Re: [PATCH v2 2/4] devfreq: exynos-bus: convert to use dev_pm_opp_set_rate()

Chanwoo Choi
2019-07-16T03:53:24Z

Hi Kamil,

Looks good to me. But, this patch has some issue.
I added the detailed reviews.

I recommend that you make the separate patches as following
in order to clarify the role of which apply the dev_pm_opp_* function.

First patch,
Need to consolidate the following two function into one function.
because the original exynos-bus.c has the problem that the regulator
of parent devfreq device have to be enabled before enabling the clock.
This issue did not happen because bootloader enables the bus-related
regulators before kernel booting.
- exynos_bus_parse_of()
- exynos_bus_parent_parse_of()

Second patch,
Apply dev_pm_opp_set_regulators() and dev_pm_opp_set_rate()

On 19. 7. 15. 오후 9:04, Kamil Konieczny wrote:
> Reuse opp core code for setting bus clock and voltage. As a side
> effect this allow useage of coupled regulators feature (required
> for boards using Exynos5422/5800 SoCs) because dev_pm_opp_set_rate()
> uses regulator_set_voltage_triplet() for setting regulator voltage
> while the old code used regulator_set_voltage_tol() with fixed
> tolerance. This patch also removes no longer needed parsing of DT
> property "exynos,voltage-tolerance" (no Exynos devfreq DT node uses
> it).
>
> Signed-off-by: Kamil Konieczny <k.konieczny@partner.samsung.com>
> ---
> drivers/devfreq/exynos-bus.c | 172 ++++++++++++++---------------------
> 1 file changed, 66 insertions(+), 106 deletions(-)
>
> diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
> index 486cc5b422f1..7fc4f76bd848 100644
> --- a/drivers/devfreq/exynos-bus.c
> +++ b/drivers/devfreq/exynos-bus.c
> @@ -25,7 +25,6 @@
> #include <linux/slab.h>
>
> #define DEFAULT_SATURATION_RATIO 40
> -#define DEFAULT_VOLTAGE_TOLERANCE 2
>
> struct exynos_bus {
> struct device *dev;
> @@ -37,9 +36,9 @@ struct exynos_bus {
>
> unsigned long curr_freq;
>
> - struct regulator *regulator;
> + struct opp_table *opp_table;
> +
> struct clk *clk;
> - unsigned int voltage_tolerance;
> unsigned int ratio;
> };
>
> @@ -99,56 +98,25 @@ static int exynos_bus_target(struct device *dev, unsigned long *freq, u32 flags)
> {
> struct exynos_bus *bus = dev_get_drvdata(dev);
> struct dev_pm_opp *new_opp;
> - unsigned long old_freq, new_freq, new_volt, tol;
> int ret = 0;
> -
> - /* Get new opp-bus instance according to new bus clock */
> + /*
> + * New frequency for bus may not be exactly matched to opp, adjust
> + * *freq to correct value.
> + */

You better to change this comment with following styles
to keep the consistency:

/* Get correct frequency for bus ... */

> new_opp = devfreq_recommended_opp(dev, freq, flags);
> if (IS_ERR(new_opp)) {
> dev_err(dev, "failed to get recommended opp instance\n");
> return PTR_ERR(new_opp);
> }
>
> - new_freq = dev_pm_opp_get_freq(new_opp);
> - new_volt = dev_pm_opp_get_voltage(new_opp);
> dev_pm_opp_put(new_opp);
>
> - old_freq = bus->curr_freq;
> -
> - if (old_freq == new_freq)
> - return 0;
> - tol = new_volt * bus->voltage_tolerance / 100;
> -
> /* Change voltage and frequency according to new OPP level */
> mutex_lock(&bus->lock);
> + ret = dev_pm_opp_set_rate(dev, *freq);
> + if (!ret)
> + bus->curr_freq = *freq;

Have to print the error log if ret has minus error value.
Modify it as following:

if (ret < 0) {
dev_err(dev, "failed to set bus rate\n");
goto err:
}
bus->curr_freq = *freq;

err:
mutex_unlock(&bus->lock);

return ret;

>
> - if (old_freq < new_freq) {
> - ret = regulator_set_voltage_tol(bus->regulator, new_volt, tol);
> - if (ret < 0) {
> - dev_err(bus->dev, "failed to set voltage\n");
> - goto out;
> - }
> - }
> -
> - ret = clk_set_rate(bus->clk, new_freq);
> - if (ret < 0) {
> - dev_err(dev, "failed to change clock of bus\n");
> - clk_set_rate(bus->clk, old_freq);
> - goto out;
> - }
> -
> - if (old_freq > new_freq) {
> - ret = regulator_set_voltage_tol(bus->regulator, new_volt, tol);
> - if (ret < 0) {
> - dev_err(bus->dev, "failed to set voltage\n");
> - goto out;
> - }
> - }
> - bus->curr_freq = new_freq;
> -
> - dev_dbg(dev, "Set the frequency of bus (%luHz -> %luHz, %luHz)\n",
> - old_freq, new_freq, clk_get_rate(bus->clk));
> -out:
> mutex_unlock(&bus->lock);
>
> return ret;
> @@ -194,10 +162,11 @@ static void exynos_bus_exit(struct device *dev)
> if (ret < 0)
> dev_warn(dev, "failed to disable the devfreq-event devices\n");
>
> - if (bus->regulator)
> - regulator_disable(bus->regulator);
> + if (bus->opp_table)
> + dev_pm_opp_put_regulators(bus->opp_table);

Have to disable regulator after disabling the clock
to prevent the h/w fault.

I think that you should call them with following sequence:

clk_disable_unprepare(bus->clk);
if (bus->opp_table)
dev_pm_opp_put_regulators(bus->opp_table);
dev_pm_opp_of_remove_table(dev);

>
> dev_pm_opp_of_remove_table(dev);
> +
> clk_disable_unprepare(bus->clk);
> }
>
> @@ -209,39 +178,26 @@ static int exynos_bus_passive_target(struct device *dev, unsigned long *freq,
> {
> struct exynos_bus *bus = dev_get_drvdata(dev);
> struct dev_pm_opp *new_opp;
> - unsigned long old_freq, new_freq;
> - int ret = 0;
> + int ret;
>
> - /* Get new opp-bus instance according to new bus clock */
> + /*
> + * New frequency for bus may not be exactly matched to opp, adjust
> + * *freq to correct value.
> + */

You better to change this comment with following styles
to keep the consistency:

/* Get correct frequency for bus ... */

> new_opp = devfreq_recommended_opp(dev, freq, flags);
> if (IS_ERR(new_opp)) {
> dev_err(dev, "failed to get recommended opp instance\n");
> return PTR_ERR(new_opp);
> }
>
> - new_freq = dev_pm_opp_get_freq(new_opp);
> dev_pm_opp_put(new_opp);
>
> - old_freq = bus->curr_freq;
> -
> - if (old_freq == new_freq)
> - return 0;
> -
> /* Change the frequency according to new OPP level */
> mutex_lock(&bus->lock);
> + ret = dev_pm_opp_set_rate(dev, *freq);
> + if (!ret)
> + bus->curr_freq = *freq;

ditto. Have to print the error log, check above comment.

>
> - ret = clk_set_rate(bus->clk, new_freq);
> - if (ret < 0) {
> - dev_err(dev, "failed to set the clock of bus\n");
> - goto out;
> - }
> -
> - *freq = new_freq;
> - bus->curr_freq = new_freq;
> -
> - dev_dbg(dev, "Set the frequency of bus (%luHz -> %luHz, %luHz)\n",
> - old_freq, new_freq, clk_get_rate(bus->clk));
> -out:
> mutex_unlock(&bus->lock);
>
> return ret;
> @@ -259,20 +215,7 @@ static int exynos_bus_parent_parse_of(struct device_node *np,
> struct exynos_bus *bus)
> {
> struct device *dev = bus->dev;
> - int i, ret, count, size;
> -
> - /* Get the regulator to provide each bus with the power */
> - bus->regulator = devm_regulator_get(dev, "vdd");
> - if (IS_ERR(bus->regulator)) {
> - dev_err(dev, "failed to get VDD regulator\n");
> - return PTR_ERR(bus->regulator);
> - }
> -
> - ret = regulator_enable(bus->regulator);
> - if (ret < 0) {
> - dev_err(dev, "failed to enable VDD regulator\n");
> - return ret;
> - }
> + int i, count, size;
>
> /*
> * Get the devfreq-event devices to get the current utilization of
> @@ -281,24 +224,20 @@ static int exynos_bus_parent_parse_of(struct device_node *np,
> count = devfreq_event_get_edev_count(dev);
> if (count < 0) {
> dev_err(dev, "failed to get the count of devfreq-event dev\n");
> - ret = count;
> - goto err_regulator;
> + return count;
> }
> +
> bus->edev_count = count;
>
> size = sizeof(*bus->edev) * count;
> bus->edev = devm_kzalloc(dev, size, GFP_KERNEL);
> - if (!bus->edev) {
> - ret = -ENOMEM;
> - goto err_regulator;
> - }
> + if (!bus->edev)
> + return -ENOMEM;
>
> for (i = 0; i < count; i++) {
> bus->edev[i] = devfreq_event_get_edev_by_phandle(dev, i);
> - if (IS_ERR(bus->edev[i])) {
> - ret = -EPROBE_DEFER;
> - goto err_regulator;
> - }
> + if (IS_ERR(bus->edev[i]))
> + return -EPROBE_DEFER;
> }
>
> /*
> @@ -314,22 +253,15 @@ static int exynos_bus_parent_parse_of(struct device_node *np,
> if (of_property_read_u32(np, "exynos,saturation-ratio", &bus->ratio))
> bus->ratio = DEFAULT_SATURATION_RATIO;
>
> - if (of_property_read_u32(np, "exynos,voltage-tolerance",
> - &bus->voltage_tolerance))
> - bus->voltage_tolerance = DEFAULT_VOLTAGE_TOLERANCE;
> -
> return 0;
> -
> -err_regulator:
> - regulator_disable(bus->regulator);
> -
> - return ret;
> }
>
> static int exynos_bus_parse_of(struct device_node *np,
> - struct exynos_bus *bus)
> + struct exynos_bus *bus, bool passive)
> {
> struct device *dev = bus->dev;
> + struct opp_table *opp_table;
> + const char *vdd = "vdd";
> struct dev_pm_opp *opp;
> unsigned long rate;
> int ret;
> @@ -347,11 +279,22 @@ static int exynos_bus_parse_of(struct device_node *np,
> return ret;
> }
>
> + if (!passive) {
> + opp_table = dev_pm_opp_set_regulators(dev, &vdd, 1);
> + if (IS_ERR(opp_table)) {
> + ret = PTR_ERR(opp_table);
> + dev_err(dev, "failed to set regulators %d\n", ret);
> + goto err_clk;/
> + }
> +
> + bus->opp_table = opp_table;
> + }

This driver has exynos_bus_parent_parse_of() function for parent devfreq device.
dev_pm_opp_set_regulators() have to be called in exynos_bus_parent_parse_of()
because the regulator is only used by parent devfreq device.

> +
> /* Get the freq and voltage from OPP table to scale the bus freq */
> ret = dev_pm_opp_of_add_table(dev);
> if (ret < 0) {
> dev_err(dev, "failed to get OPP table\n");
> - goto err_clk;
> + goto err_regulator;
> }
>
> rate = clk_get_rate(bus->clk);
> @@ -362,6 +305,7 @@ static int exynos_bus_parse_of(struct device_node *np,
> ret = PTR_ERR(opp);
> goto err_opp;
> }
> +
> bus->curr_freq = dev_pm_opp_get_freq(opp);
> dev_pm_opp_put(opp);
>
> @@ -369,6 +313,13 @@ static int exynos_bus_parse_of(struct device_node *np,
>
> err_opp:
> dev_pm_opp_of_remove_table(dev);
> +
> +err_regulator:
> + if (bus->opp_table) {
> + dev_pm_opp_put_regulators(bus->opp_table);
> + bus->opp_table = NULL;
> + }

As I mentioned above, it it wrong to call dev_pm_opp_put_regulators()
after removing the opp_table by dev_pm_opp_of_remove_table().

> +
> err_clk:
> clk_disable_unprepare(bus->clk);
>
> @@ -386,6 +337,7 @@ static int exynos_bus_probe(struct platform_device *pdev)
> struct exynos_bus *bus;
> int ret, max_state;
> unsigned long min_freq, max_freq;
> + bool passive = false;
>
> if (!np) {
> dev_err(dev, "failed to find devicetree node\n");
> @@ -395,12 +347,18 @@ static int exynos_bus_probe(struct platform_device *pdev)
> bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
> if (!bus)
> return -ENOMEM;
> +
> mutex_init(&bus->lock);
> bus->dev = &pdev->dev;
> platform_set_drvdata(pdev, bus);
> + node = of_parse_phandle(dev->of_node, "devfreq", 0);
> + if (node) {
> + of_node_put(node);
> + passive = true;
> + }
>
> /* Parse the device-tree to get the resource information */
> - ret = exynos_bus_parse_of(np, bus);
> + ret = exynos_bus_parse_of(np, bus, passive);
> if (ret < 0)
> return ret;
>
> @@ -410,13 +368,10 @@ static int exynos_bus_probe(struct platform_device *pdev)
> goto err;
> }
>
> - node = of_parse_phandle(dev->of_node, "devfreq", 0);
> - if (node) {
> - of_node_put(node);
> + if (passive)
> goto passive;
> - } else {
> - ret = exynos_bus_parent_parse_of(np, bus);
> - }
> +
> + ret = exynos_bus_parent_parse_of(np, bus);
>

Remove unneeded blank line.

> if (ret < 0)
> goto err;
> @@ -509,6 +464,11 @@ static int exynos_bus_probe(struct platform_device *pdev)
>
> err:
> dev_pm_opp_of_remove_table(dev);
> + if (bus->opp_table) {
> + dev_pm_opp_put_regulators(bus->opp_table);
> + bus->opp_table = NULL;
> + }
> +

ditto.
Have to disable regulator after disabling the clock
to prevent the h/w fault.

I think that you should call them with following sequence:

clk_disable_unprepare(bus->clk);
if (bus->opp_table)
dev_pm_opp_put_regulators(bus->opp_table);
dev_pm_opp_of_remove_table(dev);

> clk_disable_unprepare(bus->clk);
>
> return ret;
>

--
Best Regards,
Chanwoo Choi