linux-kernel - RE: [PATCH 1/2] clk: imx93: Drop macro IMX93_CLK

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Message-ID:
 <AM6PR04MB5941D63D1AD2CE63E8D0388F88D02@AM6PR04MB5941.eurprd04.prod.outlook.com>
Date: Fri, 28 Jun 2024 06:28:38 +0000
From: Peng Fan <peng.fan@....com>
To: Krzysztof Kozlowski <krzk@...nel.org>, Pengfei Li <pengfei.li_1@....com>
CC: "krzk+dt@...nel.org" <krzk+dt@...nel.org>, "robh@...nel.org"
	<robh@...nel.org>, "abelvesa@...nel.org" <abelvesa@...nel.org>,
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	<sboyd@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
	"shawnguo@...nel.org" <shawnguo@...nel.org>, "s.hauer@...gutronix.de"
	<s.hauer@...gutronix.de>, Jacky Bai <ping.bai@....com>, Ye Li
	<ye.li@....com>, Aisheng Dong <aisheng.dong@....com>, Frank Li
	<frank.li@....com>, "kernel@...gutronix.de" <kernel@...gutronix.de>,
	"festevam@...il.com" <festevam@...il.com>, "linux-clk@...r.kernel.org"
	<linux-clk@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
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	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] clk: imx93: Drop macro IMX93_CLK_END

> Subject: Re: [PATCH 1/2] clk: imx93: Drop macro IMX93_CLK_END
> 
> On 28/06/2024 03:17, Peng Fan wrote:
> >> Subject: Re: [PATCH 1/2] clk: imx93: Drop macro IMX93_CLK_END
> >>
> >> 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@....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.
> >
> > But there is issue that binding update and clock driver are normally
> > in two patches.  So if just use the IMX93_CLK_END in this file, it
> > will be easy to break `git bisect`.
> 
> There is no issue. Srsly, this would be the only, only one driver having
> that issue.
> 
> How is this even possible? How adding one new define for pre-
> processor would cause driver issues or some sort of bisectability
> problems?

Ah, I was wrong, I just thought driver update is applied first.

With binding update applied first, then driver update applied,
there is no issue.

Regards,
Peng.

> 
> These are basics of C we talk about now...
> 
> Best regards,
> Krzysztof
>