Re: [PATCH] remoteproc: qcom: wcnss: Add iris completion barrier

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Wed, Feb 12, 2020 at 06:54:03PM +0100, Loic Poulain wrote:
> There is no guarantee that the iris pointer will be assigned before
> remoteproc subsystem starts the wcnss rproc, actually it depends how
> fast rproc subsystem is able to get the firmware to trigger the start.
> 
> This leads to sporadic wifi/bluetooth initialization issue on db410c
> with the following output:
>  remoteproc remoteproc1: powering up a204000.wcnss
>  remoteproc remoteproc1: Booting fw image qcom/msm8916/wcnss.mdt...
>  qcom-wcnss-pil a204000.wcnss: no iris registered
>  remoteproc remoteproc1: can't start rproc a204000.wcnss: -22
> 
> This patch introduces a 'iris_assigned' completion barrier to fix
> this issue. Maybe not the most elegant way, but it does the trick.
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> ---
>  drivers/remoteproc/qcom_wcnss.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/remoteproc/qcom_wcnss.c b/drivers/remoteproc/qcom_wcnss.c
> index a0468b3..c888282 100644
> --- a/drivers/remoteproc/qcom_wcnss.c
> +++ b/drivers/remoteproc/qcom_wcnss.c
> @@ -84,6 +84,7 @@ struct qcom_wcnss {
>  
>  	struct completion start_done;
>  	struct completion stop_done;
> +	struct completion iris_assigned;
>  
>  	phys_addr_t mem_phys;
>  	phys_addr_t mem_reloc;
> @@ -138,6 +139,7 @@ void qcom_wcnss_assign_iris(struct qcom_wcnss *wcnss,
>  
>  	wcnss->iris = iris;
>  	wcnss->use_48mhz_xo = use_48mhz_xo;
> +	complete(&wcnss->iris_assigned);
>  
>  	mutex_unlock(&wcnss->iris_lock);
>  }
> @@ -213,6 +215,10 @@ static int wcnss_start(struct rproc *rproc)
>  	struct qcom_wcnss *wcnss = (struct qcom_wcnss *)rproc->priv;
>  	int ret;
>  
> +	/* Grant some time for iris registration */
> +	wait_for_completion_timeout(&wcnss->iris_assigned,
> +				    msecs_to_jiffies(5000));
> +
>  	mutex_lock(&wcnss->iris_lock);
>  	if (!wcnss->iris) {
>  		dev_err(wcnss->dev, "no iris registered\n");
> @@ -494,6 +500,7 @@ static int wcnss_probe(struct platform_device *pdev)
>  
>  	init_completion(&wcnss->start_done);
>  	init_completion(&wcnss->stop_done);
> +	init_completion(&wcnss->iris_assigned);
>  
>  	mutex_init(&wcnss->iris_lock);

If I understand the problem correctly, if loading the fw image takes long enough,
qcom_iris_probe() that is triggered by of_platform_populate() has time to
complete and call qcom_wcnss_assign_iris().  Otherwise the remoteproc core calls
wcnss_start() before qcom_wcnss_assign_iris() had the opportunity to run.

If I am correct, would it be possible to call of_platform_populate() before
calling rproc_add()?  There might be some refactoring to do but that's probably
better than introducing a delay...

Thanks,
Mathieu

>  
> -- 
> 2.7.4
>