linux-kernel - Re: [PATCH 2/2] drivers: clk: st: address sparse warnings

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Date:   Wed, 25 Jul 2018 13:40:53 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Michael Turquette <mturquette@...libre.com>,
        Nicholas Mc Guire <hofrat@...dl.org>
Cc:     Kees Cook <keescook@...omium.org>, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, Nicholas Mc Guire <hofrat@...dl.org>
Subject: Re: [PATCH 2/2] drivers: clk: st: address sparse warnings

Quoting Nicholas Mc Guire (2018-07-15 03:18:24)
>  Refactoring of code to make it more readable and at the same time make
> sparse happy again.
> 
> Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> ---
> 
> sparse complained about:
> drivers/clk/st/clkgen-pll.c:225:12: warning: context imbalance in 'clkgen_pll_enable' - different lock contexts for basic block
> drivers/clk/st/clkgen-pll.c:267:9: warning: context imbalance in 'clkgen_pll_disable' - different lock contexts for basic block
> drivers/clk/st/clkgen-pll.c:413:9: warning: context imbalance in 'set_rate_stm_pll3200c32' - different lock contexts for basic block
> drivers/clk/st/clkgen-pll.c:570:9: warning: context imbalance in 'set_rate_stm_pll4600c28' - different lock contexts for basic block
> 
> Which are technically false positives as the pll->lock which is being
> checked is determined at configuration time, thus the locks are balanced.
> Never the less the refactored code seems more readable and was 
> commented to make it clear.

This stuff above should go into the commit text.

> 
> Patch was compile tested with: multi_v7_defconfig (implies
> CONFIG_ARCH_STI=y)
> 
> Patch is against 4.18-rc4 (localversion-next is next-20180713)
> 
>  drivers/clk/st/clkgen-pll.c | 51 +++++++++++++++++++++++++--------------------
>  1 file changed, 28 insertions(+), 23 deletions(-)

I believe this driver is in stasis mode. Not sure anyone is testing this
right now. Please Cc people who have worked on this driver, like Gabriel
Fernandez.
 
> 
> diff --git a/drivers/clk/st/clkgen-pll.c b/drivers/clk/st/clkgen-pll.c
> index 7a7106dc..cbb5184 100644
> --- a/drivers/clk/st/clkgen-pll.c
> +++ b/drivers/clk/st/clkgen-pll.c
> @@ -228,13 +228,13 @@ static int clkgen_pll_enable(struct clk_hw *hw)
>         unsigned long flags = 0;
>         int ret = 0;
>  
> -       if (pll->lock)
> +       if (pll->lock) {
> +               /* stih418 and stih407 */
>                 spin_lock_irqsave(pll->lock, flags);
> -
> -       ret = __clkgen_pll_enable(hw);
> -
> -       if (pll->lock)
> +               ret = __clkgen_pll_enable(hw);
>                 spin_unlock_irqrestore(pll->lock, flags);
> +       } else
> +               ret = __clkgen_pll_enable(hw);
>  
>         return ret;
>  }
> @@ -259,13 +259,13 @@ static void clkgen_pll_disable(struct clk_hw *hw)
>         struct clkgen_pll *pll = to_clkgen_pll(hw);
>         unsigned long flags = 0;
>  
> -       if (pll->lock)
> +       if (pll->lock) {
> +               /* stih418 and stih407 */
>                 spin_lock_irqsave(pll->lock, flags);
> -
> -       __clkgen_pll_disable(hw);
> -
> -       if (pll->lock)
> +               __clkgen_pll_disable(hw);
>                 spin_unlock_irqrestore(pll->lock, flags);
> +       } else
> +               __clkgen_pll_disable(hw);
>  }
>  
>  static int clk_pll3200c32_get_params(unsigned long input, unsigned long output,
> @@ -400,15 +400,18 @@ static int set_rate_stm_pll3200c32(struct clk_hw *hw, unsigned long rate,
>  
>         __clkgen_pll_disable(hw);
>  
> -       if (pll->lock)
> +       if (pll->lock) {
> +               /* stih407 and stih418 */
>                 spin_lock_irqsave(pll->lock, flags);
> -
> -       CLKGEN_WRITE(pll, ndiv, pll->ndiv);
> -       CLKGEN_WRITE(pll, idf, pll->idf);
> -       CLKGEN_WRITE(pll, cp, pll->cp);
> -
> -       if (pll->lock)
> +               CLKGEN_WRITE(pll, ndiv, pll->ndiv);
> +               CLKGEN_WRITE(pll, idf, pll->idf);
> +               CLKGEN_WRITE(pll, cp, pll->cp);
>                 spin_unlock_irqrestore(pll->lock, flags);
> +       } else {
> +               CLKGEN_WRITE(pll, ndiv, pll->ndiv);
> +               CLKGEN_WRITE(pll, idf, pll->idf);
> +               CLKGEN_WRITE(pll, cp, pll->cp);
> +       }

Please don't duplicate this code. The sparse warnings can be fixed by
adding a fake lock acquire to the else of the if condition. We do this
in drivers/clk/clk.c so you should be able to copy it from there.

>