linux-kernel - Re: [PATCH v3 3/3] ARM: da850: fix da850_set

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Date:   Tue, 6 Dec 2016 20:00:41 -0600
From:   David Lechner <david@...hnology.com>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Sekhar Nori <nsekhar@...com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Russell King <linux@...linux.org.uk>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 3/3] ARM: da850: fix da850_set_pll0rate()

On 12/05/2016 04:09 AM, Bartosz Golaszewski wrote:
> This function is confusing - its second argument is an index to the
> freq table, not the requested clock rate in Hz, but it's used as the
> set_rate callback for the pll0 clock. It leads to an oops when the
> caller doesn't know the internals and passes the rate in Hz as
> argument instead of the cpufreq index since this argument isn't bounds
> checked either.
>
> Fix it by iterating over the array of supported frequencies and
> selecting a one that matches or returning -EINVAL for unsupported
> rates.
>
> Also: update the davinci cpufreq driver. It's the only user of this
> clock and currently it passes the cpufreq table index to
> clk_set_rate(), which is confusing. Make it pass the requested clock
> rate in Hz.
>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  arch/arm/mach-davinci/da850.c     | 20 ++++++++++++++++----
>  drivers/cpufreq/davinci-cpufreq.c |  2 +-
>  2 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/mach-davinci/da850.c b/arch/arm/mach-davinci/da850.c
> index 006ec56..9837541 100644
> --- a/arch/arm/mach-davinci/da850.c
> +++ b/arch/arm/mach-davinci/da850.c
> @@ -1179,14 +1179,26 @@ static int da850_set_armrate(struct clk *clk, unsigned long index)
>  	return clk_set_rate(pllclk, index);
>  }
>
> -static int da850_set_pll0rate(struct clk *clk, unsigned long index)
> +static int da850_set_pll0rate(struct clk *clk, unsigned long rate)
>  {
> -	unsigned int prediv, mult, postdiv;
> -	struct da850_opp *opp;
>  	struct pll_data *pll = clk->pll_data;
> +	struct cpufreq_frequency_table *freq;
> +	unsigned int prediv, mult, postdiv;
> +	struct da850_opp *opp = NULL;
>  	int ret;
>
> -	opp = (struct da850_opp *) cpufreq_info.freq_table[index].driver_data;
> +	for (freq = da850_freq_table;
> +	     freq->frequency != CPUFREQ_TABLE_END; freq++) {
> +		/* rate is in Hz, freq->frequency is in KHz */
> +		if (freq->frequency == rate / 1000) {
> +			opp = (struct da850_opp *)freq->driver_data;
> +			break;
> +		}
> +	}
> +
> +	if (opp == NULL)

Would be simpler to write:

	if (!opp)

> +		return -EINVAL;
> +
>  	prediv = opp->prediv;
>  	mult = opp->mult;
>  	postdiv = opp->postdiv;
> diff --git a/drivers/cpufreq/davinci-cpufreq.c b/drivers/cpufreq/davinci-cpufreq.c
> index b95a872..d54a27c 100644
> --- a/drivers/cpufreq/davinci-cpufreq.c
> +++ b/drivers/cpufreq/davinci-cpufreq.c
> @@ -55,7 +55,7 @@ static int davinci_target(struct cpufreq_policy *policy, unsigned int idx)
>  			return ret;
>  	}
>
> -	ret = clk_set_rate(armclk, idx);
> +	ret = clk_set_rate(armclk, new_freq * 1000);
>  	if (ret)
>  		return ret;
>
>