[PATCH v2] gpio: mvebu: fix NULL pointer dereference in suspend/resume

[Yun Zhou]

mvebu_pwm_suspend() and mvebu_pwm_resume() are called for all GPIO
banks during suspend/resume, but not all banks have PWM functionality.
GPIO banks without PWM have mvchip->mvpwm set to NULL.

Calling mvebu_pwm_suspend() with mvpwm == NULL causes a NULL pointer
dereference when it tries to access mvpwm->blink_select.

  Unable to handle kernel NULL pointer dereference at virtual address 00000020 when write
  [00000020] *pgd=00000000
  Internal error: Oops: 815 [#1] PREEMPT ARM
  Modules linked in:
  CPU: 0 UID: 0 PID: 406 Comm: sh Not tainted 6.12.74-rt12-yocto-standard-g4e96f98fb7db-dirty #353
  Hardware name: Marvell Armada 370/XP (Device Tree)
  PC is at regmap_mmio_read+0x38/0x54
  LR is at regmap_mmio_read+0x38/0x54
  pc : [<c05fd2ac>]    lr : [<c05fd2ac>]    psr: 200f0013
  sp : f0c11d10  ip : 00000000  fp : c100d2f0
  r10: c14fb854  r9 : 00000000  r8 : 00000000
  r7 : c1799c00  r6 : 00000020  r5 : 00000020  r4 : c179c7c0
  r3 : f0a231a0  r2 : 00000020  r1 : 00000020  r0 : 00000000
  Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
  Control: 10c5387d  Table: 135ec059  DAC: 00000051
  Call trace:
   regmap_mmio_read from _regmap_bus_reg_read+0x78/0xac
   _regmap_bus_reg_read from _regmap_read+0x60/0x154
   _regmap_read from regmap_read+0x3c/0x60
   regmap_read from mvebu_gpio_suspend+0xa4/0x14c
   mvebu_gpio_suspend from dpm_run_callback+0x54/0x180
   dpm_run_callback from device_suspend+0x124/0x630
   device_suspend from dpm_suspend+0x124/0x270
   dpm_suspend from dpm_suspend_start+0x64/0x6c
   dpm_suspend_start from suspend_devices_and_enter+0x140/0x8e8
   suspend_devices_and_enter from pm_suspend+0x2fc/0x308
   pm_suspend from state_store+0x6c/0xc8
   state_store from kernfs_fop_write_iter+0x10c/0x1f8
   kernfs_fop_write_iter from vfs_write+0x270/0x468
   vfs_write from ksys_write+0x70/0xf0
   ksys_write from ret_fast_syscall+0x0/0x54

Add a NULL check for mvchip->mvpwm before calling the PWM
suspend/resume functions.

Fixes: 757642f9a584 ("gpio: mvebu: Add limited PWM support")
Signed-off-by: Yun Zhou <yun.zhou@xxxxxxxxxxxxx>
---
v2:
 - Fix Fixes tag commit title

 drivers/gpio/gpio-mvebu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
index 22c36b79e249..c030d1f00abc 100644
--- a/drivers/gpio/gpio-mvebu.c
+++ b/drivers/gpio/gpio-mvebu.c
@@ -996,7 +996,7 @@ static int mvebu_gpio_suspend(struct platform_device *pdev, pm_message_t state)
 		BUG();
 	}
 
-	if (IS_REACHABLE(CONFIG_PWM))
+	if (IS_REACHABLE(CONFIG_PWM) && mvchip->mvpwm)
 		mvebu_pwm_suspend(mvchip);
 
 	return 0;
@@ -1048,7 +1048,7 @@ static int mvebu_gpio_resume(struct platform_device *pdev)
 		BUG();
 	}
 
-	if (IS_REACHABLE(CONFIG_PWM))
+	if (IS_REACHABLE(CONFIG_PWM) && mvchip->mvpwm)
 		mvebu_pwm_resume(mvchip);
 
 	return 0;
-- 
2.43.0