Hi,

Le 04/05/2026 à 17:56, Holger Brunck a écrit :
If dma_rmb is used it has to be done after reading bd_status and checking
if R_E_S is zero. Therefore we need to move it into the while loop.

Can you give more details ? Why does dma_rmb() has to be done after reading bd_status and checking if R_E_S is zero ?


Fixes: c19b6d246a35 ("drivers/net: support hdlc function for QE-UCC")
Signed-off-by: Holger Brunck <[email protected]>
---
  drivers/net/wan/fsl_ucc_hdlc.c | 3 +--
  1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/wan/fsl_ucc_hdlc.c b/drivers/net/wan/fsl_ucc_hdlc.c
index 15bfb78381d4..09081f128a98 100644
--- a/drivers/net/wan/fsl_ucc_hdlc.c
+++ b/drivers/net/wan/fsl_ucc_hdlc.c
@@ -523,12 +523,12 @@ static int hdlc_rx_done(struct ucc_hdlc_private *priv, 
int rx_work_limit)
        u16 length, howmany = 0;
        u8 *bdbuffer;
- dma_rmb();
        bd = priv->currx_bd;
        bd_status = be16_to_cpu(bd->status);
/* while there are received buffers and BD is full (~R_E) */
        while (!((bd_status & (R_E_S)) || (--rx_work_limit < 0))) {
+               dma_rmb();
                if (bd_status & (RX_BD_ERRORS)) {
                        dev->stats.rx_errors++;
@@ -610,7 +610,6 @@ static int hdlc_rx_done(struct ucc_hdlc_private *priv, int rx_work_limit) bd_status = be16_to_cpu(bd->status);
        }
-       dma_rmb();
priv->currx_bd = bd;
        return howmany;


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