linux-kernel - Re: [PATCH] remoteproc: Make rproc_get_by

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Date:   Tue, 27 Dec 2022 09:11:31 -0600
From:   Bjorn Andersson <andersson@...nel.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        ben.levinsky@...inx.com
Subject: Re: [PATCH] remoteproc: Make rproc_get_by_phandle() work for clusters

On Wed, Dec 14, 2022 at 03:16:43PM -0700, Mathieu Poirier wrote:
> Multi-cluster remoteproc designs typically have the following DT
> declaration:
> 
> 	remoteproc_cluster {
> 		compatible = "soc,remoteproc-cluster";
> 
>                 core0: core0 {
> 			compatible = "soc,remoteproc-core"
>                         memory-region;
>                         sram;
>                 };
> 
>                 core1: core1 {
> 			compatible = "soc,remoteproc-core"
>                         memory-region;
>                         sram;
>                 }
>         };
> 
> A driver exists for the cluster rather than the individual cores
> themselves so that operation mode and HW specific configurations
> applicable to the cluster can be made.
> 
> Because the driver exists at the cluster level and not the individual
> core level, function rproc_get_by_phandle() fails to return the
> remoteproc associated with the phandled it is called for.
> 
> This patch enhances rproc_get_by_phandle() by looking for the cluster's
> driver when the driver for the immediate remoteproc's parent is not
> found.
> 

Can you please help me understand why zynqmp_r5_remoteproc_probe()
invokes devm_of_platform_populate() to create platform_device instances
for the clusters?

Why can't the platform_device for the cluster be used as parent for both
remoteprocs and then the driver deal with the subnodes within the
driver?

Regards,
Bjorn

> Reported-by: Ben Levinsky <ben.levinsky@...inx.com>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---
>  drivers/remoteproc/remoteproc_core.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 1cd4815a6dd1..91f82886add9 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -33,6 +33,7 @@
>  #include <linux/idr.h>
>  #include <linux/elf.h>
>  #include <linux/crc32.h>
> +#include <linux/of_platform.h>
>  #include <linux/of_reserved_mem.h>
>  #include <linux/virtio_ids.h>
>  #include <linux/virtio_ring.h>
> @@ -2110,7 +2111,9 @@ EXPORT_SYMBOL(rproc_detach);
>  #ifdef CONFIG_OF
>  struct rproc *rproc_get_by_phandle(phandle phandle)
>  {
> +	struct platform_device *cluster_pdev;
>  	struct rproc *rproc = NULL, *r;
> +	struct device_driver *driver;
>  	struct device_node *np;
>  
>  	np = of_find_node_by_phandle(phandle);
> @@ -2121,7 +2124,30 @@ struct rproc *rproc_get_by_phandle(phandle phandle)
>  	list_for_each_entry_rcu(r, &rproc_list, node) {
>  		if (r->dev.parent && device_match_of_node(r->dev.parent, np)) {
>  			/* prevent underlying implementation from being removed */
> -			if (!try_module_get(r->dev.parent->driver->owner)) {
> +
> +			/*
> +			 * If the remoteproc's parent has a driver, the
> +			 * remoteproc is not part of a cluster and we can use
> +			 * that driver.
> +			 */
> +			driver = r->dev.parent->driver;
> +
> +			/*
> +			 * If the remoteproc's parent does not have a driver,
> +			 * look for the driver associated with the cluster.
> +			 */
> +			if (!driver) {
> +				cluster_pdev = of_find_device_by_node(np->parent);
> +				if (!cluster_pdev) {
> +					dev_err(&r->dev, "can't get parent\n");
> +					break;
> +				}
> +
> +				driver = cluster_pdev->dev.driver;
> +				put_device(&cluster_pdev->dev);
> +			}
> +
> +			if (!try_module_get(driver->owner)) {
>  				dev_err(&r->dev, "can't get owner\n");
>  				break;
>  			}
> -- 
> 2.25.1
>