6.6-stable review patch. If anyone has any objections, please let me know.
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From: Rob Herring (Arm) robh@kernel.org
[ Upstream commit 805f7aaf7fee14a57b56af01d270edf6c10765e8 ]
It is possible for multiple, simultaneous callers calling device_node_get_regmap() with the same node to fail to find an entry in the syscon_list. There is a period of time while the first caller is calling of_syscon_register() that subsequent callers also fail to find an entry in the syscon_list and then call of_syscon_register() a second time.
Fix this by keeping the lock held until after of_syscon_register() completes and adds the node to syscon_list. Convert the spinlock to a mutex as many of the functions called in of_syscon_register() such as kzalloc() and of_clk_get() may sleep.
Fixes: bdb0066df96e ("mfd: syscon: Decouple syscon interface from platform devices") Signed-off-by: Rob Herring (Arm) robh@kernel.org Reviewed-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Tested-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Tested-by: Will McVicker willmcvicker@google.com Tested-by: Pankaj Dubey pankaj.dubey@samsung.com Reviewed-by: Pankaj Dubey pankaj.dubey@samsung.com Link: https://lore.kernel.org/r/20241217-syscon-fixes-v2-1-4f56d750541d@kernel.org Signed-off-by: Lee Jones lee@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/mfd/syscon.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c index 2ce15f60eb107..729e79e1be49f 100644 --- a/drivers/mfd/syscon.c +++ b/drivers/mfd/syscon.c @@ -15,6 +15,7 @@ #include <linux/io.h> #include <linux/init.h> #include <linux/list.h> +#include <linux/mutex.h> #include <linux/of.h> #include <linux/of_address.h> #include <linux/of_platform.h> @@ -27,7 +28,7 @@
static struct platform_driver syscon_driver;
-static DEFINE_SPINLOCK(syscon_list_slock); +static DEFINE_MUTEX(syscon_list_lock); static LIST_HEAD(syscon_list);
struct syscon { @@ -54,6 +55,8 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res) struct resource res; struct reset_control *reset;
+ WARN_ON(!mutex_is_locked(&syscon_list_lock)); + struct syscon *syscon __free(kfree) = kzalloc(sizeof(*syscon), GFP_KERNEL); if (!syscon) return ERR_PTR(-ENOMEM); @@ -144,9 +147,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res) syscon->regmap = regmap; syscon->np = np;
- spin_lock(&syscon_list_slock); list_add_tail(&syscon->list, &syscon_list); - spin_unlock(&syscon_list_slock);
return_ptr(syscon);
@@ -167,7 +168,7 @@ static struct regmap *device_node_get_regmap(struct device_node *np, { struct syscon *entry, *syscon = NULL;
- spin_lock(&syscon_list_slock); + mutex_lock(&syscon_list_lock);
list_for_each_entry(entry, &syscon_list, list) if (entry->np == np) { @@ -175,11 +176,11 @@ static struct regmap *device_node_get_regmap(struct device_node *np, break; }
- spin_unlock(&syscon_list_slock); - if (!syscon) syscon = of_syscon_register(np, check_res);
+ mutex_unlock(&syscon_list_lock); + if (IS_ERR(syscon)) return ERR_CAST(syscon);
@@ -210,7 +211,7 @@ int of_syscon_register_regmap(struct device_node *np, struct regmap *regmap) return -ENOMEM;
/* check if syscon entry already exists */ - spin_lock(&syscon_list_slock); + mutex_lock(&syscon_list_lock);
list_for_each_entry(entry, &syscon_list, list) if (entry->np == np) { @@ -223,12 +224,12 @@ int of_syscon_register_regmap(struct device_node *np, struct regmap *regmap)
/* register the regmap in syscon list */ list_add_tail(&syscon->list, &syscon_list); - spin_unlock(&syscon_list_slock); + mutex_unlock(&syscon_list_lock);
return 0;
err_unlock: - spin_unlock(&syscon_list_slock); + mutex_unlock(&syscon_list_lock); kfree(syscon); return ret; }