[PATCH] ARM: stm32: Add additional ID register check for KSZ8851 presence

[Marek Vasut]

Currently the code sets eth1addr only if /ethernet1 alias exists in DT,
the node pointed to by the alias has "micrel,ks8851-mll" compatible
string, and the KSZ8851 CCR register read indicates programmed EEPROM
is not connected.

This is not sufficient to detect cases where the DT still contains the
KSZ8851 nodes, but the chip itself is not present. Extend the detection
to handle these cases.

Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Patrice Chotard <patrice.chotard at foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay at foss.st.com>
---
 board/dhelectronics/dh_stm32mp1/board.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/board/dhelectronics/dh_stm32mp1/board.c b/board/dhelectronics/dh_stm32mp1/board.c
index 49b12c4c042..ac1af718d4a 100644
--- a/board/dhelectronics/dh_stm32mp1/board.c
+++ b/board/dhelectronics/dh_stm32mp1/board.c
@@ -86,6 +86,8 @@ DECLARE_GLOBAL_DATA_PTR;
 #define KS_CCR_EEPROM	BIT(9)
 #define KS_BE0		BIT(12)
 #define KS_BE1		BIT(13)
+#define KS_CIDER	0xC0
+#define CIDER_ID	0x8870
 
 int setup_mac_address(void)
 {
@@ -123,11 +125,18 @@ int setup_mac_address(void)
 	 * is present. If EEPROM is present, it must contain valid
 	 * MAC address.
 	 */
-	u32 reg, ccr;
+	u32 reg, cider, ccr;
 	reg = fdt_get_base_address(gd->fdt_blob, off);
 	if (!reg)
 		goto out_set_ethaddr;
 
+	writew(KS_BE0 | KS_BE1 | KS_CIDER, reg + 2);
+	cider = readw(reg);
+	if ((cider & 0xfff0) != CIDER_ID) {
+		skip_eth1 = true;
+		goto out_set_ethaddr;
+	}
+
 	writew(KS_BE0 | KS_BE1 | KS_CCR, reg + 2);
 	ccr = readw(reg);
 	if (ccr & KS_CCR_EEPROM) {
-- 
2.30.2