Re: [PATCH v2] bus: mhi: core: Check state before processing power_down

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Wed, Feb 17, 2021 at 09:43:31AM -0700, Jeffrey Hugo wrote:
> We cannot process a power_down if the power state is DISABLED.  There is
> no valid mhi_ctxt in that case, so attepting to process the power_down
> will likely result in a null pointer dereference.  If the power state is
> DISABLED, there is nothing to do anyways, so just bail early.
> 
> Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
> ---
> 
> v2: Fix subject and tweak the locking to avoid needless lock/unlock/relock
> 
>  drivers/bus/mhi/core/pm.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
> index 56ba3ab..47f6621 100644
> --- a/drivers/bus/mhi/core/pm.c
> +++ b/drivers/bus/mhi/core/pm.c
> @@ -1144,6 +1144,7 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
>  		mhi_deinit_dev_ctxt(mhi_cntrl);
>  
>  error_dev_ctxt:
> +	mhi_cntrl->pm_state = MHI_PM_DISABLE;
>  	mutex_unlock(&mhi_cntrl->pm_mutex);
>  
>  	return ret;
> @@ -1155,11 +1156,17 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
>  	enum mhi_pm_state cur_state, transition_state;
>  	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>  
> +	mutex_lock(&mhi_cntrl->pm_mutex);
> +	cur_state = mhi_cntrl->pm_state;

As I said in my previous review, you should use pm_lock for reading the
pm_state.

Thanks,
Mani

> +	if (cur_state == MHI_PM_DISABLE) {
> +		mutex_unlock(&mhi_cntrl->pm_mutex);
> +		return; /* Already powered down */
> +	}
> +
>  	/* If it's not a graceful shutdown, force MHI to linkdown state */
>  	transition_state = (graceful) ? MHI_PM_SHUTDOWN_PROCESS :
>  			   MHI_PM_LD_ERR_FATAL_DETECT;
>  
> -	mutex_lock(&mhi_cntrl->pm_mutex);
>  	write_lock_irq(&mhi_cntrl->pm_lock);
>  	cur_state = mhi_tryset_pm_state(mhi_cntrl, transition_state);
>  	if (cur_state != transition_state) {
> -- 
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>