6.8-stable review patch. If anyone has any objections, please let me know.
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From: Marek Vasut marex@denx.de
[ Upstream commit c819d7b836c5dfca0854d3e56664293601f2176d ]
The clock management in this driver does not seem to be correct. The struct hwrng .init callback enables the clock, but there is no matching .cleanup callback to disable the clock. The clock get disabled as some later point by runtime PM suspend callback.
Furthermore, both runtime PM and sleep suspend callbacks access registers first and disable clock which are used for register access second. If the IP is already in RPM suspend and the system enters sleep state, the sleep callback will attempt to access registers while the register clock are already disabled. This bug has been fixed once before already in commit 9bae54942b13 ("hwrng: stm32 - fix pm_suspend issue"), and regressed in commit ff4e46104f2e ("hwrng: stm32 - rework power management sequences") .
Fix this slightly differently, disable register clock at the end of .init callback, this way the IP is disabled after .init. On every access to the IP, which really is only stm32_rng_read(), do pm_runtime_get_sync() which is already done in stm32_rng_read() to bring the IP from RPM suspend, and pm_runtime_mark_last_busy()/pm_runtime_put_sync_autosuspend() to put it back into RPM suspend.
Change sleep suspend/resume callbacks to enable and disable register clock around register access, as those cannot use the RPM suspend/resume callbacks due to slightly different initialization in those sleep callbacks. This way, the register access should always be performed with clock surely enabled.
Fixes: ff4e46104f2e ("hwrng: stm32 - rework power management sequences") Signed-off-by: Marek Vasut marex@denx.de Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/char/hw_random/stm32-rng.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c index b6182f86d8a4b..0e903d6e22e30 100644 --- a/drivers/char/hw_random/stm32-rng.c +++ b/drivers/char/hw_random/stm32-rng.c @@ -363,6 +363,8 @@ static int stm32_rng_init(struct hwrng *rng) return -EINVAL; }
+ clk_disable_unprepare(priv->clk); + return 0; }
@@ -387,6 +389,11 @@ static int __maybe_unused stm32_rng_runtime_suspend(struct device *dev) static int __maybe_unused stm32_rng_suspend(struct device *dev) { struct stm32_rng_private *priv = dev_get_drvdata(dev); + int err; + + err = clk_prepare_enable(priv->clk); + if (err) + return err;
if (priv->data->has_cond_reset) { priv->pm_conf.nscr = readl_relaxed(priv->base + RNG_NSCR); @@ -468,6 +475,8 @@ static int __maybe_unused stm32_rng_resume(struct device *dev) writel_relaxed(reg, priv->base + RNG_CR); }
+ clk_disable_unprepare(priv->clk); + return 0; }