Re: [PATCH 1/2] clk: Do not register provider with a NULL dev->of_node

[<Tudor.Ambarus@microchip.com>]

On 4/23/21 9:21 PM, nicolas saenz julienne wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Hi Saravana, Tudor,
> 
> On Fri, 2021-04-23 at 10:24 -0700, Saravana Kannan wrote:
>> On Fri, Apr 23, 2021 at 10:14 AM Tudor Ambarus
>> <tudor.ambarus@microchip.com> wrote:
>>>
>>> commit 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
>>> revealed that clk/bcm/clk-raspberrypi.c driver calls
>>> devm_of_clk_add_hw_provider(), with a NULL dev->of_node.
>>>
>>> devm_of_clk_add_hw_provider() should not register the provider with
>>> a NULL dev->of_node, as there is no of_node. Apart of the NULL pointer
>>> dereference that will result when calling fwnode_dev_initialized() in
>>> of_clk_add_hw_provider(), another problem is that when two drivers calling
>>> of_clk_add_hw_provider() with np = NULL, their unregistration order is not
>>> guaranteed to be correct. Avoid all the problems and just return -ENODEV
>>> when the callers of devm_of_clk_add_hw_provider() use a NULL dev->of_node,
>>> which seems the natural way to do.
>>>
>>> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> Fixes: 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
>>> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
>>> ---
>>>  drivers/clk/clk.c | 12 +++++++-----
>>>  1 file changed, 7 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>>> index e2ec1b745243..8b5077cc5e67 100644
>>> --- a/drivers/clk/clk.c
>>> +++ b/drivers/clk/clk.c
>>> @@ -4634,11 +4634,10 @@ static struct device_node *get_clk_provider_node(struct device *dev)
>>>   * @get: callback for decoding clk_hw
>>>   * @data: context pointer for @get callback
>>>   *
>>> - * Registers clock provider for given device's node. If the device has no DT
>>> - * node or if the device node lacks of clock provider information (#clock-cells)
>>> - * then the parent device's node is scanned for this information. If parent node
>>> - * has the #clock-cells then it is used in registration. Provider is
>>> - * automatically released at device exit.
>>> + * Registers clock provider for given device's node. If the device node lacks
>>> + * of clock provider information (#clock-cells) then the parent device's node is
>>> + * scanned for this information. If parent node has the #clock-cells then it is
>>> + * used in registration. Provider is automatically released at device exit.
>>>   *
>>>   * Return: 0 on success or an errno on failure.
>>>   */
>>> @@ -4650,6 +4649,9 @@ int devm_of_clk_add_hw_provider(struct device *dev,
>>>         struct device_node **ptr, *np;
>>>         int ret;
>>>
>>> +       if (!dev->of_node)
>>> +               return -ENODEV;
>>> +
>>
>> Based on the other discussions, for now, just return 0. The error
>> might cause other issues in other drivers. We can clean this up later.
> 
> +1, Let's return 0 and do nothing skip the logic in the driver.
> 
> Now, from what I read in devm_of_clk_add_hw_provider(), there is a use case for
> entering with '!dev->of_node'. See get_clk_provider_node()'s usage. So I think
> we should only bail if that function fails to provide a device_node.
> 

Oh, yes, the error should have been after the get_clk_provider_node().
Any way, will send the return 0 variant too.

Cheers,
ta