[U-Boot] [PATCH v2 05/18] pcnet: enable the NOUFLO feature

[Paul Burton]

On 10/11/13 20:02, Marek Vasut wrote:
> Dear Paul Burton,
>
>> On relatively slow boards (such as the MIPS Malta with an FPGA core
>> card) it can be extremely common for transmits to underflow - to the
>> point where it appears they simply do not work at all. Setting the
>> NOUFLO bit causes the ethernet controller to not begin transmission on
>> the wire until a transmit start point is reached. Setting that transmit
>> start point to the full packet will cause the controller to only
>> transmit the packet once it has buffered it entirely thus preventing any
>> transmit underflows from occuring and allowing the controller to
>> function on slower boards.
>>
>> Signed-off-by: Paul Burton <paul.burton at imgtec.com>
>> ---
>> Changes in v2:
>>    - rebase atop master
>> ---
>>   drivers/net/pcnet.c | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/drivers/net/pcnet.c b/drivers/net/pcnet.c
>> index 7b87660..5b248be 100644
>> --- a/drivers/net/pcnet.c
>> +++ b/drivers/net/pcnet.c
>> @@ -312,6 +312,21 @@ static int pcnet_init(struct eth_device *dev, bd_t
>> *bis) pcnet_write_bcr(dev, 32, val);
>>
>>   	/*
>> +	 * Enable NOUFLO on supported controllers, with the transmit
>> +	 * start point set to the full packet. This will cause entire
>> +	 * packets to be buffered by the ethernet controller before
>> +	 * transmission, eliminating underflows which are common on
>> +	 * slower devices. Controllers which do not support NOUFLO will
>> +	 * simply be left with a larger transmit FIFO threshold.
>> +	 */
>> +	val = pcnet_read_bcr(dev, 18);
>> +	val |= 1 << 11;
>> +	pcnet_write_bcr(dev, 18, val);
>> +	val = pcnet_read_csr(dev, 80);
>> +	val |= 0x3 << 10;
>> +	pcnet_write_csr(dev, 80, val);
>
> Would be nice to fix this so we don't have so many magic numbers there.
>
> Best regards,
> Marek Vasut
>

I agree, the whole file is full of them. I'll submit a cleanup patch 
later if nobody else beats me to it.

Thanks,
     Paul