[PATCH 3/7] net/ixgbe: Check that SFF-8472 soft rate select is supported before write

[Stephen Douthit <stephend@silicom-usa.com>]

Make sure an SFP is really a SFF-8472 device that supports the optional
soft rate select feature before just blindly poking those I2C registers.

Skip all I2C traffic if we know there's no SFP.

Fixes: f3430431aba ("ixgbe/base: add SFP+ dual-speed support")
Cc: stable@dpdk.org

Signed-off-by: Stephen Douthit <stephend@silicom-usa.com>
---
 drivers/net/ixgbe/base/ixgbe_common.c | 46 +++++++++++++++++++++++++++
 drivers/net/ixgbe/base/ixgbe_phy.h    |  3 ++
 2 files changed, 49 insertions(+)

diff --git a/drivers/net/ixgbe/base/ixgbe_common.c b/drivers/net/ixgbe/base/ixgbe_common.c
index 2764cf7cf1..3be1cc7fa2 100644
--- a/drivers/net/ixgbe/base/ixgbe_common.c
+++ b/drivers/net/ixgbe/base/ixgbe_common.c
@@ -5371,6 +5371,7 @@ s32 ixgbe_setup_mac_link_multispeed_fiber(struct ixgbe_hw *hw,
 void ixgbe_set_soft_rate_select_speed(struct ixgbe_hw *hw,
 					ixgbe_link_speed speed)
 {
+	enum ixgbe_sfp_cage_status sfp_cage_status;
 	s32 status;
 	u8 rs, eeprom_data;
 
@@ -5387,6 +5388,51 @@ void ixgbe_set_soft_rate_select_speed(struct ixgbe_hw *hw,
 		return;
 	}
 
+	/* Can't set rate on missing devices, skip all I2C access */
+	sfp_cage_status = ixgbe_check_sfp_cage(hw);
+	if (sfp_cage_status == IXGBE_SFP_CAGE_EMPTY ||
+	    sfp_cage_status == IXGBE_SFP_CAGE_NOCAGE) {
+		DEBUGOUT("No SFP\n");
+		return;
+	}
+
+	/* This only applies to SFF-8472 devices, so check that this device has
+	 * a non-zero SFF8472 compliance code @ device 0xA0 byte 94
+	 */
+	status = hw->phy.ops.read_i2c_eeprom(hw,
+					     IXGBE_SFF_SFF_8472_COMP,
+					     &eeprom_data);
+	if (status || !eeprom_data) {
+		DEBUGOUT("Not a SFF-8472 device\n");
+		goto out;
+	}
+
+	/* (read|write)_i2c_byte() don't support the address change mechanism
+	 * outlined in section 8.9 "Addressing Modes" of SFF_8472, so if that
+	 * is a requirement give up
+	 */
+	status = hw->phy.ops.read_i2c_eeprom(hw,
+					     IXGBE_SFF_SFF_8472_SWAP,
+					     &eeprom_data);
+	if (status || (eeprom_data & IXGBE_SFF_ADDRESSING_MODE)) {
+		DEBUGOUT("Address change not supported\n");
+		goto out;
+	}
+	/* Digital diagnostic monitoring must be supported for rate select */
+	if (!(eeprom_data & IXGBE_SFF_DDM_IMPLEMENTED)) {
+		DEBUGOUT("DDM not implemented\n");
+		goto out;
+	}
+
+	/* Finally check if the optional rate select feature is implemented */
+	status = hw->phy.ops.read_i2c_eeprom(hw,
+					     IXGBE_SFF_SFF_8472_EOPT,
+					     &eeprom_data);
+	if (status || !(eeprom_data & IXGBE_SFF_HAVE_RS)) {
+		DEBUGOUT("Rate select not supported");
+		goto out;
+	}
+
 	/* Set RS0 */
 	status = hw->phy.ops.read_i2c_byte(hw, IXGBE_SFF_SFF_8472_OSCB,
 					   IXGBE_I2C_EEPROM_DEV_ADDR2,
diff --git a/drivers/net/ixgbe/base/ixgbe_phy.h b/drivers/net/ixgbe/base/ixgbe_phy.h
index ceefbb3e68..cd57ce040f 100644
--- a/drivers/net/ixgbe/base/ixgbe_phy.h
+++ b/drivers/net/ixgbe/base/ixgbe_phy.h
@@ -21,6 +21,7 @@
 #define IXGBE_SFF_CABLE_TECHNOLOGY	0x8
 #define IXGBE_SFF_CABLE_SPEC_COMP	0x3C
 #define IXGBE_SFF_SFF_8472_SWAP		0x5C
+#define IXGBE_SFF_SFF_8472_EOPT		0x5D
 #define IXGBE_SFF_SFF_8472_COMP		0x5E
 #define IXGBE_SFF_SFF_8472_OSCB		0x6E
 #define IXGBE_SFF_SFF_8472_ESCB		0x76
@@ -48,6 +49,8 @@
 #define IXGBE_SFF_SOFT_RS_SELECT_10G	0x8
 #define IXGBE_SFF_SOFT_RS_SELECT_1G	0x0
 #define IXGBE_SFF_ADDRESSING_MODE	0x4
+#define IXGBE_SFF_DDM_IMPLEMENTED	0x40
+#define IXGBE_SFF_HAVE_RS		0x2
 #define IXGBE_SFF_QSFP_DA_ACTIVE_CABLE	0x1
 #define IXGBE_SFF_QSFP_DA_PASSIVE_CABLE	0x8
 #define IXGBE_SFF_QSFP_CONNECTOR_NOT_SEPARABLE	0x23
-- 
2.31.1