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

[Marek Vasut]

Dear 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.

Thank you, that'd be really nice of you to do.

Best regards,
Marek Vasut