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

Javier Carrasco
2024-07-29T09:23:51Z

On 29/07/2024 10:23, Russell King (Oracle) wrote:
> 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" ?
>

I'll fix the typos for v3.

>> 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.
>

I will add your suggestions in a separate patch with the corresponding
Suggested-by: tag. In that case, and taking into account that the
pointer check is unnecessary, the loop after a goto err_port_probe will
turn into this:

err_port_probe:
for (i = 0; i < priv->port_count; i++)
mvpp2_port_remove(priv->port_list[i]);

and the loop in mvpp2_remove() will be exactly the one you suggested.

Apart from that, there is a suspicious check towards the end of the same
function:

if (is_acpi_node(port_fwnode))
return;

At the point it is called in the current implementation, port_fwnode
could have been cleaned. And after removing the loop, it is simply
uninitialized. Was that meant to be pdev->dev->fwnode?

Thanks and best regards,
Javier Carrasco