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Re: [Qemu-devel] [PATCH v2] net: cadence_gem: clear RX control descripto

From: Jason Wang
Subject: Re: [Qemu-devel] [PATCH v2] net: cadence_gem: clear RX control descriptor
Date: Tue, 16 Jul 2019 19:58:22 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2

On 2019/7/16 下午6:59, Ramon Fried wrote:
The RX ring descriptors control field is used for setting
SOF and EOF (start of frame and end of frame).
The SOF and EOF weren't cleared from the previous descriptors,
causing inconsistencies in ring buffer.
Fix that by clearing the control field of every descriptors we're

Signed-off-by: Ramon Fried <address@hidden>
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

   * change function name to rx_desc_clear_control as proposed by
     Jason Wang
   * Move the function call above the comment, as proposed by
     Philippe Mathieu-Daudé

  hw/net/cadence_gem.c | 7 +++++++
  1 file changed, 7 insertions(+)

diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c
index ecee22525c..cca3ce7f56 100644
--- a/hw/net/cadence_gem.c
+++ b/hw/net/cadence_gem.c
@@ -406,6 +406,11 @@ static inline void rx_desc_set_sof(uint32_t *desc)
      desc[1] |= DESC_1_RX_SOF;
+static inline void rx_desc_clear_control(uint32_t *desc)
+    desc[1]  = 0;
  static inline void rx_desc_set_eof(uint32_t *desc)
      desc[1] |= DESC_1_RX_EOF;
@@ -993,6 +998,8 @@ static ssize_t gem_receive(NetClientState *nc, const 
uint8_t *buf, size_t size)
          rxbuf_ptr += MIN(bytes_to_copy, rxbufsize);
          bytes_to_copy -= MIN(bytes_to_copy, rxbufsize);
+ rx_desc_clear_control(s->rx_desc[q]);
          /* Update the descriptor.  */
          if (first_desc) {



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