On Fri, Aug 12, 2016 at 4:55 PM, Stephen Warren swarren@wwwdotorg.org wrote:
On 08/04/2016 03:48 PM, Joe Hershberger wrote:
On Thu, Aug 4, 2016 at 4:34 PM, Joe Hershberger joe.hershberger@gmail.com wrote:
On Thu, Aug 4, 2016 at 4:22 PM, Joe Hershberger joe.hershberger@gmail.com wrote:
Hi Stephen,
On Tue, Aug 2, 2016 at 11:56 AM, Stephen Warren swarren@wwwdotorg.org wrote:
On 08/01/2016 09:20 PM, Peter Chubb wrote:
Hi Folks, Since patch 96350f729c42 "dm: tegra: net: Convert tegra boards to driver model for Ethernet" booting via dhcp has been broken on the Jetson TK1.
...
I believe the correct approach is for the caller (network core code) to provide cache-aligned buffers, rather than for each driver to align the start/size when performing cache operations. Again, this is to ensure that cache operations don't affect any other data adjacent to the buffer. Can you see why the network core code isn't using cache-aligned buffers when DM_ETH is enabled? Perhaps DM_ETH isn't the trigger, but just changed something about the memory layout that exposed some other pre-existing issue.
This should already be the case. The transmit buffer is setup like this:
net_tx_packet = &net_pkt_buf[0] + (PKTALIGN - 1); net_tx_packet -= (ulong)net_tx_packet % PKTALIGN;in net/net.c:net_init().
The recv buffers are defined by the drivers and passed back to the core network code. In this case, the misalignment is caused by the rtl8169 driver...
rtl8169_init_ring() does this:
tpc->RxBufferRing[i] = &rxb[i * RX_BUF_SIZE];...but the size breaks alignment for all but the first entry:
#define RX_BUF_SIZE 1536 /* Rx Buffer size */This should be fixed by defining this instead:
#define RX_BUF_SIZE ALIGN(1536, RTL8169_ALIGN) /* RxBuffer size */
Also, there is an extra buffer that is memcpy'ed to, and then that is passed back to the core net code instead of the actual buffer that was recv'd into; I don't know why:
static unsigned char rxdata[RX_BUF_LEN];I also noticed that the code to setup the tx ring buffers are completely wrong. It's a good thing that NUM_TX_DESC is defined to be
From rtl8169_init_ring():
for (i = 0; i < NUM_TX_DESC; i++) { tpc->Tx_skbuff[i] = &txb[i]; }That would set the buffer not only to be unaligned after the index 0, but also to be one byte after the previous, thus they would all stomp on each other.
It should be:
tpc->Tx_skbuff[i] = &txb[i * RX_BUF_SIZE];It's probably also worth making another define for TX_BUF_SIZE even if it is just defined to RX_BUF_SIZE to keep it from looking like a bug.
Essentially this patch was incomplete; only ensuring that the first of the buffers in each ring were aligned:
Joe and Peter, do you expect to send a patch to fix these issues, or were you hoping I would? If you're waiting on me, it won't be quick; too many other cleanups and fixes stacked up right now...
I'm working on it.
Cheers, -Joe