Re: [PATCH 6/6] net: mvpp2: use device_for_each_child_node() to access device child nodes

Russell King (Oracle)
2024-07-29T08:23:59Z

On Sat, Jul 06, 2024 at 05:23:38PM +0200, Javier Carrasco wrote:
> The iterated nodes are direct children of the device node, and the
> `device_for_each_child_node()` macro accounts for child node
> availability.
>
> `fwnode_for_each_available_child_node()` is meant to access the child
> nodes of an fwnode, and therefore not direct child nodes of the device
> node.
>
> The child nodes within mvpp2_probe are not accessed outside the lopps,

"lopps" ?

> and the socped version of the macro can be used to automatically

"socped" ?

> decrement the refcount on early exits.
>
> Use `device_for_each_child_node()` and its scoped variant to indicate
> device's direct child nodes.
>
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
> ---
> drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 13 ++++---------
> 1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index 9adf4301c9b1..97f1faab6f28 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -7417,8 +7417,6 @@ static int mvpp2_get_sram(struct platform_device *pdev,
>
> static int mvpp2_probe(struct platform_device *pdev)
> {
> - struct fwnode_handle *fwnode = pdev->dev.fwnode;
> - struct fwnode_handle *port_fwnode;
> struct mvpp2 *priv;
> struct resource *res;
> void __iomem *base;
> @@ -7591,7 +7589,7 @@ static int mvpp2_probe(struct platform_device *pdev)
> }
>
> /* Map DTS-active ports. Should be done before FIFO mvpp2_init */
> - fwnode_for_each_available_child_node(fwnode, port_fwnode) {
> + device_for_each_child_node_scoped(&pdev->dev, port_fwnode) {
> if (!fwnode_property_read_u32(port_fwnode, "port-id", &i))
> priv->port_map |= BIT(i);
> }
> @@ -7614,7 +7612,7 @@ static int mvpp2_probe(struct platform_device *pdev)
> goto err_axi_clk;
>
> /* Initialize ports */
> - fwnode_for_each_available_child_node(fwnode, port_fwnode) {
> + device_for_each_child_node_scoped(&pdev->dev, port_fwnode) {
> err = mvpp2_port_probe(pdev, port_fwnode, priv);
> if (err < 0)
> goto err_port_probe;
> @@ -7653,10 +7651,8 @@ static int mvpp2_probe(struct platform_device *pdev)
> return 0;
>
> err_port_probe:
> - fwnode_handle_put(port_fwnode);
> -
> i = 0;
> - fwnode_for_each_available_child_node(fwnode, port_fwnode) {
> + device_for_each_child_node_scoped(&pdev->dev, port_fwnode) {
> if (priv->port_list[i])
> mvpp2_port_remove(priv->port_list[i]);
> i++;
> @@ -7677,13 +7673,12 @@ static int mvpp2_probe(struct platform_device *pdev)
> static void mvpp2_remove(struct platform_device *pdev)
> {
> struct mvpp2 *priv = platform_get_drvdata(pdev);
> - struct fwnode_handle *fwnode = pdev->dev.fwnode;
> int i = 0, poolnum = MVPP2_BM_POOLS_NUM;
> struct fwnode_handle *port_fwnode;
>
> mvpp2_dbgfs_cleanup(priv);
>
> - fwnode_for_each_available_child_node(fwnode, port_fwnode) {
> + device_for_each_child_node(&pdev->dev, port_fwnode) {
> if (priv->port_list[i]) {
> mutex_destroy(&priv->port_list[i]->gather_stats_lock);
> mvpp2_port_remove(priv->port_list[i]);

This loop is just silly. There is no need to iterate the child nodes.
port_fwnode is not used, and the loop boils down to:

for (i = 0; i < priv->port_count; i++) {
mutex_destroy(&priv->port_list[i]->gather_stats_lock);
mvpp2_port_remove(priv->port_list[i]);
}

Not only is walking the child nodes not necessary, but checking whether
the pointer is NULL is also unnecessary. mvpp2_port_probe() populates
the array using:

priv->port_list[priv->port_count++] = port;

and "port" can not be NULL here, so we're guaranteed that all port_list
entries for 0..priv->port_count will be non-NULL, and the driver makes
this assumption in multiple places.

In fact, I'd say that using fwnode_for_each_available_child_node() or
device_for_each_child_node() is buggy here if the availability of the
children change - it could leave ports not cleaned up.

--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!