[PATCH net-next v2 2/9] net: stmmac: dwmac4: fix RX FIFO fill statistics

[Russell King (Oracle)]

In dwmac4_debug(), the wrong shift is used with the RXFSTS mask:

 #define MTL_DEBUG_RXFSTS_MASK          GENMASK(5, 4)
 #define MTL_DEBUG_RXFSTS_SHIFT         4
 #define MTL_DEBUG_RRCSTS_SHIFT         1

                       u32 rxfsts = (value & MTL_DEBUG_RXFSTS_MASK)
                                    >> MTL_DEBUG_RRCSTS_SHIFT;

where rxfsts is tested against small integers 1 .. 3. This results in
the tests always failing, causing the "mtl_rx_fifo__fill_level_empty"
statistic counter to always be incremented no matter what the fill
level actually is.

Fix this by using FIELD_GET() and remove the unnecessary
MTL_DEBUG_RXFSTS_SHIFT definition as FIELD_GET() will shift according
to the least siginificant set bit in the supplied field mask.

Reviewed-by: Maxime Chevallier <maxime.chevallier at bootlin.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel at armlinux.org.uk>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4.h      | 1 -
 drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c | 3 +--
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
index fa27639895ce..3da6891b9df7 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
@@ -460,7 +460,6 @@ static inline u32 mtl_low_credx_base_addr(const struct dwmac4_addrs *addrs,
 
 /* MAC debug: GMII or MII Transmit Protocol Engine Status */
 #define MTL_DEBUG_RXFSTS_MASK		GENMASK(5, 4)
-#define MTL_DEBUG_RXFSTS_SHIFT		4
 #define MTL_DEBUG_RXFSTS_EMPTY		0
 #define MTL_DEBUG_RXFSTS_BT		1
 #define MTL_DEBUG_RXFSTS_AT		2
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
index a4282fd7c3c7..bd5f48d0b9fc 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
@@ -700,8 +700,7 @@ static void dwmac4_debug(struct stmmac_priv *priv, void __iomem *ioaddr,
 		value = readl(ioaddr + MTL_CHAN_RX_DEBUG(dwmac4_addrs, queue));
 
 		if (value & MTL_DEBUG_RXFSTS_MASK) {
-			u32 rxfsts = (value & MTL_DEBUG_RXFSTS_MASK)
-				     >> MTL_DEBUG_RRCSTS_SHIFT;
+			u32 rxfsts = FIELD_GET(MTL_DEBUG_RXFSTS_MASK, value);
 
 			if (rxfsts == MTL_DEBUG_RXFSTS_FULL)
 				x->mtl_rx_fifo_fill_level_full++;
-- 
2.47.3