Re: [PATCH 1/2] clk: imx93: Drop macro IMX93_CLK_END

[Krzysztof Kozlowski <krzk@kernel.org>]

On 25/06/2024 12:43, Pengfei Li wrote:
> On Tue, Jun 25, 2024 at 09:44:42AM +0200, Krzysztof Kozlowski wrote:
>> On 25/06/2024 19:51, Pengfei Li wrote:
>>> IMX93_CLK_END was previously defined in imx93-clock.h to
>>> indicate the number of clocks, but it is not part of the
>>> ABI, so it should be dropped.
>>>
>>> Now, the driver gets the number of clks by querying the
>>> maximum index in the clk array. Due to the discontinuity
>>> in the definition of clk index, with some gaps present,
>>> the total count cannot be obtained by summing the array
>>> size.
>>>
>>> Signed-off-by: Pengfei Li <pengfei.li_1@nxp.com>
>>> ---
>>>  drivers/clk/imx/clk-imx93.c | 25 +++++++++++++++++++++----
>>>  1 file changed, 21 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/clk/imx/clk-imx93.c b/drivers/clk/imx/clk-imx93.c
>>> index c6a9bc8ecc1f..68c929512e16 100644
>>> --- a/drivers/clk/imx/clk-imx93.c
>>> +++ b/drivers/clk/imx/clk-imx93.c
>>> @@ -257,6 +257,20 @@ static const struct imx93_clk_ccgr {
>>>  static struct clk_hw_onecell_data *clk_hw_data;
>>>  static struct clk_hw **clks;
>>>  
>>> +static int imx_clks_get_num(void)
>>> +{
>>> +	u32 val = 0;
>>> +	int i;
>>> +
>>> +	for (i = 0; i < ARRAY_SIZE(root_array); i++)
>>> +		val = max_t(u32, val, root_array[i].clk);
>>> +
>>> +	for (i = 0; i < ARRAY_SIZE(ccgr_array); i++)
>>> +		val = max_t(u32, val, ccgr_array[i].clk);
>>> +
>>> +	return val + 1;
>>> +}
>>> +
>>>  static int imx93_clocks_probe(struct platform_device *pdev)
>>>  {
>>>  	struct device *dev = &pdev->dev;
>>> @@ -264,14 +278,17 @@ static int imx93_clocks_probe(struct platform_device *pdev)
>>>  	const struct imx93_clk_root *root;
>>>  	const struct imx93_clk_ccgr *ccgr;
>>>  	void __iomem *base, *anatop_base;
>>> +	int clks_num;
>>>  	int i, ret;
>>>  
>>> +	clks_num = imx_clks_get_num();
>>> +
>>>  	clk_hw_data = devm_kzalloc(dev, struct_size(clk_hw_data, hws,
>>> -					  IMX93_CLK_END), GFP_KERNEL);
>>> +					  clks_num), GFP_KERNEL);
>>>  	if (!clk_hw_data)
>>>  		return -ENOMEM;
>>>  
>>> -	clk_hw_data->num = IMX93_CLK_END;
>>> +	clk_hw_data->num = clks_num;
>>
>> Why so complicated code instead of pre-processor define or array size?
>>
>> Best regards,
>> Krzysztof
>>
>>
> 
> Hi Krzysztof,
> 
> Thanks for the comment, here are some of our thoughts.
> 
> Regarding the predefined method, it's easy to forget to update the macro definition when adding some new clocks to
> imx93-clock.h in the future.

Somehow most developers in most platforms can do it... Anyway, that
would be build time detectable so no problem at all.

> 
> Also, we cannot use the array size method in this scenario, as some unnecessary clocks have been removed in the past,
> resulting in discontinuous definitions of clock indexes. This means that the maximum clock index can be larger than
> the allocated clk_hw array size. At this point, using the maximum index to access the clk_hw array will result in an
> out of bounds error.

You mix bindings with array entries. That's independent or just clock
drivers are broken.

Best regards,
Krzysztof