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

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Date: Fri, 28 Jun 2024 01:17:13 +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>,
	"mturquette@...libre.com" <mturquette@...libre.com>, "sboyd@...nel.org"
	<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>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<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 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`.

Regards,
Peng.

> 
> Best regards,
> Krzysztof
>