media: staging: media: atomisp: Fix oops by unbalanced clk enable/disable call

The common-clk core expects clk consumers to always call enable/disable
in a balanced manner. The atomisp driver does not call gmin_flisclk_ctrl()
in a balanced manner, so add a clock_on bool and skip redundant calls.

This fixes kernel oops like this one:

[   19.811613] gc0310_s_config S
[   19.811655] ------------[ cut here ]------------
[   19.811664] WARNING: CPU: 1 PID: 720 at drivers/clk/clk.c:594 clk_core_disabl
[   19.811666] Modules linked in: tpm_crb(+) snd_soc_sst_atom_hifi2_platform tpm
[   19.811744] CPU: 1 PID: 720 Comm: systemd-udevd Tainted: G         C OE   4.1
[   19.811746] Hardware name: Insyde T701/T701, BIOS BYT70A.YNCHENG.WIN.007 08/2
[   19.811749] task: ffff988df7ab2500 task.stack: ffffac1400474000
[   19.811752] RIP: 0010:clk_core_disable+0xc0/0x130
...
[   19.811775] Call Trace:
[   19.811783]  clk_core_disable_lock+0x1f/0x30
[   19.811788]  clk_disable+0x1f/0x30
[   19.811794]  gmin_flisclk_ctrl+0x87/0xf0
[   19.811801]  0xffffffffc0528512
[   19.811805]  0xffffffffc05295e2
[   19.811811]  ? acpi_device_wakeup_disable+0x50/0x60
[   19.811815]  ? acpi_dev_pm_attach+0x8e/0xd0
[   19.811818]  ? 0xffffffffc05294d0
[   19.811823]  i2c_device_probe+0x1cd/0x280
[   19.811828]  driver_probe_device+0x2ff/0x450

Fixes: "staging: atomisp: use clock framework for camera clocks"
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/staging/media/atomisp/platform/intel-mid/atomisp_gmin_platform.c

@@ -29,6 +29,7 @@ struct gmin_subdev {
 	struct v4l2_subdev *subdev;
 	int clock_num;
 	int clock_src;
+	bool clock_on;
 	struct clk *pmc_clk;
 	struct gpio_desc *gpio0;
 	struct gpio_desc *gpio1;
@@ -572,6 +573,9 @@ static int gmin_flisclk_ctrl(struct v4l2_subdev *subdev, int on)
 	struct gmin_subdev *gs = find_gmin_subdev(subdev);
 	struct i2c_client *client = v4l2_get_subdevdata(subdev);
 
+	if (gs->clock_on == !!on)
+		return 0;
+
 	if (on) {
 		ret = clk_set_rate(gs->pmc_clk, gs->clock_src);
 
@@ -580,8 +584,11 @@ static int gmin_flisclk_ctrl(struct v4l2_subdev *subdev, int on)
 				gs->clock_src);
 
 		ret = clk_prepare_enable(gs->pmc_clk);
+		if (ret == 0)
+			gs->clock_on = true;
 	} else {
 		clk_disable_unprepare(gs->pmc_clk);
+		gs->clock_on = false;
 	}
 
 	return ret;