Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] r8169: inform about CLKRUN protocol issue when behind a
 CardBus bridge
To:     David Miller <davem@davemloft.net>
Cc:     nic_swsd@realtek.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <fcf6a23a-4721-5912-281e-488eb6a736c6@maciej.szmigiero.name>
 <20180909.080907.992434701890231030.davem@davemloft.net>
From:   "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Openpgp: preference=signencrypt
Autocrypt: addr=mail@maciej.szmigiero.name; prefer-encrypt=mutual; keydata=
 xsFNBFpGusUBEADXUMM2t7y9sHhI79+2QUnDdpauIBjZDukPZArwD+sDlx5P+jxaZ13XjUQc
 6oJdk+jpvKiyzlbKqlDtw/Y2Ob24tg1g/zvkHn8AVUwX+ZWWewSZ0vcwp7u/LvA+w2nJbIL1
 N0/QUUdmxfkWTHhNqgkNX5hEmYqhwUPozFR0zblfD/6+XFR7VM9yT0fZPLqYLNOmGfqAXlxY
 m8nWmi+lxkd/PYqQQwOq6GQwxjRFEvSc09m/YPYo9hxh7a6s8hAP88YOf2PD8oBB1r5E7KGb
 Fv10Qss4CU/3zaiyRTExWwOJnTQdzSbtnM3S8/ZO/sL0FY/b4VLtlZzERAraxHdnPn8GgxYk
 oPtAqoyf52RkCabL9dsXPWYQjkwG8WEUPScHDy8Uoo6imQujshG23A99iPuXcWc/5ld9mIo/
 Ee7kN50MOXwS4vCJSv0cMkVhh77CmGUv5++E/rPcbXPLTPeRVy6SHgdDhIj7elmx2Lgo0cyh
 uyxyBKSuzPvb61nh5EKAGL7kPqflNw7LJkInzHqKHDNu57rVuCHEx4yxcKNB4pdE2SgyPxs9
 9W7Cz0q2Hd7Yu8GOXvMfQfrBiEV4q4PzidUtV6sLqVq0RMK7LEi0RiZpthwxz0IUFwRw2KS/
 9Kgs9LmOXYimodrV0pMxpVqcyTepmDSoWzyXNP2NL1+GuQtaTQARAQABzTBNYWNpZWogUy4g
 U3ptaWdpZXJvIDxtYWlsQG1hY2llai5zem1pZ2llcm8ubmFtZT7CwZQEEwEIAD4WIQRyeg1N
 257Z9gOb7O+Ef143kM4JdwUCWka6xQIbAwUJA8JnAAULCQgHAgYVCgkICwIEFgIDAQIeAQIX
 gAAKCRCEf143kM4Jdx4+EACwi1bXraGxNwgFj+KI8T0Xar3fYdaOF7bb7cAHllBCPQkutjnx
 8SkYxqGvSNbBhGtpL1TqAYLB1Jr+ElB8qWEV6bJrffbRmsiBPORAxMfu8FF+kVqCYZs3nbku
 XNzmzp6R/eii40S+XySiscmpsrVQvz7I+xIIYdC0OTUu0Vl3IHf718GBYSD+TodCazEdN96k
 p9uD9kWNCU1vnL7FzhqClhPYLjPCkotrWM4gBNDbRiEHv1zMXb0/jVIR/wcDIUv6SLhzDIQn
 Lhre8LyKwid+WQxq7ZF0H+0VnPf5q56990cEBeB4xSyI+tr47uNP2K1kmW1FPd5q6XlIlvh2
 WxsG6RNphbo8lIE6sd7NWSY3wXu4/R1AGdn2mnXKMp2O9039ewY6IhoeodCKN39ZR9LNld2w
 Dp0MU39LukPZKkVtbMEOEi0R1LXQAY0TQO//0IlAehfbkkYv6IAuNDd/exnj59GtwRfsXaVR
 Nw7XR/8bCvwU4svyRqI4luSuEiXvM9rwDAXbRKmu+Pk5h+1AOV+KjKPWCkBEHaASOxuApouQ
 aPZw6HDJ3fdFmN+m+vNcRPzST30QxGrXlS5GgY6CJ10W9gt/IJrFGoGxGxYjj4WzO97Rg6Mq
 WMa7wMPPNcnX5Nc/b8HW67Jhs3trj0szq6FKhqBsACktOU4g/ksV8eEtnM7AzQRaRrwiAQwA
 xnVmJqeP9VUTISps+WbyYFYlMFfIurl7tzK74bc67KUBp+PHuDP9p4ZcJUGC3UZJP85/GlUV
 dE1NairYWEJQUB7bpogTuzMI825QXIB9z842HwWfP2RW5eDtJMeujzJeFaUpmeTG9snzaYxY
 N3r0TDKj5dZwSIThIMQpsmhH2zylkT0jH7kBPxb8IkCQ1c6wgKITwoHFjTIO0B75U7bBNSDp
 XUaUDvd6T3xd1Fz57ujAvKHrZfWtaNSGwLmUYQAcFvrKDGPB5Z3ggkiTtkmW3OCQbnIxGJJw
 /+HefYhB5/kCcpKUQ2RYcYgCZ0/WcES1xU5dnNe4i0a5gsOFSOYCpNCfTHttVxKxZZTQ/rxj
 XwTuToXmTI4Nehn96t25DHZ0t9L9UEJ0yxH2y8Av4rtf75K2yAXFZa8dHnQgCkyjA/gs0ujG
 wD+Gs7dYQxP4i+rLhwBWD3mawJxLxY0vGwkG7k7npqanlsWlATHpOdqBMUiAR22hs02FikAo
 iXNgWTy7ABEBAAHCwXwEGAEIACYWIQRyeg1N257Z9gOb7O+Ef143kM4JdwUCWka8IgIbDAUJ
 A8JnAAAKCRCEf143kM4Jd9nXD/9jstJU6L1MLyr/ydKOnY48pSlZYgII9rSnFyLUHzNcW2c/
 qw9LPMlDcK13tiVRQgKT4W+RvsET/tZCQcap2OF3Z6vd1naTur7oJvgvVM5lVhUia2O60kEZ
 XNlMLFwLSmGXhaAXNBySpzN2xStSLCtbK58r7Vf9QS0mR0PGU2v68Cb8fFWcYu2Yzn3RXf0Y
 dIVWvaQG9whxZq5MdJm5dknfTcCG+MtmbP/DnpQpjAlgVmDgMgYTBW1W9etU36YW0pTqEYuv
 6cmRgSAKEDaYHhFLTR1+lLJkp5fFo3Sjm7XqmXzfSv9JGJGMKzoFOMBoLYv+VFnMoLX5UJAs
 0JyFqFY2YxGyLd4J103NI/ocqQeU0TVvOZGVkENPSxIESnbxPghsEC0MWEbGsvqA8FwvU7Xf
 GhZPYzTRf7CndDnezEA69EhwpZXKs4CvxbXo5PDTv0OWzVaAWqq8s8aTMJWWAhvobFozJ63z
 afYHkuEjMo0Xps3o3uvKg7coooH521nNsv4ci+KeBq3mgMCRAy0g/Ef+Ql7mt900RCBHu4tk
 tOhPc3J1ep/e2WAJ4ngUqJhilzyCJnzVJ4cT79VK/uPtlfUCZdUz+jTC88TmP1p5wlucS31k
 Thy/CV4cqDFB8yzEujTSiRzd7neG3sH0vcxBd69uvSxLZPLGID840k0v5sftPA==
Message-ID: <0a5f601c-88cc-4d5e-94f1-f38dbd093fc0@maciej.szmigiero.name>
Date:   Mon, 10 Sep 2018 00:01:53 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.0
MIME-Version: 1.0
In-Reply-To: <20180909.080907.992434701890231030.davem@davemloft.net>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 09.09.2018 17:09, David Miller wrote:
> From: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
> Date: Thu, 6 Sep 2018 18:10:53 +0200
> 
>> It turns out that at least some r8169 CardBus cards don't operate correctly
>> when CLKRUN protocol is enabled - the symptoms are recurring timeouts
>> during PHY reads / writes and a very high packet drop rate.
>> This is true of at least RTL8169sc/8110sc (XID 18000000) chip in
>> Sunrich C-160 CardBus NIC.
>>
>> Such behavior was observed on two separate laptops, the first one has
>> TI PCIxx12 CardBus bridge, while the second one has Ricoh RL5c476II.
>>
>> Setting CLKRUN_En bit in CONFIG 3 register via an EEPROM write didn't
>> improve things in either case (this is probably why it wasn't set by the
>> card manufacturer).
>> The only way to fix the issue was to disable the CLKRUN protocol either
>> in the CardBus bridge (only possible in the TI one) or in the southbridge.
>>
>> Since the problem takes some time to debug let's warn people that have
>> the suspect configuration (Conventional PCI r8169 NIC behind a CardBus
>> bridge) so they know what they can do if they encounter it.
>>
>> Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
> 
> I don't know about this.
> 
> Barking at the user in the kernel log about an obscure knob (which btw
> doesn't exist for all cardbus bridges without other patches you are
> posting elsewhere) is rarely effective.
> 
> We should just disable clkrun automatically we know it causes problems.

Unfortunately, as you wrote above, this workaround is only available on
TI CardBus bridges (and I hope will be available for two Ricoh ones soon,
too), while for other CardBus bridges it is either not implemented or
not available at all.
So we can't reliably just turn it on automatically when needed.

BTW, it seems that my RTL8169 card isn't the only model affected.
In fact, the original CLKRUN protocol disabling workaround on TI bridges
was implemented in 2005 because somebody's RTL8139 also had this
problem: https://lkml.org/lkml/2005/2/5/129

The main reason I wanted to add this warning is to save people time
debugging this issue, as it is rather unobvious.
But if this solution is unacceptable then I hope at least this
description will pop out in search results when searching for some
related keywords.

Thanks,
Maciej