Re: [PATCH v4 1/3] misc: fastrpc: iterate CB nodes manually instead of of_platform_populate

[Ekansh Gupta]

On 26-08-2026 18:55, Vinayak Katoch wrote:
> of_platform_populate() only guarantees that child devices are registered,
> not that their probes have completed before it returns. This creates a
> window where fastrpc_cb_init() may not have run for all context bank
> nodes, leaving the channel context partially initialised.
> 
> Iterate over the child device tree nodes directly, initialising each
> qcom,fastrpc-compute-cb device synchronously. This ensures all context
> banks are fully initialised before fastrpc_rpmsg_probe() returns. Since
> fastrpc_cb_driver is no longer needed as an independent platform driver,
> remove it along with its match table and remove callback. Set
> OF_POPULATED_BUS on the rpmsg node so that of_platform_depopulate()
> correctly removes the manually created CB devices on teardown.
> 
> Signed-off-by: Vinayak Katoch <vinayak.katoch@xxxxxxxxxxxxxxxx>
> ---
>  drivers/misc/fastrpc.c | 83 ++++++++++++++++++--------------------------------
>  1 file changed, 29 insertions(+), 54 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index d4fac2caca86..a153107d0085 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -2363,7 +2363,7 @@ static const struct file_operations fastrpc_fops = {
>  	.compat_ioctl = fastrpc_device_ioctl,
>  };
>  
> -static int fastrpc_cb_probe(struct platform_device *pdev)
> +static int fastrpc_cb_init(struct platform_device *pdev)
>  {
>  	struct fastrpc_channel_ctx *cctx;
>  	struct fastrpc_session_ctx *sess;
> @@ -2385,7 +2385,7 @@ static int fastrpc_cb_probe(struct platform_device *pdev)
>  	spin_lock_irqsave(&cctx->lock, flags);
>  	if (cctx->sesscount >= FASTRPC_MAX_SESSIONS) {
>  		spin_unlock_irqrestore(&cctx->lock, flags);
> -		dev_err(&pdev->dev, "too many sessions\n");
> +		dev_err(dev, "too many sessions\n");
>  		return -ENOSPC;
>  	}
>  	dma_bits = cctx->soc_data->dma_addr_bits_default;
> @@ -2419,38 +2419,6 @@ static int fastrpc_cb_probe(struct platform_device *pdev)
>  	return 0;
>  }
>  
> -static void fastrpc_cb_remove(struct platform_device *pdev)
> -{
> -	struct fastrpc_channel_ctx *cctx = dev_get_drvdata(pdev->dev.parent);
> -	struct fastrpc_session_ctx *sess = dev_get_drvdata(&pdev->dev);
> -	unsigned long flags;
> -	int i;
> -
> -	spin_lock_irqsave(&cctx->lock, flags);
> -	for (i = 0; i < FASTRPC_MAX_SESSIONS; i++) {
> -		if (cctx->session[i].sid == sess->sid) {
> -			cctx->session[i].valid = false;
> -			cctx->sesscount--;
> -		}
> -	}
> -	spin_unlock_irqrestore(&cctx->lock, flags);
> -}
> -
> -static const struct of_device_id fastrpc_match_table[] = {
> -	{ .compatible = "qcom,fastrpc-compute-cb" },
> -	{ }
> -};
> -
> -static struct platform_driver fastrpc_cb_driver = {
> -	.probe = fastrpc_cb_probe,
> -	.remove = fastrpc_cb_remove,
> -	.driver = {
> -		.name = "qcom,fastrpc-cb",
> -		.of_match_table = fastrpc_match_table,
> -		.suppress_bind_attrs = true,
> -	},
> -};
> -
>  static int fastrpc_device_register(struct device *dev, struct fastrpc_channel_ctx *cctx,
>  				   bool is_secured, const char *domain)
>  {
> @@ -2642,12 +2610,29 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
>  	data->rpdev = rpdev;
>  	dev_set_drvdata(&rpdev->dev, data);
>  
> -	err = of_platform_populate(rdev->of_node, NULL, NULL, rdev);
> -	if (err)
> -		goto err_deregister_fdev;
> +	of_node_set_flag(rdev->of_node, OF_POPULATED_BUS);
> +
> +	for_each_available_child_of_node_scoped(rdev->of_node, np) {
> +		struct platform_device *pdev;
> +
> +		if (!of_device_is_compatible(np, "qcom,fastrpc-compute-cb"))
> +			continue;
> +
> +		pdev = of_platform_device_create(np, NULL, rdev);
> +		if (!pdev) {
> +			err = -EINVAL;
> +			goto err_depopulate;
> +		}
> +
> +		err = fastrpc_cb_init(pdev);
> +		if (err)
> +			goto err_depopulate;
> +	}
>  
>  	return 0;
>  
> +err_depopulate:
> +	of_platform_depopulate(rdev);
>  err_deregister_fdev:
>  	if (data->fdevice)
>  		misc_deregister(&data->fdevice->miscdev);
> @@ -2677,6 +2662,7 @@ static void fastrpc_rpmsg_remove(struct rpmsg_device *rpdev)
>  	struct fastrpc_buf *buf, *b;
>  	struct fastrpc_user *user;
>  	unsigned long flags;
> +	int i;
>  
>  	/* No invocations past this point */
>  	spin_lock_irqsave(&cctx->lock, flags);
> @@ -2697,6 +2683,11 @@ static void fastrpc_rpmsg_remove(struct rpmsg_device *rpdev)
>  	if (cctx->remote_heap)
>  		fastrpc_buf_free(cctx->remote_heap);
>  
> +	spin_lock_irqsave(&cctx->lock, flags);
> +	for (i = 0; i < FASTRPC_MAX_SESSIONS; i++)
> +		cctx->session[i].valid = false;
> +	spin_unlock_irqrestore(&cctx->lock, flags);
> +
>  	of_platform_depopulate(&rpdev->dev);
should this also be removed?>
>  	fastrpc_channel_ctx_put(cctx);
> @@ -2786,28 +2777,12 @@ static struct rpmsg_driver fastrpc_driver = {
>  
>  static int fastrpc_init(void)
>  {
> -	int ret;
> -
> -	ret = platform_driver_register(&fastrpc_cb_driver);
> -	if (ret < 0) {
> -		pr_err("fastrpc: failed to register cb driver\n");
> -		return ret;
> -	}
> -
> -	ret = register_rpmsg_driver(&fastrpc_driver);
> -	if (ret < 0) {
> -		pr_err("fastrpc: failed to register rpmsg driver\n");
> -		platform_driver_unregister(&fastrpc_cb_driver);
> -		return ret;
> -	}
> -
> -	return 0;
> +	return register_rpmsg_driver(&fastrpc_driver);
>  }
>  module_init(fastrpc_init);
can you use module_rpmsg_driver() instead?>
>  static void fastrpc_exit(void)
>  {
> -	platform_driver_unregister(&fastrpc_cb_driver);
>  	unregister_rpmsg_driver(&fastrpc_driver);
>  }
>  module_exit(fastrpc_exit);
>