[PATCH v3 net] net: mscc: ocelot: unregister the PTP clock on deinit

[Vladimir Oltean <olteanv@gmail.com>]

From: Vladimir Oltean <vladimir.oltean@nxp.com>

Currently a switch driver deinit frees the regmaps, but the PTP clock is
still out there, available to user space via /dev/ptpN. Any PTP
operation is a ticking time bomb, since it will attempt to use the freed
regmaps and thus trigger kernel panics:

[    4.291746] fsl_enetc 0000:00:00.2 eth1: error -22 setting up slave phy
[    4.291871] mscc_felix 0000:00:00.5: Failed to register DSA switch: -22
[    4.308666] mscc_felix: probe of 0000:00:00.5 failed with error -22
[    6.358270] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000088
[    6.367090] Mem abort info:
[    6.369888]   ESR = 0x96000046
[    6.369891]   EC = 0x25: DABT (current EL), IL = 32 bits
[    6.369892]   SET = 0, FnV = 0
[    6.369894]   EA = 0, S1PTW = 0
[    6.369895] Data abort info:
[    6.369897]   ISV = 0, ISS = 0x00000046
[    6.369899]   CM = 0, WnR = 1
[    6.369902] user pgtable: 4k pages, 48-bit VAs, pgdp=00000020d58c7000
[    6.369904] [0000000000000088] pgd=00000020d5912003, pud=00000020d5915003, pmd=0000000000000000
[    6.369914] Internal error: Oops: 96000046 [#1] PREEMPT SMP
[    6.420443] Modules linked in:
[    6.423506] CPU: 1 PID: 262 Comm: phc_ctl Not tainted 5.4.0-03625-gb7b2a5dadd7f #204
[    6.431273] Hardware name: LS1028A RDB Board (DT)
[    6.435989] pstate: 40000085 (nZcv daIf -PAN -UAO)
[    6.440802] pc : css_release+0x24/0x58
[    6.444561] lr : regmap_read+0x40/0x78
[    6.448316] sp : ffff800010513cc0
[    6.451636] x29: ffff800010513cc0 x28: ffff002055873040
[    6.456963] x27: 0000000000000000 x26: 0000000000000000
[    6.462289] x25: 0000000000000000 x24: 0000000000000000
[    6.467617] x23: 0000000000000000 x22: 0000000000000080
[    6.472944] x21: ffff800010513d44 x20: 0000000000000080
[    6.478270] x19: 0000000000000000 x18: 0000000000000000
[    6.483596] x17: 0000000000000000 x16: 0000000000000000
[    6.488921] x15: 0000000000000000 x14: 0000000000000000
[    6.494247] x13: 0000000000000000 x12: 0000000000000000
[    6.499573] x11: 0000000000000000 x10: 0000000000000000
[    6.504899] x9 : 0000000000000000 x8 : 0000000000000000
[    6.510225] x7 : 0000000000000000 x6 : ffff800010513cf0
[    6.515550] x5 : 0000000000000000 x4 : 0000000fffffffe0
[    6.520876] x3 : 0000000000000088 x2 : ffff800010513d44
[    6.526202] x1 : ffffcada668ea000 x0 : ffffcada64d8b0c0
[    6.531528] Call trace:
[    6.533977]  css_release+0x24/0x58
[    6.537385]  regmap_read+0x40/0x78
[    6.540795]  __ocelot_read_ix+0x6c/0xa0
[    6.544641]  ocelot_ptp_gettime64+0x4c/0x110
[    6.548921]  ptp_clock_gettime+0x4c/0x58
[    6.552853]  pc_clock_gettime+0x5c/0xa8
[    6.556699]  __arm64_sys_clock_gettime+0x68/0xc8
[    6.561331]  el0_svc_common.constprop.2+0x7c/0x178
[    6.566133]  el0_svc_handler+0x34/0xa0
[    6.569891]  el0_sync_handler+0x114/0x1d0
[    6.573908]  el0_sync+0x140/0x180
[    6.577232] Code: d503201f b00119a1 91022263 b27b7be4 (f9004663)
[    6.583349] ---[ end trace d196b9b14cdae2da ]---
[    6.587977] Kernel panic - not syncing: Fatal exception
[    6.593216] SMP: stopping secondary CPUs
[    6.597151] Kernel Offset: 0x4ada54400000 from 0xffff800010000000
[    6.603261] PHYS_OFFSET: 0xffffd0a7c0000000
[    6.607454] CPU features: 0x10002,21806008
[    6.611558] Memory Limit: none

And now that ocelot->ptp_clock is checked at exit, prevent a potential
error where ptp_clock_register returned a pointer-encoded error, which
we are keeping in the ocelot private data structure. So now,
ocelot->ptp_clock is now either NULL or a valid pointer.

Fixes: 4e3b0468e6d7 ("net: mscc: PTP Hardware Clock (PHC) support")
Cc: Antoine Tenart <antoine.tenart@bootlin.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
Changes in v3:
- Unregistered the PTP clock inline instead of calling a separate
  function (ocelot_deinit_timestamp).

Changes in v2:
- Dropped the redundant check on ocelot->ptp and changed the topic of
  the if condition.
- Populated ocelot->ptp_clock in ocelot_init_timestamp only on valid
  return value from ptp_clock_register, so that the deinit check can
  never mis-trigger.

 drivers/net/ethernet/mscc/ocelot.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index ff491510e5b2..658a86867419 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -2165,14 +2165,18 @@ static struct ptp_clock_info ocelot_ptp_clock_info = {
 
 static int ocelot_init_timestamp(struct ocelot *ocelot)
 {
+	struct ptp_clock *ptp_clock;
+
 	ocelot->ptp_info = ocelot_ptp_clock_info;
-	ocelot->ptp_clock = ptp_clock_register(&ocelot->ptp_info, ocelot->dev);
-	if (IS_ERR(ocelot->ptp_clock))
-		return PTR_ERR(ocelot->ptp_clock);
+	ptp_clock = ptp_clock_register(&ocelot->ptp_info, ocelot->dev);
+	if (IS_ERR(ptp_clock))
+		return PTR_ERR(ptp_clock);
 	/* Check if PHC support is missing at the configuration level */
-	if (!ocelot->ptp_clock)
+	if (!ptp_clock)
 		return 0;
 
+	ocelot->ptp_clock = ptp_clock;
+
 	ocelot_write(ocelot, SYS_PTP_CFG_PTP_STAMP_WID(30), SYS_PTP_CFG);
 	ocelot_write(ocelot, 0xffffffff, ANA_TABLES_PTP_ID_LOW);
 	ocelot_write(ocelot, 0xffffffff, ANA_TABLES_PTP_ID_HIGH);
@@ -2503,6 +2507,8 @@ void ocelot_deinit(struct ocelot *ocelot)
 	destroy_workqueue(ocelot->stats_queue);
 	mutex_destroy(&ocelot->stats_lock);
 	ocelot_ace_deinit();
+	if (ocelot->ptp_clock)
+		ptp_clock_unregister(ocelot->ptp_clock);
 
 	for (i = 0; i < ocelot->num_phys_ports; i++) {
 		port = ocelot->ports[i];
-- 
2.17.1