detect if the bus is swapped and report a 32bit drivers is used on a 16bit bus

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <[email protected]>
---
 drivers/net/smc911x.c |   21 ++++++++++++++++++++-
 drivers/net/smc911x.h |    2 ++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/net/smc911x.c b/drivers/net/smc911x.c
index 75a332e..8528527 100644
--- a/drivers/net/smc911x.c
+++ b/drivers/net/smc911x.c
@@ -470,9 +470,28 @@ static int smc911x_probe(struct device_d *dev)
        }
 
        val = smc911x_reg_read(priv, BYTE_TEST);
-       if(val != 0x87654321) {
+       if (val == 0x43218765) {
+               dev_dbg(dev, "BYTE_TEST looks swapped, "
+                          "applying WORD_SWAP");
+               smc911x_reg_write(priv, WORD_SWAP, 0xffffffff);
+
+               /* 1 dummy read of BYTE_TEST is needed after a write to
+                * WORD_SWAP before its contents are valid */
+               val = smc911x_reg_read(priv, BYTE_TEST);
+
+               val = smc911x_reg_read(priv, BYTE_TEST);
+       }
+
+       if (val != 0x87654321) {
                dev_err(dev, "no smc911x found on 0x%p (byte_test=0x%08x)\n",
                        priv->base, val);
+               if (((val >> 16) & 0xFFFF) == (val & 0xFFFF)) {
+                       /*
+                        * This may mean the chip is set
+                        * for 32 bit while the bus is reading 16 bit
+                        */
+                       dev_err(dev, "top 16 bits equal to bottom 16 bits\n");
+               }
                return -ENODEV;
        }
 
diff --git a/drivers/net/smc911x.h b/drivers/net/smc911x.h
index baf3598..d409247 100644
--- a/drivers/net/smc911x.h
+++ b/drivers/net/smc911x.h
@@ -26,6 +26,8 @@
  * of the Lan911x memory space
  */
 
+#define WORD_SWAP              0x98
+
 #define RX_DATA_FIFO            0x00
 
 #define TX_DATA_FIFO            0x20
-- 
1.7.10.4


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