linux-kernel - Re: [RFC PATCH v2 4/6] PM: opp: allow control of multiple clocks

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Date:   Tue, 12 Apr 2022 10:15:33 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Taniya Das <tdas@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: [RFC PATCH v2 4/6] PM: opp: allow control of multiple clocks

On Mon 11 Apr 08:43 PDT 2022, Krzysztof Kozlowski wrote:

> Devices might need to control several clocks when scaling the frequency
> and voltage.  Example is the Universal Flash Storage (UFS) which scales
> several independent clocks with change of performance levels.
> 
> Add parsing of multiple clocks and clock names and scale all of them,
> when needed.  If only one clock is provided, the code should behave the
> same as before.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> ---
>  drivers/opp/core.c     | 205 ++++++++++++++++++++++++++++++++---------
>  drivers/opp/of.c       |  48 ++++++++++
>  drivers/opp/opp.h      |   9 +-
>  include/linux/pm_opp.h |  23 +++++
>  4 files changed, 242 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
[..]
> @@ -1295,21 +1344,32 @@ static struct opp_table *_update_opp_table_clk(struct device *dev,
>  	 * Return early if we don't need to get clk or we have already tried it
>  	 * earlier.
>  	 */
> -	if (!getclk || IS_ERR(opp_table) || opp_table->clk)
> +	if (!getclk || IS_ERR(opp_table) || opp_table->clks)
>  		return opp_table;
>  
> +	opp_table->clks = kmalloc_array(1, sizeof(*opp_table->clks),
> +					GFP_KERNEL);

This seems to be 81 chars long, perhaps worth not line breaking?

> +	if (!opp_table->clks)
> +		return ERR_PTR(-ENOMEM);
> +
>  	/* Find clk for the device */
> -	opp_table->clk = clk_get(dev, NULL);
> +	opp_table->clks[0] = clk_get(dev, NULL);
>  
> -	ret = PTR_ERR_OR_ZERO(opp_table->clk);
> -	if (!ret)
> +	ret = PTR_ERR_OR_ZERO(opp_table->clks[0]);
> +	if (!ret) {
> +		opp_table->clk_count = 1;
>  		return opp_table;
> +	}
[..]
> +struct opp_table *dev_pm_opp_set_clknames(struct device *dev,
> +					  const char * const names[],
> +					  unsigned int count)
>  {
>  	struct opp_table *opp_table;
> -	int ret;
> +	struct clk *clk;
> +	int ret, i;
>  
>  	opp_table = _add_opp_table(dev, false);
>  	if (IS_ERR(opp_table))
> @@ -2159,70 +2259,92 @@ struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char *name)
>  	}
>  
>  	/* clk shouldn't be initialized at this point */
> -	if (WARN_ON(opp_table->clk)) {
> +	if (WARN_ON(opp_table->clks)) {
>  		ret = -EBUSY;
>  		goto err;
>  	}
>  
> -	/* Find clk for the device */
> -	opp_table->clk = clk_get(dev, name);
> -	if (IS_ERR(opp_table->clk)) {
> -		ret = dev_err_probe(dev, PTR_ERR(opp_table->clk),
> -				    "%s: Couldn't find clock\n", __func__);
> +	opp_table->clks = kmalloc_array(count, sizeof(*opp_table->clks),
> +					GFP_KERNEL);
> +	if (!opp_table->clks) {
> +		ret = -ENOMEM;
>  		goto err;
>  	}
>  
> +	for (i = 0; i < count; i++) {
> +		clk = clk_get(dev, names[i]);
> +		if (IS_ERR(clk)) {
> +			ret =  dev_err_probe(dev, PTR_ERR(clk),
> +					     "%s: Couldn't find clock %s\n",
> +					     __func__, names[i]);
> +			goto free_clks;
> +		}
> +
> +		opp_table->clks[i] = clk;
> +	}

Wouldn't it be convenient to make clks a struct clk_bulk_data array
and use clk_bulk_get()/clk_bulk_put() instead?

> +
> +	opp_table->clk_count = count;
> +
>  	return opp_table;
>  
> +free_clks:
> +	while (i != 0)
> +		clk_put(opp_table->clks[--i]);
> +
> +	kfree(opp_table->clks);
> +	opp_table->clks = NULL;
> +	opp_table->clk_count = -1;
>  err:
>  	dev_pm_opp_put_opp_table(opp_table);
>  
>  	return ERR_PTR(ret);
>  }
> -EXPORT_SYMBOL_GPL(dev_pm_opp_set_clkname);
> +EXPORT_SYMBOL_GPL(dev_pm_opp_set_clknames);
[..]
> +static int _read_clocks(struct dev_pm_opp *opp, struct opp_table *opp_table,
> +			struct device_node *np)
> +{
> +	int count, ret;
> +	u64 *freq;
> +
> +	count = of_property_count_u64_elems(np, "opp-hz");
> +	if (count < 0) {
> +		pr_err("%s: Invalid %s property (%d)\n",
> +			__func__, of_node_full_name(np), count);

Wouldn't %pOF be convenient to use here, seems like it becomes short
enough that you don't have to wrap this line then.

> +		return count;
> +	}
> +
> +	if (count != opp_table->clk_count) {
> +		pr_err("%s: number of rates %d does not match number of clocks %d in %s\n",
> +		       __func__, count, opp_table->clk_count,
> +		       of_node_full_name(np));
> +		return -EINVAL;
> +	}
> +
> +	freq = kmalloc_array(count, sizeof(*freq), GFP_KERNEL);
> +	if (!freq)
> +		return -ENOMEM;
> +
> +	ret = of_property_read_u64_array(np, "opp-hz", freq, count);
> +	if (ret) {
> +		pr_err("%s: error parsing %s: %d\n", __func__,
> +		       of_node_full_name(np), ret);
> +		ret = -EINVAL;
> +		goto free_freq;
> +	}

Regards,
Bjorn