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Re: [PATCH V2 2/4] MIPS: Add board support for Loongson1B

To: Giuseppe CAVALLARO <peppe.cavallaro@st.com>
Subject: Re: [PATCH V2 2/4] MIPS: Add board support for Loongson1B
From: Kelvin Cheung <keguang.zhang@gmail.com>
Date: Wed, 26 Oct 2011 15:48:26 +0800
Cc: Wu Zhangjin <wuzhangjin@gmail.com>, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, ralf@linux-mips.org, r0bertz@gentoo.org, netdev@vger.kernel.org
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It's perfect now.
Please add me to CC list when you send the new patch.

Thanks a lot for your help.

2011/10/26, Giuseppe CAVALLARO <peppe.cavallaro@st.com>:
> Hello Kelvin
>
> On 10/26/2011 6:27 AM, Kelvin Cheung wrote:
>> Hi Giuseppe,
>>
>> This patch works well on Loongson1B platform except one thing.
>> The rx checksum offload of normal descriptor is disabled by default.
>> So, I enabled this functon. And one minor tweak is added to your patch.
>> What about your opinion?
>
> Yes, I had not enabled the rx coe. I'm resending your patch (v3) where I
> fixed a problem. Old mac10/100 has no rx csum in HW. So I added an extra
> check.
> Let me consider it the final version. ;-)
>
> Thanks a lot for you effort.
> I'll send it for net-next now.
>
> Regards
> Peppe
>
>>
>> BTW, tx checksum insertion works now.
>>
>> 2011/10/25, Giuseppe CAVALLARO <peppe.cavallaro@st.com>:
>>> On 10/25/2011 9:09 AM, Giuseppe CAVALLARO wrote:
>>>> On 10/25/2011 4:12 AM, Kelvin Cheung wrote:
>>>>> 2011/10/24, Giuseppe CAVALLARO <peppe.cavallaro@st.com>:
>>>>>> On 10/24/2011 4:05 PM, Kelvin Cheung wrote:
>>>>>>> 2011/10/24, Giuseppe CAVALLARO <peppe.cavallaro@st.com>:
>>>>>>>> Hello Kelvin.
>>>>>>>>
>>>>>>>> On 10/24/2011 12:36 PM, Kelvin Cheung wrote:
>>>>>>>>
>>>>>>>> [snip]
>>>>>>>>
>>>>>>>>> According to datasheet of Loongson 1B, the buffer size in RX/TX
>>>>>>>>> descriptor is only 2KB. So the Loongson1B's GMAC could not handle
>>>>>>>>> jumbo frames. And the second buffer is useless in this case. Am I
>>>>>>>>> right? Is there a better way than ifdef CONFIG_MACH_LOONGSON1 to
>>>>>>>>> avoid duplicate code?
>>>>>>>>
>>>>>>>> Sorry for my misunderstanding.
>>>>>>>>
>>>>>>>> I think you have to use the normal descriptor and remove the
>>>>>>>> enh_desc
>>>>>>>> from the platform w/o modifying the driver at all.
>>>>>>>>
>>>>>>>> The driver will be able to select/configure all automatically (also
>>>>>>>> jumbo).
>>>>>>>>
>>>>>>>> Let me know.
>>>>>>>
>>>>>>> That's the problem.
>>>>>>> The bitfield definition of Loongson1B is also different from normal
>>>>>>> descriptor.
>>>>>>
>>>>>> The problem is not in the Loongson1B gmac.
>>>>>
>>>>> I found that the bit checksum_insertion is not existed in normal
>>>>> descriptor.
>>>>>
>>>>>> The normal descriptor fields in the stmmac refer to an old synopsys
>>>>>> databook.
>>>>>
>>>>> Could you send me the new databook of Synopsys GMAC?
>>>>>
>>>>>> New chips have the same structure you have added; so we should fix
>>>>>> this
>>>>>> in the driver w/o breaking the compatibility for old chips.
>>>>>
>>>>> Agree.
>>>>>
>>>>>> I kindly ask you to confirm if the currently normal descriptor
>>>>>> structure
>>>>>> (w/o your changes) doesn't work on your platform.
>>>>>> Did you test it?
>>>>>
>>>>> Well, the normal descriptor works on my platform except TX checksum
>>>>> offload.
>>>>
>>>> ok! I suspected that.
>>>>
>>>>
>>>>>>> Moreover, I want to enable the TX checksum offload function which is
>>>>>>> not supported in normal descriptor.
>>>>>>> Any suggestions?
>>>>>>
>>>>>> It is supported but you have to pass from the platform: tx_coe = 1.
>>>>>
>>>>> I noticed that the flag csum_insertion is passed to
>>>>> ndesc_prepare_tx_desc() in stmmac_xmit(). But ndesc_prepare_tx_desc()
>>>>> just ignores it.
>>>>> In other words, the TX checksum offload function is disabled in normal
>>>>> descriptor currently.
>>>>>
>>>>> Should we fix this problem for normal descriptor?
>>>>
>>>> Yes, we should. If you agree, I'll update the normal descriptor
>>>> structure to yours. This is the normal descriptor used in newer GMAC.
>>>> Tx csum will be done for normal descriptors in case of these GMAC
>>>> devices and not for old MAC10/100. For the MAC10/100 some bits for
>>>> normal descriptors are reserved and won't be used at all.
>>>>
>>>> I'll also verify that the patch doesn't break the back-compatibility
>>>> with old MAC10/100. I have the HW where doing the tests.
>>>>
>>>> After that, I'll prepare the patch for net-next and for your kernel.
>>>
>>> Hello Kelvin
>>>
>>> attached the patch tested on my development kernel.
>>> It runs fine on old and new mac devices.
>>>
>>> Can you try it on your side? Hmm, it is likely it won't apply fine on
>>> your tree but you know the changes ;-).
>>>
>>> If ok, I'll rework it for net-next and send it to the mailing list.
>>>
>>> Thanks
>>> Peppe
>>>
>>>>
>>>>>
>>>>>> Peppe
>>>>>>>
>>>>>>>> Note:
>>>>>>>> IIRC, there is a bit difference in case of normal descriptors for
>>>>>>>> Synopsys databook newer than the 1.91 (I used for testing this
>>>>>>>> mode).
>>>>>>>> In any case, I remember that, on some platforms, the normal
>>>>>>>> descriptors
>>>>>>>> have been used w/o problems also on these new chip generations.
>>>>>>>>
>>>>>>>> Peppe
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>> --
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>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>
>>>
>>>
>>
>>
>
>


-- 
Best Regards!
Kelvin

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