net: stmmac: fix get_hw_feature() on old hardware

commit 075da58 upstream.

Some old IPs do not provide the hardware feature register.
On these IPs, this register is read 0x00000000.

In old driver version, this feature was handled but a regression came
with the commit f10a6a3 ("stmmac: rework get_hw_feature function").
Indeed, this commit removes the return value in dma->get_hw_feature().
This return value was used to indicate the validity of retrieved
information and used later on in stmmac_hw_init() to override
priv->plat data if this hardware feature were valid.

This patch restores the return code in ->get_hw_feature() in order
to indicate the hardware feature validity and override priv->plat
data only if this hardware feature is valid.

Fixes: f10a6a3 ("stmmac: rework get_hw_feature function")
Signed-off-by: Herve Codina <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: hcodina

drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c

@@ -218,11 +218,18 @@ static void dwmac1000_dump_dma_regs(void __iomem *ioaddr, u32 *reg_space)
 				readl(ioaddr + DMA_BUS_MODE + i * 4);
 }
 
-static void dwmac1000_get_hw_feature(void __iomem *ioaddr,
-				     struct dma_features *dma_cap)
+static int dwmac1000_get_hw_feature(void __iomem *ioaddr,
+				    struct dma_features *dma_cap)
 {
 	u32 hw_cap = readl(ioaddr + DMA_HW_FEATURE);
 
+	if (!hw_cap) {
+		/* 0x00000000 is the value read on old hardware that does not
+		 * implement this register
+		 */
+		return -EOPNOTSUPP;
+	}
+
 	dma_cap->mbps_10_100 = (hw_cap & DMA_HW_FEAT_MIISEL);
 	dma_cap->mbps_1000 = (hw_cap & DMA_HW_FEAT_GMIISEL) >> 1;
 	dma_cap->half_duplex = (hw_cap & DMA_HW_FEAT_HDSEL) >> 2;
@@ -252,6 +259,8 @@ static void dwmac1000_get_hw_feature(void __iomem *ioaddr,
 	dma_cap->number_tx_channel = (hw_cap & DMA_HW_FEAT_TXCHCNT) >> 22;
 	/* Alternate (enhanced) DESC mode */
 	dma_cap->enh_desc = (hw_cap & DMA_HW_FEAT_ENHDESSEL) >> 24;
+
+	return 0;
 }
 
 static void dwmac1000_rx_watchdog(void __iomem *ioaddr, u32 riwt,

drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c

@@ -337,8 +337,8 @@ static void dwmac4_dma_tx_chan_op_mode(void __iomem *ioaddr, int mode,
 	writel(mtl_tx_op, ioaddr +  MTL_CHAN_TX_OP_MODE(channel));
 }
 
-static void dwmac4_get_hw_feature(void __iomem *ioaddr,
-				  struct dma_features *dma_cap)
+static int dwmac4_get_hw_feature(void __iomem *ioaddr,
+				 struct dma_features *dma_cap)
 {
 	u32 hw_cap = readl(ioaddr + GMAC_HW_FEATURE0);
 
@@ -425,6 +425,8 @@ static void dwmac4_get_hw_feature(void __iomem *ioaddr,
 	dma_cap->frpbs = (hw_cap & GMAC_HW_FEAT_FRPBS) >> 11;
 	dma_cap->frpsel = (hw_cap & GMAC_HW_FEAT_FRPSEL) >> 10;
 	dma_cap->dvlan = (hw_cap & GMAC_HW_FEAT_DVLAN) >> 5;
+
+	return 0;
 }
 
 /* Enable/disable TSO feature and set MSS */

drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c

@@ -365,8 +365,8 @@ static int dwxgmac2_dma_interrupt(void __iomem *ioaddr,
 	return ret;
 }
 
-static void dwxgmac2_get_hw_feature(void __iomem *ioaddr,
-				    struct dma_features *dma_cap)
+static int dwxgmac2_get_hw_feature(void __iomem *ioaddr,
+				   struct dma_features *dma_cap)
 {
 	u32 hw_cap;
 
@@ -439,6 +439,8 @@ static void dwxgmac2_get_hw_feature(void __iomem *ioaddr,
 	dma_cap->frpes = (hw_cap & XGMAC_HWFEAT_FRPES) >> 11;
 	dma_cap->frpbs = (hw_cap & XGMAC_HWFEAT_FRPPB) >> 9;
 	dma_cap->frpsel = (hw_cap & XGMAC_HWFEAT_FRPSEL) >> 3;
+
+	return 0;
 }
 
 static void dwxgmac2_rx_watchdog(void __iomem *ioaddr, u32 riwt, u32 nchan)

drivers/net/ethernet/stmicro/stmmac/hwif.h

@@ -203,8 +203,8 @@ struct stmmac_dma_ops {
 	int (*dma_interrupt) (void __iomem *ioaddr,
 			      struct stmmac_extra_stats *x, u32 chan);
 	/* If supported then get the optional core features */
-	void (*get_hw_feature)(void __iomem *ioaddr,
-			       struct dma_features *dma_cap);
+	int (*get_hw_feature)(void __iomem *ioaddr,
+			      struct dma_features *dma_cap);
 	/* Program the HW RX Watchdog */
 	void (*rx_watchdog)(void __iomem *ioaddr, u32 riwt, u32 number_chan);
 	void (*set_tx_ring_len)(void __iomem *ioaddr, u32 len, u32 chan);
@@ -255,7 +255,7 @@ struct stmmac_dma_ops {
 #define stmmac_dma_interrupt_status(__priv, __args...) \
 	stmmac_do_callback(__priv, dma, dma_interrupt, __args)
 #define stmmac_get_hw_feature(__priv, __args...) \
-	stmmac_do_void_callback(__priv, dma, get_hw_feature, __args)
+	stmmac_do_callback(__priv, dma, get_hw_feature, __args)
 #define stmmac_rx_watchdog(__priv, __args...) \
 	stmmac_do_void_callback(__priv, dma, rx_watchdog, __args)
 #define stmmac_set_tx_ring_len(__priv, __args...) \