linux-kernel - Re: [PATCH] pinctrl: renesas: rzg2l: Use BIT_ULL for PIN_CFG

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Date: Mon, 17 Jun 2024 15:36:12 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, Dan Carpenter <dan.carpenter@...aro.org>, 
	linux-renesas-soc@...r.kernel.org, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH] pinctrl: renesas: rzg2l: Use BIT_ULL for PIN_CFG_* macros

Hi Prabhakar,

On Mon, Jun 17, 2024 at 3:15 PM Prabhakar <prabhakar.csengg@...il.com> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> Commit 13a8cae6e561 ("pinctrl: renesas: rzg2l: Drop struct
> rzg2l_variable_pin_cfg") introduced a Smatch static checker warning:
>
>     drivers/pinctrl/renesas/pinctrl-rzg2l.c:374 rzg2l_pinctrl_get_variable_pin_cfg()
>     warn: was expecting a 64 bit value instead of '~((((1))) << (16))'
>
> The function `rzg2l_pinctrl_get_variable_pin_cfg` attempts to mask out
> `PIN_CFG_VARIABLE` using `BIT(16)`. However, since `pincfg` is a `u64`,
> this inadvertently masks the high 32 bits as well, which is unintended
> (on non 64-bit platforms). To correct this, `PIN_CFG_VARIABLE` should
> be defined using `BIT_ULL(16)`, ensuring proper 64-bit masking.
>
> To avoid such issues, update `PIN_CFG_*` macros to use `BIT_ULL()`.
>
> Fixes: 13a8cae6e561 ("pinctrl: renesas: rzg2l: Drop struct rzg2l_variable_pin_cfg")
> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> Closes: https://lore.kernel.org/all/5c1bf20b-7e94-4b06-95e5-da9f99750203@moroto.mountain/
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

Thanks for your patch!

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

I would like to brainstorm a bit about this, though. See below...

> --- a/drivers/pinctrl/renesas/pinctrl-rzg2l.c
> +++ b/drivers/pinctrl/renesas/pinctrl-rzg2l.c
> @@ -41,28 +41,28 @@
>  #define MUX_FUNC_MASK          GENMASK(31, 16)
>
>  /* PIN capabilities */
> -#define PIN_CFG_IOLH_A                 BIT(0)
> -#define PIN_CFG_IOLH_B                 BIT(1)
> -#define PIN_CFG_SR                     BIT(2)
> -#define PIN_CFG_IEN                    BIT(3)
> -#define PIN_CFG_PUPD                   BIT(4)
> -#define PIN_CFG_IO_VMC_SD0             BIT(5)
> -#define PIN_CFG_IO_VMC_SD1             BIT(6)
> -#define PIN_CFG_IO_VMC_QSPI            BIT(7)
> -#define PIN_CFG_IO_VMC_ETH0            BIT(8)
> -#define PIN_CFG_IO_VMC_ETH1            BIT(9)
> -#define PIN_CFG_FILONOFF               BIT(10)
> -#define PIN_CFG_FILNUM                 BIT(11)
> -#define PIN_CFG_FILCLKSEL              BIT(12)
> -#define PIN_CFG_IOLH_C                 BIT(13)
> -#define PIN_CFG_SOFT_PS                        BIT(14)
> -#define PIN_CFG_OEN                    BIT(15)
> -#define PIN_CFG_VARIABLE               BIT(16)
> -#define PIN_CFG_NOGPIO_INT             BIT(17)
> -#define PIN_CFG_NOD                    BIT(18) /* N-ch Open Drain */
> -#define PIN_CFG_SMT                    BIT(19) /* Schmitt-trigger input control */
> -#define PIN_CFG_ELC                    BIT(20)
> -#define PIN_CFG_IOLH_RZV2H             BIT(21)
> +#define PIN_CFG_IOLH_A                 BIT_ULL(0)
> +#define PIN_CFG_IOLH_B                 BIT_ULL(1)
> +#define PIN_CFG_SR                     BIT_ULL(2)
> +#define PIN_CFG_IEN                    BIT_ULL(3)
> +#define PIN_CFG_PUPD                   BIT_ULL(4)
> +#define PIN_CFG_IO_VMC_SD0             BIT_ULL(5)
> +#define PIN_CFG_IO_VMC_SD1             BIT_ULL(6)
> +#define PIN_CFG_IO_VMC_QSPI            BIT_ULL(7)
> +#define PIN_CFG_IO_VMC_ETH0            BIT_ULL(8)
> +#define PIN_CFG_IO_VMC_ETH1            BIT_ULL(9)
> +#define PIN_CFG_FILONOFF               BIT_ULL(10)
> +#define PIN_CFG_FILNUM                 BIT_ULL(11)
> +#define PIN_CFG_FILCLKSEL              BIT_ULL(12)
> +#define PIN_CFG_IOLH_C                 BIT_ULL(13)
> +#define PIN_CFG_SOFT_PS                        BIT_ULL(14)
> +#define PIN_CFG_OEN                    BIT_ULL(15)
> +#define PIN_CFG_VARIABLE               BIT_ULL(16)

PIN_CFG_VARIABLE looks a bit misplaced here, in between all the flags
indicating actual capabilities of a pin.

What about relocating it to the "high" half, and moving it next to
RZG2L_SINGLE_PIN? Perhaps even renaming it to RZG2L_CFG_VARIABLE?

> +#define PIN_CFG_NOGPIO_INT             BIT_ULL(17)
> +#define PIN_CFG_NOD                    BIT_ULL(18)     /* N-ch Open Drain */
> +#define PIN_CFG_SMT                    BIT_ULL(19)     /* Schmitt-trigger input control */
> +#define PIN_CFG_ELC                    BIT_ULL(20)
> +#define PIN_CFG_IOLH_RZV2H             BIT_ULL(21)
>
>  #define RZG2L_MPXED_COMMON_PIN_FUNCS(group) \
>                                         (PIN_CFG_IOLH_##group | \

Then the other PIN_CFG_* definitions can keep on using BIT().
To make that safer, PIN_CFG_MASK should be restricted to 32-bit:

    -#define PIN_CFG_MASK                    GENMASK_ULL(46, 0)
    +#define PIN_CFG_MASK                    GENMASK_ULL(31, 0)

and several u64 variables can be changed to u32 again.

What do you think?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds