[PATCH RESEND net-next] net: sfp: add debugfs support

[Russell King]

Add debugfs support to SFP so that the internal state of the SFP state
machines and hardware signal state can be viewed from userspace, rather
than having to compile a debug kernel to view state state transitions
in the kernel log.  The 'state' output looks like:

Module state: empty
Module probe attempts: 0 0
Device state: up
Main state: down
Fault recovery remaining retries: 5
PHY probe remaining retries: 12
moddef0: 0
rx_los: 1
tx_fault: 1
tx_disable: 1

Reviewed-by: Andrew Lunn <and...@lunn.ch>
Signed-off-by: Russell King <rmk+ker...@armlinux.org.uk>
---
 drivers/net/phy/sfp.c | 55 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 91d74c1a920a..374351de2063 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/acpi.h>
 #include <linux/ctype.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/hwmon.h>
@@ -258,6 +259,9 @@ struct sfp {
        char *hwmon_name;
 #endif
 
+#if IS_ENABLED(CONFIG_DEBUG_FS)
+       struct dentry *debugfs_dir;
+#endif
 };
 
 static bool sff_module_supported(const struct sfp_eeprom_id *id)
@@ -1390,6 +1394,54 @@ static void sfp_module_tx_enable(struct sfp *sfp)
        sfp_set_state(sfp, sfp->state);
 }
 
+#if IS_ENABLED(CONFIG_DEBUG_FS)
+static int sfp_debug_state_show(struct seq_file *s, void *data)
+{
+       struct sfp *sfp = s->private;
+
+       seq_printf(s, "Module state: %s\n",
+                  mod_state_to_str(sfp->sm_mod_state));
+       seq_printf(s, "Module probe attempts: %d %d\n",
+                  R_PROBE_RETRY_INIT - sfp->sm_mod_tries_init,
+                  R_PROBE_RETRY_SLOW - sfp->sm_mod_tries);
+       seq_printf(s, "Device state: %s\n",
+                  dev_state_to_str(sfp->sm_dev_state));
+       seq_printf(s, "Main state: %s\n",
+                  sm_state_to_str(sfp->sm_state));
+       seq_printf(s, "Fault recovery remaining retries: %d\n",
+                  sfp->sm_fault_retries);
+       seq_printf(s, "PHY probe remaining retries: %d\n",
+                  sfp->sm_phy_retries);
+       seq_printf(s, "moddef0: %d\n", !!(sfp->state & SFP_F_PRESENT));
+       seq_printf(s, "rx_los: %d\n", !!(sfp->state & SFP_F_LOS));
+       seq_printf(s, "tx_fault: %d\n", !!(sfp->state & SFP_F_TX_FAULT));
+       seq_printf(s, "tx_disable: %d\n", !!(sfp->state & SFP_F_TX_DISABLE));
+       return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(sfp_debug_state);
+
+static void sfp_debugfs_init(struct sfp *sfp)
+{
+       sfp->debugfs_dir = debugfs_create_dir(dev_name(sfp->dev), NULL);
+
+       debugfs_create_file("state", 0600, sfp->debugfs_dir, sfp,
+                           &sfp_debug_state_fops);
+}
+
+static void sfp_debugfs_exit(struct sfp *sfp)
+{
+       debugfs_remove_recursive(sfp->debugfs_dir);
+}
+#else
+static void sfp_debugfs_init(struct sfp *sfp)
+{
+}
+
+static void sfp_debugfs_exit(struct sfp *sfp)
+{
+}
+#endif
+
 static void sfp_module_tx_fault_reset(struct sfp *sfp)
 {
        unsigned int state = sfp->state;
@@ -2483,6 +2535,8 @@ static int sfp_probe(struct platform_device *pdev)
        if (!sfp->sfp_bus)
                return -ENOMEM;
 
+       sfp_debugfs_init(sfp);
+
        return 0;
 }
 
@@ -2490,6 +2544,7 @@ static int sfp_remove(struct platform_device *pdev)
 {
        struct sfp *sfp = platform_get_drvdata(pdev);
 
+       sfp_debugfs_exit(sfp);
        sfp_unregister_socket(sfp->sfp_bus);
 
        rtnl_lock();
-- 
2.20.1