Re: [PATCH] hw/dma/xilinx_axidma: Check DMASR.HALTED to prevent infinite loop.

[Tommy Wu]

Thank Edgar E. Iglesias for the advice.
I can submit another patch to do that.

On Fri, May 19, 2023 at 2:39 PM Edgar E. Iglesias <edgar.iglesias@gmail.com> wrote:

On Fri, May 19, 2023 at 8:21 AM Tommy Wu <tommy.wu@sifive.com> wrote:

When we receive a packet from the xilinx_axienet and then try to s2mem
through the xilinx_axidma, if the descriptor ring buffer is full in the
xilinx axidma driver, we’ll assert the DMASR.HALTED in the
function : stream_process_s2mem and return 0. In the end, we’ll be stuck in
an infinite loop in axienet_eth_rx_notify.

This patch checks the DMASR.HALTED state when we try to push data
from xilinx axi-enet to xilinx axi-dma. When the DMASR.HALTED is asserted,
we will not keep pushing the data and then prevent the infinte loop.

Signed-off-by: Tommy Wu <tommy.wu@sifive.com>
---
 hw/dma/xilinx_axidma.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/hw/dma/xilinx_axidma.c b/hw/dma/xilinx_axidma.c
index 6030c76435..12c90267df 100644
--- a/hw/dma/xilinx_axidma.c
+++ b/hw/dma/xilinx_axidma.c
@@ -168,6 +168,11 @@ static inline int stream_idle(struct Stream *s)
     return !!(s->regs[R_DMASR] & DMASR_IDLE);
 }

+static inline int stream_halted(struct Stream *s)

At some point we should probably change all of these helpers to return booleans...

Anyway, this fix looks good to me:

Reviewed-by: Edgar E. Iglesias <edgar@zeroasic.com>

 

+{
+    return !!(s->regs[R_DMASR] & DMASR_HALTED);
+}
+
 static void stream_reset(struct Stream *s)
 {
     s->regs[R_DMASR] = DMASR_HALTED;  /* starts up halted.  */
@@ -269,7 +274,7 @@ static void stream_process_mem2s(struct Stream *s, StreamSink *tx_data_dev,
     uint64_t addr;
     bool eop;

-    if (!stream_running(s) || stream_idle(s)) {
+    if (!stream_running(s) || stream_idle(s) || stream_halted(s)) {
         return;
     }

@@ -326,7 +331,7 @@ static size_t stream_process_s2mem(struct Stream *s, unsigned char *buf,
     unsigned int rxlen;
     size_t pos = 0;

-    if (!stream_running(s) || stream_idle(s)) {
+    if (!stream_running(s) || stream_idle(s) || stream_halted(s)) {
         return 0;
     }

@@ -407,7 +412,7 @@ xilinx_axidma_data_stream_can_push(StreamSink *obj,
     XilinxAXIDMAStreamSink *ds = XILINX_AXI_DMA_DATA_STREAM(obj);
     struct Stream *s = &ds->dma->streams[1];

-    if (!stream_running(s) || stream_idle(s)) {
+    if (!stream_running(s) || stream_idle(s) || stream_halted(s)) {
         ds->dma->notify = notify;
         ds->dma->notify_opaque = notify_opaque;
         return false;
--
2.31.1