Subject: Re: [RFC][PATCH 2/2] usb: dwc2: Add a quirk to allow speed negotiation for Hisilicon Hi6220 To: John Youn , John Stultz , lkml References: <1476401397-26497-1-git-send-email-john.stultz@linaro.org> <1476401397-26497-3-git-send-email-john.stultz@linaro.org> <2c58c084-704e-3cac-70a1-c8b31661b3d6@synopsys.com> <3d9a84ee-f17e-e93a-17a2-d2dac3be9e58@huawei.com> <3ab39230-0d6b-509e-e26f-b7f7d8549369@synopsys.com> CC: , Wei Xu , Guodong Xu , Amit Pundir , Rob Herring , Mark Rutland , Douglas Anderson , Greg Kroah-Hartman , "linux-usb@vger.kernel.org" From: Chen Yu Message-ID: <07e16fd3-7e27-3346-4e25-b2baa6c15c46@huawei.com> Date: Fri, 21 Oct 2016 08:39:05 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <3ab39230-0d6b-509e-e26f-b7f7d8549369@synopsys.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.142.63.192] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5036 Lines: 143 On 2016/10/19 6:21, John Youn wrote: > On 10/16/2016 7:42 PM, Chen Yu wrote: >> >> >> On 2016/10/15 3:37, John Youn wrote: >>> On 10/13/2016 4:36 PM, John Stultz wrote: >>>> From: Chen Yu >>>> >>>> The Hi6220's usb controller is limited in that it does not >>>> automatically autonegotiate the usb speed. Thus it requires a >>>> quirk so that we can manually negotiate the best usb speed for >>>> the attached device. >>> >>> Hi, >>> >>> Could you expand more on this by explaining what exactly is the >>> limitation and the workaround? >>> >> >> The USB host limitation of Hisilicon Hi6220 is full-speed and low-speed >> devices can not be enumerated when gets plugged behind a hub. >> >>> [snip] >>> >>>> +/* >>>> + * HPRT0_SPD_HIGH_SPEED: high speed >>>> + * HPRT0_SPD_FULL_SPEED: full speed >>>> + */ >>>> +static void dwc2_change_bus_speed(struct usb_hcd *hcd, int speed) >>>> +{ >>>> + struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd); >>>> + >>>> + if (hsotg->core_params->speed == speed) >>>> + return; >>>> + >>>> + hsotg->core_params->speed = speed; >>>> + queue_work(hsotg->wq_otg, &hsotg->wf_otg); >>>> +} >>>> + >>>> +static int dwc2_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev) >>>> +{ >>>> + struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd); >>>> + >>>> + if (!hsotg->change_speed_quirk) >>>> + return 1; >>>> + >>>> + hsotg->device_count++; >>> >>> Why do you need to track the device count? >>> >>>> + dev_info(hsotg->dev, "Device count is %u after alloc dev\n", >>>> + hsotg->device_count); >>>> + >>>> + return 1; >>>> +} >>>> + >>>> +static void dwc2_free_dev(struct usb_hcd *hcd, struct usb_device *udev) >>>> +{ >>>> + struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd); >>>> + >>>> + if (!hsotg->change_speed_quirk) >>>> + return; >>>> + >>>> + if (hsotg->device_count) >>>> + hsotg->device_count--; >>>> + >>>> + dev_info(hsotg->dev, "Device count is %u after free dev\n", >>>> + hsotg->device_count); >>>> + >>>> + if (hsotg->device_count == 1 && udev->parent && >>>> + udev->parent->speed > USB_SPEED_UNKNOWN && >>>> + udev->parent->speed < USB_SPEED_HIGH) { >>>> + dev_info(hsotg->dev, "Set speed to default high-speed\n"); >>>> + dwc2_change_bus_speed(hcd, HPRT0_SPD_HIGH_SPEED); >>>> + } >>>> +} >>>> + >>>> +static int dwc2_reset_device(struct usb_hcd *hcd, struct usb_device *udev) >>>> +{ >>>> + struct dwc2_hsotg *hsotg = dwc2_hcd_to_hsotg(hcd); >>>> + >>>> + if (!hsotg->change_speed_quirk) >>>> + return 0; >>>> + >>>> + if (udev->speed == USB_SPEED_HIGH) { >>>> + dev_info(hsotg->dev, "Set speed to high-speed\n"); >>>> + dwc2_change_bus_speed(hcd, HPRT0_SPD_HIGH_SPEED); >>>> + } else if (udev->speed == USB_SPEED_FULL >>>> + || udev->speed == USB_SPEED_LOW) { >>>> + dev_info(hsotg->dev, "Set speed to full-speed\n"); >>>> + dwc2_change_bus_speed(hcd, HPRT0_SPD_FULL_SPEED); >>>> + } >>> >>> It seems you are reinitializing the core every time a device is reset >>> and the udev->speed does not match the core_param speed. But how is >>> the udev->speed being set correctly if the hw cannot negotiate the >>> speed in the first place? >>> >> >> The hardware can negotiate the speed, but communication with a full-speed or >> low-speed device behind a hub is the problem. >> >>> Also should it be for every device? What about if a device gets >>> plugged in behind a hub? I don't think you want to execute this code >>> in that case. >>> >>> This should only affect devices plugged into the root hub, correct? >>> And the hsotg controller only has one root hub port. It seems things >>> could be simplified a bit. >>> >> >> The patch is initially written for Hikey Hi6220 board, and there is a >> hub always connected to root hub, so the patch sets the configuration to >> HPRT0_SPD_HIGH_SPEED when there is only one device(the hub). > > Ok, I see. > >> >> Thanks for your suggestions, the patch needs modified in these aspect: >> 1. Change the speed setting only when the device is behind a hub in dwc2_reset_device. > > I still think you will have issues with multiple devices. Since you > have a built-in hub after root hub, it will always be behind the > hub. So whenver you need to change speeds, it will always reset every > device in the tree. Have you tested with multiple devices and also > multiple levels of hubs? > Yes, a full-speed device or low-speed device being plugged in will reset other devices if current speed setting is not full-speed. I have tested with multiple devices and also two levels of high-speed hubs, the patch was working well for enumerating full-speed device and low-speed device. Also it changed the speed to high when there was only one hub connected to root hub. >> 2. Change the speed to HPRT0_SPD_HIGH_SPEED only when the last device is a hub. >> >> What do you think about the fix? Any suggestions will be appreciate! > > I'm not sure if any fix can work for all cases. Has this problem > always been there? Yes, the problem is always there because Hi6220 can not support "Split Transaction".