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    SubjectRe: [PATCH] remoteproc: Make rproc_get_by_phandle() work for clusters
    On Tue, Jan 03, 2023 at 11:48:56AM -0700, Mathieu Poirier wrote:
    > On Tue, 27 Dec 2022 at 08:11, Bjorn Andersson <andersson@kernel.org> wrote:
    > >
    > > 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?
    > >
    >
    > Platform device instances are created for the individual cores found
    > in the cluster, following the work done on TI's K3-R5[1].
    >

    Right, and this is a design pattern that I've been bitten by several
    times by now. There's no real purpose of spinning up platform_devices
    for those nodes.

    > > 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?
    > >
    >
    > That is exactly how things work for both K3-R5 and R5F architectures.
    > That said, if we use the cluster's platform device as parent of the
    > remote processors inside the cluster, function rproc_get_by_phandle()
    > will return the first remote processor it finds with a matching parent
    > rather than the remote processor referenced by the phandle parameter.
    >

    I missed the fact that we don't associate either the rproc or the rproc
    device with the of_node, but rather just rely on the fact that
    rproc->dev->parent->of_node is typically is the handle we're looking
    for.

    And I don't think we'll return the first instance, because
    rproc->dev->parent->of_node will never match the instance's of_node.


    I think it would be cleaner to add a of_node to struct rproc and use
    this for matching.

    And I do suggest that we don't of_platform_populate() in the TI driver.
    If nothing else, doing so saves ~2kb of wasted RAM...

    > [1]. https://elixir.bootlin.com/linux/v6.2-rc2/source/drivers/remoteproc/ti_k3_r5_remoteproc.c#L1728
    >
    > > Regards,
    > > Bjorn
    > >
    > > > Reported-by: Ben Levinsky <ben.levinsky@xilinx.com>
    > > > Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.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);

    Doing so also has the added benefit that we don't add an implicitly
    requirement on the rproc-device's parent being a platform_driver.

    Regards,
    Bjorn

    > > > + 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
    > > >

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