[PATCH] net: eqos: let phy_resume handle fixed link phys

[Rouven Czerwinski]

Currently barebox will try to talk to the phy over mdio, even if the
parent is a fixed-link. This will result in the following stacktrace:

  barebox at Linux Automation Test Automation Controller (TAC):/ dhcp
  unable to handle NULL pointer dereference at address 0x00000130
  pc : [<dfc01800>]    lr : [<dfc0f963>]
  sp : dffefd40  ip : 004c4b40  fp : d00286e0
  r10: cf25cc4e  r9 : 00000000  r8 : 05f5e100
  r7 : 00000130  r6 : 00000000  r5 : 00000000  r4 : 00000130
  r3 : 00000109  r2 : 00000000  r1 : 00000000  r0 : 00000130
  Flags: nZCv  IRQs off  FIQs off  Mode SVC_32
  WARNING: [<dfc01800>] (slice_acquire+0xc/0x28) from [<dfc0f963>] (mdiobus_read+0x13/0x28)
  WARNING: [<dfc0f963>] (mdiobus_read+0x13/0x28) from [<dfc10685>] (eqos_start+0x85/0x32c)
  WARNING: [<dfc10685>] (eqos_start+0x85/0x32c) from [<dfc3cdf1>] (eth_open+0xd/0x24)
  WARNING: [<dfc3cdf1>] (eth_open+0xd/0x24) from [<dfc3e391>] (dhcp+0xb/0x3a)
  WARNING: [<dfc3e391>] (dhcp+0xb/0x3a) from [<dfc30fab>] (do_dhcp+0xfb/0x114)
  WARNING: [<dfc30fab>] (do_dhcp+0xfb/0x114) from [<dfc0490f>] (execute_command+0x23/0x4c)
  WARNING: [<dfc0490f>] (execute_command+0x23/0x4c) from [<dfc0a127>] (run_list_real+0x5bf/0x638)
  WARNING: [<dfc0a127>] (run_list_real+0x5bf/0x638) from [<dfc09a2b>] (parse_stream_outer+0xc7/0x154)
  WARNING: [<dfc09a2b>] (parse_stream_outer+0xc7/0x154) from [<dfc0a383>] (run_shell+0x3f/0x6c)
  WARNING: [<dfc0a383>] (run_shell+0x3f/0x6c) from [<dfc010b9>] (run_init+0x191/0x200)
  WARNING: [<dfc010b9>] (run_init+0x191/0x200) from [<dfc01153>] (start_barebox+0x2b/0x6c)
  WARNING: [<dfc01153>] (start_barebox+0x2b/0x6c) from [<dfc4be6d>] (barebox_non_pbl_start+0x121/0x164)
  WARNING: [<dfc4be6d>] (barebox_non_pbl_start+0x121/0x164) from [<dfc00005>] (__bare_init_start+0x1/0xc)

  WARNING: [<dfc4da7d>] (unwind_backtrace+0x1/0x78) from [<dfc01461>] (panic+0x1d/0x34)
  WARNING: [<dfc01461>] (panic+0x1d/0x34) from [<dfc4b6a3>] (do_exception+0xf/0x14)
  WARNING: [<dfc4b6a3>] (do_exception+0xf/0x14) from [<dfc4b711>] (do_data_abort+0x21/0x34)
  WARNING: [<dfc4b711>] (do_data_abort+0x21/0x34) from [<dfc4b454>] (do_abort_6+0x48/0x54)

Simply return with 0 if bus is zero which indicates that the phy is
connected to a fixed link.

Signed-off-by: Rouven Czerwinski <r.czerwinski at pengutronix.de>
---
 drivers/net/designware_eqos.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/designware_eqos.c b/drivers/net/designware_eqos.c
index f83ec12714..f83e5d6d9b 100644
--- a/drivers/net/designware_eqos.c
+++ b/drivers/net/designware_eqos.c
@@ -362,6 +362,10 @@ static int phy_resume(struct phy_device *phydev)
 {
 	int bmcr;
 
+	// Bus will be NULL if a fixed-link is used.
+	if (!phydev->bus)
+		return 0;
+
 	bmcr = phy_read(phydev, MII_BMCR);
 	if (bmcr < 0)
 		return bmcr;
-- 
2.32.0