On Mon, Apr 28, 2014 at 2:08 AM, Marek Vasut <ma...@denx.de> wrote: > On Sunday, April 27, 2014 at 05:29:29 PM, Chen-Yu Tsai wrote: >> On Sun, Apr 27, 2014 at 11:25 PM, Ian Campbell <i...@hellion.org.uk> wrote: >> > On Sat, 2014-04-26 at 20:28 +0200, Marek Vasut wrote: >> >> On Friday, April 18, 2014 at 08:05:50 PM, Ian Campbell wrote: >> >> > From: Jens Kuske <jensku...@gmail.com> >> >> > >> >> > The GMAC module in Allwinner sunxi SoCs seems to have problems with >> >> > burst lengths > 8. >> >> >> >> Is there any explanation for the problems please ? >> > >> > Jens or Wens, can you answer this? >> >> IIRC, with burst lengths > 8, GMAC doesn't work, no ping, no DHCP. >> I don't remember if it was TX or RX that suffered, or even both. >> >> Hope this clarifies things a bit. > > No, it does not at all, sorry. What you describe are symptoms, but what I want > to know is what is the root cause of those symptoms. You did not explain that.
I can not offer much more explanation. The value was hardcoded in Allwinner's code. The datasheets don't offer much, except this line might be related: (DMA) Descriptor architecture, allowing large blocks of data transfer with minimum CPU intervention; each descriptor can transfer up to 4 KB data. Also probably related: 4KB TX FIFO for transmission packets and 16KB RX FIFO for reception packets. I'm not an expert in hardware. We could ask Allwinner, but given past inquiries from the linux-sunxi community, I'd say getting a reply on hardware specifics is unlikely to happen. So my guess is that this is limited by the DWMAC IP Allwinner licensed from Synopsys. Cheers ChenYu _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
