omap3isp: Modify clocks registration to avoid circular references

The clock core code is going to be modified so clk_get() takes
reference on the clock provider module. Until the potential circular
reference issue is properly addressed, we pass NULL as the first
argument to clk_register(), in order to disallow sub-devices taking
a reference on the ISP module back trough clk_get(). This should
prevent locking the modules in memory.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

2 files changed, 17 insertions, 6 deletions

diff --git a/drivers/media/platform/omap3isp/isp.c b/drivers/media/platform/omap3isp/isp.c
index 1c3608039663..59106623e71e 100644
--- a/drivers/media/platform/omap3isp/isp.c
+++ b/drivers/media/platform/omap3isp/isp.c
@@ -290,9 +290,11 @@ static int isp_xclk_init(struct isp_device *isp)
         struct clk_init_data init;
         unsigned int i;
 
+        for (i = 0; i < ARRAY_SIZE(isp->xclks); ++i)
+                isp->xclks[i].clk = ERR_PTR(-EINVAL);
+
         for (i = 0; i < ARRAY_SIZE(isp->xclks); ++i) {
                 struct isp_xclk *xclk = &isp->xclks[i];
-                struct clk *clk;
 
                 xclk->isp = isp;
                 xclk->id = i == 0 ? ISP_XCLK_A : ISP_XCLK_B;
@@ -305,10 +307,15 @@ static int isp_xclk_init(struct isp_device *isp)
                 init.num_parents = 1;
 
                 xclk->hw.init = &init;
-
-                clk = devm_clk_register(isp->dev, &xclk->hw);
-                if (IS_ERR(clk))
-                        return PTR_ERR(clk);
+                /*
+                 * The first argument is NULL in order to avoid circular
+                 * reference, as this driver takes reference on the
+                 * sensor subdevice modules and the sensors would take
+                 * reference on this module through clk_get().
+                 */
+                xclk->clk = clk_register(NULL, &xclk->hw);
+                if (IS_ERR(xclk->clk))
+                        return PTR_ERR(xclk->clk);
 
                 if (pdata->xclks[i].con_id == NULL &&
                     pdata->xclks[i].dev_id == NULL)
@@ -320,7 +327,7 @@ static int isp_xclk_init(struct isp_device *isp)
 
                 xclk->lookup->con_id = pdata->xclks[i].con_id;
                 xclk->lookup->dev_id = pdata->xclks[i].dev_id;
-                xclk->lookup->clk = clk;
+                xclk->lookup->clk = xclk->clk;
 
                 clkdev_add(xclk->lookup);
         }
@@ -335,6 +342,9 @@ static void isp_xclk_cleanup(struct isp_device *isp)
         for (i = 0; i < ARRAY_SIZE(isp->xclks); ++i) {
                 struct isp_xclk *xclk = &isp->xclks[i];
 
+                if (!IS_ERR(xclk->clk))
+                        clk_unregister(xclk->clk);
+
                 if (xclk->lookup)
                         clkdev_drop(xclk->lookup);
         }
diff --git a/drivers/media/platform/omap3isp/isp.h b/drivers/media/platform/omap3isp/isp.h
index ce65d3ae1aa7..d1e857e41731 100644
--- a/drivers/media/platform/omap3isp/isp.h
+++ b/drivers/media/platform/omap3isp/isp.h
@@ -135,6 +135,7 @@ struct isp_xclk {
         struct isp_device *isp;
         struct clk_hw hw;
         struct clk_lookup *lookup;
+        struct clk *clk;
         enum isp_xclk_id id;
 
         spinlock_t lock;        /* Protects enabled and divider */