[PATCH v4] hw/net/imx_fec: write TGSR and TCSR3 in imx_enet_write()

[Chen Qun]

The current code causes clang static code analyzer generate warning:
hw/net/imx_fec.c:858:9: warning: Value stored to 'value' is never read
        value = value & 0x0000000f;
        ^       ~~~~~~~~~~~~~~~~~~
hw/net/imx_fec.c:864:9: warning: Value stored to 'value' is never read
        value = value & 0x000000fd;
        ^       ~~~~~~~~~~~~~~~~~~

According to the definition of the function, the two “value” assignments
 should be written to registers.

Reported-by: Euler Robot <address@hidden>
Signed-off-by: Chen Qun <address@hidden>
---
Cc: Peter Maydell <address@hidden>
Cc: Jason Wang <address@hidden>
Cc: Peter Chubb <address@hidden>

v1->v2:
  The register 'ENET_TGSR' write-1-to-clear timer flag.
  The register 'ENET_TCSRn' 7bit(TF) write-1-to-clear timer flag.

v2->v3:
  Optimize code style, based on discussions with Peter.

v3->v4:
  Delete reserved bits write zero(Base on Peter's comments).
---
 hw/net/imx_fec.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/net/imx_fec.c b/hw/net/imx_fec.c
index 6a124a154a..5c145a8197 100644
--- a/hw/net/imx_fec.c
+++ b/hw/net/imx_fec.c
@@ -855,13 +855,15 @@ static void imx_enet_write(IMXFECState *s, uint32_t 
index, uint32_t value)
         break;
     case ENET_TGSR:
         /* implement clear timer flag */
-        value = value & 0x0000000f;
+        s->regs[index] &= ~(value & 0x0000000f); /* all bits W1C */
         break;
     case ENET_TCSR0:
     case ENET_TCSR1:
     case ENET_TCSR2:
     case ENET_TCSR3:
-        value = value & 0x000000fd;
+        s->regs[index] &= ~(value & 0x00000080); /* W1C bits */
+        s->regs[index] &= ~0x0000007d; /* writable fields */
+        s->regs[index] |= (value & 0x0000007d);
         break;
     case ENET_TCCR0:
     case ENET_TCCR1:
-- 
2.23.0