netdev - Re: r8151: check disconnect status after long sleep

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Message-ID: <20200224230240.GA9642@google.com>
Date:   Mon, 24 Feb 2020 15:02:40 -0800
From:   Prashant Malani <pmalani@...omium.org>
To:     You-Sheng Yang <vicamo.yang@...onical.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Hayes Wang <hayeswang@...ltek.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Grant Grundler <grundler@...omium.org>,
        You-Sheng Yang <vicamo@...il.com>, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: r8151: check disconnect status after long sleep

nit: The commit message title tag should be "r8152", instead of "r8151".

On Mon, Feb 24, 2020 at 03:15:41PM +0800, You-Sheng Yang wrote:
> Dell USB Type C docking WD19/WD19DC attaches additional peripherals as:
> 
>   /: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/6p, 5000M
>       |__ Port 1: Dev 11, If 0, Class=Hub, Driver=hub/4p, 5000M
>           |__ Port 3: Dev 12, If 0, Class=Hub, Driver=hub/4p, 5000M
>           |__ Port 4: Dev 13, If 0, Class=Vendor Specific Class,
>               Driver=r8152, 5000M
> 
> where usb 2-1-3 is a hub connecting all USB Type-A/C ports on the dock.
> 
> When hotplugging such dock with additional usb devices already attached on
> it, the probing process may reset usb 2.1 port, therefore r8152 ethernet
> device is also reset. However, during r8152 device init there are several
> for-loops that, when it's unable to retrieve hardware registers due to
> being discconected from USB, may take up to 14 seconds each in practice,
> and that has to be completed before USB may re-enumerate devices on the
> bus. As a result, devices attached to the dock will only be available
> after nearly 1 minute after the dock was plugged in:
> 
>   [ 216.388290] [250] r8152 2-1.4:1.0: usb_probe_interface
>   [ 216.388292] [250] r8152 2-1.4:1.0: usb_probe_interface - got id
>   [ 258.830410] r8152 2-1.4:1.0 (unnamed net_device) (uninitialized): PHY not ready
>   [ 258.830460] r8152 2-1.4:1.0 (unnamed net_device) (uninitialized): Invalid header when reading pass-thru MAC addr
>   [ 258.830464] r8152 2-1.4:1.0 (unnamed net_device) (uninitialized): Get ether addr fail
> 
> This can be reproduced on all kernel versions up to latest v5.6-rc2, but
> after v5.5-rc7 the reproduce rate is dramatically lower to 1/30 or so
> while it was around 1/2.
> 
> The time consuming for-loops are at:
> https://elixir.bootlin.com/linux/v5.5/source/drivers/net/usb/r8152.c#L3206
> https://elixir.bootlin.com/linux/v5.5/source/drivers/net/usb/r8152.c#L5400
> https://elixir.bootlin.com/linux/v5.5/source/drivers/net/usb/r8152.c#L5537
> 
> Signed-off-by: You-Sheng Yang <vicamo.yang@...onical.com>
> ---
>  drivers/net/usb/r8152.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index 78ddbaf6401b..95b19ce96513 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -3221,6 +3221,8 @@ static u16 r8153_phy_status(struct r8152 *tp, u16 desired)
>  		}
>  
>  		msleep(20);
> +		if (test_bit(RTL8152_UNPLUG, &tp->flags))
> +			break;
>  	}
>  
>  	return data;
> @@ -5402,7 +5404,10 @@ static void r8153_init(struct r8152 *tp)
>  		if (ocp_read_word(tp, MCU_TYPE_PLA, PLA_BOOT_CTRL) &
>  		    AUTOLOAD_DONE)
>  			break;
> +
>  		msleep(20);
> +		if (test_bit(RTL8152_UNPLUG, &tp->flags))
> +			break;
>  	}
>  
>  	data = r8153_phy_status(tp, 0);
> @@ -5539,7 +5544,10 @@ static void r8153b_init(struct r8152 *tp)
>  		if (ocp_read_word(tp, MCU_TYPE_PLA, PLA_BOOT_CTRL) &
>  		    AUTOLOAD_DONE)
>  			break;
> +
>  		msleep(20);
> +		if (test_bit(RTL8152_UNPLUG, &tp->flags))
> +			break;
>  	}
>  
>  	data = r8153_phy_status(tp, 0);
> -- 
> 2.25.0
>