Currently it's not possible to set just the bandwidth if the OPP
describes other properties (required-opps, opp-hz etc.).

Introduce dev_pm_opp_set_bw() to solve this problem.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
---
 drivers/opp/core.c     | 28 ++++++++++++++++++++++++++++
 include/linux/pm_opp.h |  6 ++++++
 2 files changed, 34 insertions(+)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 85cbc8de407c..00d7f7c20189 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1278,6 +1278,34 @@ int dev_pm_opp_set_opp(struct device *dev, struct dev_pm_opp *opp)
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_set_opp);
 
+/**
+ * dev_pm_opp_set_bw() - Configure device's interconnect bandwidth from OPP
+ * @dev: device for which we do this operation
+ * @opp: OPP to get the bandwidth data from
+ *
+ * This configures the interconnect bandwidth based on the properties of the
+ * OPP passed to this routine.
+ *
+ * Return: 0 on success, a negative error number otherwise.
+ */
+int dev_pm_opp_set_bw(struct device *dev, struct dev_pm_opp *opp)
+{
+	struct opp_table *opp_table;
+	int ret;
+
+	opp_table = _find_opp_table(dev);
+	if (IS_ERR(opp_table)) {
+		dev_err(dev, "%s: device opp doesn't exist\n", __func__);
+		return PTR_ERR(opp_table);
+	}
+
+	ret = _set_opp_bw(opp_table, opp, dev);
+	dev_pm_opp_put_opp_table(opp_table);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_set_bw);
+
 /* OPP-dev Helpers */
 static void _remove_opp_dev(struct opp_device *opp_dev,
 			    struct opp_table *opp_table)
diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index dc1fb5890792..5e074ac7a68e 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -167,6 +167,7 @@ struct dev_pm_opp *dev_pm_opp_xlate_required_opp(struct opp_table *src_table, st
 int dev_pm_opp_xlate_performance_state(struct opp_table *src_table, struct opp_table *dst_table, unsigned int pstate);
 int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq);
 int dev_pm_opp_set_opp(struct device *dev, struct dev_pm_opp *opp);
+int dev_pm_opp_set_bw(struct device *dev, struct dev_pm_opp *opp);
 int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, const struct cpumask *cpumask);
 int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask);
 void dev_pm_opp_remove_table(struct device *dev);
@@ -373,6 +374,11 @@ static inline int dev_pm_opp_set_opp(struct device *dev, struct dev_pm_opp *opp)
 	return -EOPNOTSUPP;
 }
 
+static inline int dev_pm_opp_set_bw(struct device *dev, struct dev_pm_opp *opp)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, const struct cpumask *cpumask)
 {
 	return -EOPNOTSUPP;

---
base-commit: 6a3d37b4d885129561e1cef361216f00472f7d2e
change-id: 20230526-topic-opp_bw-8d04a85a93a8

Best regards,
-- 
Konrad Dybcio <konrad.dybcio@linaro.org>

On 26-05-23, 11:17, Konrad Dybcio wrote:
> Currently it's not possible to set just the bandwidth if the OPP
> describes other properties (required-opps, opp-hz etc.).
> 
> Introduce dev_pm_opp_set_bw() to solve this problem.

The OPP core (intentionally) doesn't provide any such interface for
freq, volt, bw, level, etc.

Setting just one of the properties for a device is potentially harmful and the
OPP must be set as a whole and so this isn't allowed. There is
dev_pm_opp_set_freq(), but it uses freq to just find the OPP and sets entire OPP
only.

Why should be break this for bw ?

-- 
viresh

On 26.05.2023 12:53, Viresh Kumar wrote:
> On 26-05-23, 11:17, Konrad Dybcio wrote:
>> Currently it's not possible to set just the bandwidth if the OPP
>> describes other properties (required-opps, opp-hz etc.).
>>
>> Introduce dev_pm_opp_set_bw() to solve this problem.
> 
> The OPP core (intentionally) doesn't provide any such interface for
> freq, volt, bw, level, etc.
> 
> Setting just one of the properties for a device is potentially harmful and the
> OPP must be set as a whole and so this isn't allowed. There is
> dev_pm_opp_set_freq(), but it uses freq to just find the OPP and sets entire OPP
> only.
> 
> Why should be break this for bw ?
> 
There are some users which have tight power sequencing requirements,
like the Qualcomm Adreno GPU.

Dropping the entire OPP kills clocks, bw and required-opps at once,
but on certain Adrenos we need something like:


disable memory clock (clk)
disable all other clocks, including the opp-managed core clock (clk_bulk)
kill one, fully manually controlled genpd (manual runtime pm)
remove bus vote (func proposed in this patch)
kill another genpd (manual runtime pm)
kill the opp-managed genpd (automatic pm calls)

Changing the order kills the chip until you reboot the whole board and
setting freq=0 using dev_pm_opp_set_rate doesn't drop the bw vote.

Konrad