Re: [PATCH 3/3] dp8393x: fix receiving buffer exhaustion

[Hervé Poussineau]

Le 02/11/2019 à 18:15, Laurent Vivier a écrit :

The card is not able to exit from exhaustion state, because
while the drive consumes the buffers, the RRP is incremented
(when the driver clears the ISR RBE bit), so it stays equal
to RWP, and while RRP == RWP, the card thinks it is always
in exhaustion state. So the driver consumes all the buffers,
but the card cannot receive new ones.

This patch fixes the problem by not incrementing RRP when
the driver clears the ISR RBE bit.

Signed-off-by: Laurent Vivier <laur...@vivier.eu>
---
  hw/net/dp8393x.c | 31 ++++++++++++++++---------------
  1 file changed, 16 insertions(+), 15 deletions(-)

I checked the DP83932C specification, available at
https://www.eit.lth.se/fileadmin/eit/courses/datablad/Periphery/Communication/DP83932C.pdf

In the Buffer Resources Exhausted section (page 20):
"To continue reception after the last RBA is used, the system must supply
additional RRA descriptor(s), update the RWP register, and clear the RBE
bit in the ISR. The SONIC rereads the RRA after this bit is cleared."

If I understand correctly, if the OS updates first the RWP and then clear the 
RBE bit,
then RRP should be different of RWP in dp8393x_do_read_rra() ? Or did I miss 
something?

diff --git a/hw/net/dp8393x.c b/hw/net/dp8393x.c
index b8c4473f99..21deb32456 100644
--- a/hw/net/dp8393x.c
+++ b/hw/net/dp8393x.c
@@ -304,7 +304,7 @@ static void dp8393x_do_load_cam(dp8393xState *s)
      dp8393x_update_irq(s);
  }

-static void dp8393x_do_read_rra(dp8393xState *s)

+static void dp8393x_do_read_rra(dp8393xState *s, int next)
  {
      int width, size;

@@ -323,19 +323,20 @@ static void dp8393x_do_read_rra(dp8393xState *s)

          s->regs[SONIC_CRBA0], s->regs[SONIC_CRBA1],
          s->regs[SONIC_RBWC0], s->regs[SONIC_RBWC1]);

- /* Go to next entry */

-    s->regs[SONIC_RRP] += size;
+    if (next) {
+        /* Go to next entry */
+        s->regs[SONIC_RRP] += size;

- /* Handle wrap */

-    if (s->regs[SONIC_RRP] == s->regs[SONIC_REA]) {
-        s->regs[SONIC_RRP] = s->regs[SONIC_RSA];
-    }
+        /* Handle wrap */
+        if (s->regs[SONIC_RRP] == s->regs[SONIC_REA]) {
+            s->regs[SONIC_RRP] = s->regs[SONIC_RSA];
+        }

- /* Check resource exhaustion */

-    if (s->regs[SONIC_RRP] == s->regs[SONIC_RWP])
-    {
-        s->regs[SONIC_ISR] |= SONIC_ISR_RBE;
-        dp8393x_update_irq(s);
+        /* Check resource exhaustion */
+        if (s->regs[SONIC_RRP] == s->regs[SONIC_RWP]) {
+            s->regs[SONIC_ISR] |= SONIC_ISR_RBE;
+            dp8393x_update_irq(s);
+        }
      }

/* Done */

@@ -549,7 +550,7 @@ static void dp8393x_do_command(dp8393xState *s, uint16_t 
command)
      if (command & SONIC_CR_RST)
          dp8393x_do_software_reset(s);
      if (command & SONIC_CR_RRRA)
-        dp8393x_do_read_rra(s);
+        dp8393x_do_read_rra(s, 1);
      if (command & SONIC_CR_LCAM)
          dp8393x_do_load_cam(s);
  }
@@ -640,7 +641,7 @@ static void dp8393x_write(void *opaque, hwaddr addr, 
uint64_t data,
              data &= s->regs[reg];
              s->regs[reg] &= ~data;
              if (data & SONIC_ISR_RBE) {
-                dp8393x_do_read_rra(s);
+                dp8393x_do_read_rra(s, 0);
              }
              dp8393x_update_irq(s);
              if (dp8393x_can_receive(s->nic->ncs)) {
@@ -840,7 +841,7 @@ static ssize_t dp8393x_receive(NetClientState *nc, const 
uint8_t * buf,

if (s->regs[SONIC_RCR] & SONIC_RCR_LPKT) {

              /* Read next RRA */
-            dp8393x_do_read_rra(s);
+            dp8393x_do_read_rra(s, 1);
          }
      }