Messages in this thread Patches in this message | | | Date | Tue, 24 Sep 2013 23:38:44 +0200 | From | Sylwester Nawrocki <> | Subject | Re: [PATCH v6 0/5] clk: clock deregistration support |
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On 08/30/2013 04:53 PM, Sylwester Nawrocki wrote: > This patch series implements clock deregistration in the common clock > framework. Comparing to v5 it only includes further corrections of NULL > clock handling. [...] > clk: Provide not locked variant of of_clk_get_from_provider() > clkdev: Fix race condition in clock lookup from device tree > clk: Add common __clk_get(), __clk_put() implementations > clk: Assign module owner of a clock being registered > clk: Implement clk_unregister
Hi Mike, Russell,
Would you have any further comments/suggestions on this series ?
I have inspected all callers of clk_register() and all should be fine with regards to dereferencing dev->driver. The first argument to this function is either NULL or clk_register() is being called in drivers' probe() callback, which ensures dev->driver won't change due to holding dev->mutex.
The only issue I found might be at the omap3isp driver, which provides clock to its sub-drivers and takes reference on the sub-driver modules. When sub-driver calls clk_get() all modules would get locked in memory, due to circular reference. One solution to that could be to pass NULL struct device pointer, as in the below patch.
---------8<------------------ From ca5963041aad67e31324cb5d4d5e2cfce1706d4f Mon Sep 17 00:00:00 2001 From: Sylwester Nawrocki <s.nawrocki@samsung.com> Date: Thu, 19 Sep 2013 23:52:04 +0200 Subject: [PATCH] omap3isp: Pass NULL device pointer to clk_register()
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com> --- drivers/media/platform/omap3isp/isp.c | 15 ++++++++++----- drivers/media/platform/omap3isp/isp.h | 1 + 2 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/drivers/media/platform/omap3isp/isp.c b/drivers/media/platform/omap3isp/isp.c index df3a0ec..d7f3c98 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] = 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; @@ -306,9 +308,9 @@ static int isp_xclk_init(struct isp_device *isp)
xclk->hw.init = &init;
- clk = devm_clk_register(isp->dev, &xclk->hw); - if (IS_ERR(clk)) - return PTR_ERR(clk); + 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 +322,7 @@ 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 +337,9 @@ 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 cd3eff4..1498f2b 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 */ -- ---------8<------------------
Alternatively an additional argument could be added to the clk_register*() functions. Something like:
---------8<------------------ diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 27f8c42..ef934ac 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1837,7 +1837,8 @@ struct clk *__clk_register(struct device *dev, struct clk_hw *hw) } EXPORT_SYMBOL_GPL(__clk_register);
-static int _clk_register(struct device *dev, struct clk_hw *hw, struct clk *clk) +static int _clk_register(struct device *dev, struct clk_hw *hw, struct clk *clk, + struct module *owner) { int i, ret;
@@ -1877,6 +1878,8 @@ static int _clk_register(struct device *dev, struct clk_hw *hw, struct clk *clk) } }
+ clk->owner = owner; + ret = __clk_init(dev, clk); if (!ret) return 0; @@ -1892,7 +1895,7 @@ fail_name: }
/** - * clk_register - allocate a new clock, register it and return an opaque cookie + * ___clk_register - allocate a new clock, register it and return an opaque cookie * @dev: device that is registering this clock * @hw: link to hardware-specific clock data * @@ -1902,7 +1905,8 @@ fail_name: * rest of the clock API. In the event of an error clk_register will return an * error code; drivers must test for an error code after calling clk_register. */ -struct clk *clk_register(struct device *dev, struct clk_hw *hw) +struct clk *___clk_register(struct device *dev, struct clk_hw *hw, + struct module *owner) { int ret; struct clk *clk; @@ -1914,7 +1918,7 @@ struct clk *clk_register(struct device *dev, struct clk_hw *hw) goto fail_out; }
- ret = _clk_register(dev, hw, clk); + ret = _clk_register(dev, hw, clk, owner); if (!ret) return clk;
@@ -1922,7 +1926,7 @@ struct clk *clk_register(struct device *dev, struct clk_hw *hw) fail_out: return ERR_PTR(ret); } -EXPORT_SYMBOL_GPL(clk_register); +EXPORT_SYMBOL_GPL(___clk_register);
/* * Free memory allocated for a clock. @@ -2040,7 +2044,8 @@ static void devm_clk_release(struct device *dev, void *res) * automatically clk_unregister()ed on driver detach. See clk_register() for * more information. */ -struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw) +struct clk *__devm_clk_register(struct device *dev, struct clk_hw *hw, + struct module *owner) { struct clk *clk; int ret; @@ -2049,7 +2054,7 @@ struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw) if (!clk) return ERR_PTR(-ENOMEM);
- ret = _clk_register(dev, hw, clk); + ret = _clk_register(dev, hw, clk, owner); if (!ret) { devres_add(dev, clk); } else { @@ -2059,7 +2064,7 @@ struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw)
return clk; } -EXPORT_SYMBOL_GPL(devm_clk_register); +EXPORT_SYMBOL_GPL(__devm_clk_register);
static int devm_clk_match(struct device *dev, void *res, void *data) { diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index 13623f3..c656ebf 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -31,6 +31,7 @@ #define CLK_SET_RATE_NO_REPARENT BIT(7) /* don't re-parent on rate change */
struct clk_hw; +struct module;
/** * struct clk_ops - Callback operations for hardware clocks; these are to @@ -436,8 +437,21 @@ struct clk *clk_register_composite(struct device *dev, const char *name, * rest of the clock API. In the event of an error clk_register will return an * error code; drivers must test for an error code after calling clk_register. */ -struct clk *clk_register(struct device *dev, struct clk_hw *hw); -struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw); +struct clk *___clk_register(struct device *dev, struct clk_hw *hw, + struct module *owner); + +static inline struct clk *clk_register(struct device *dev, struct clk_hw *hw) +{ + return ___clk_register(dev, hw, THIS_MODULE); +} + +struct clk *__devm_clk_register(struct device *dev, struct clk_hw *hw, + struct module *owner); +static inline struct clk *devm_clk_register(struct device *dev, + struct clk_hw *hw) +{ + return __devm_clk_register(dev, hw, THIS_MODULE); +}
void clk_unregister(struct clk *clk); void devm_clk_unregister(struct device *dev, struct clk *clk); ---------8<------------------ Similarly it would need to be done for the remaining clk_register*() functions, which have much longer arguments list.
It's a bit messy, since there is already __clk_register() function with double underscore prefix. Perhaps that could be renamed to something else so all the functions taking struct module * parameter are prefixed with double underscore.
I would squash patches 3/5 and 4/5 in the next iteration, if it is decided to keep using dev->driver->owner.
-- Thanks, Sylwester
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