linux-kernel - [PATCH] opp: Update bandwidth requirements based on scaling up/down

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Date:   Thu, 28 Jan 2021 15:36:39 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Dmitry Osipenko <digetx@...il.com>,
        Akhil P Oommen <akhilpo@...eaurora.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] opp: Update bandwidth requirements based on scaling up/down

The bandwidth must be scaled at a different point in the code flow based
on if we are scaling up or down the frequency, otherwise this may cause
undesired effects as the device will try to use more of the memory
bandwidth which may be shared across several devices. Much like how
regulators and required-opps are programmed.

Reported-by: Dmitry Osipenko <digetx@...il.com>
Reported-by: Akhil P Oommen <akhilpo@...eaurora.org>
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/opp/core.c | 40 +++++++++++++++++++++++++++-------------
 1 file changed, 27 insertions(+), 13 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index e03600547b98..a518173fd64a 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1015,8 +1015,16 @@ static int _set_opp(struct device *dev, struct opp_table *opp_table,
 	/* Scaling up? Configure required OPPs before frequency */
 	if (!scaling_down) {
 		ret = _set_required_opps(dev, opp_table, opp, true);
-		if (ret)
+		if (ret) {
+			dev_err(dev, "Failed to set required opps: %d\n", ret);
+			return ret;
+		}
+
+		ret = _set_opp_bw(opp_table, opp, dev);
+		if (ret) {
+			dev_err(dev, "Failed to set bw: %d\n", ret);
 			return ret;
+		}
 	}
 
 	if (opp_table->set_opp) {
@@ -1029,24 +1037,30 @@ static int _set_opp(struct device *dev, struct opp_table *opp_table,
 		ret = _generic_set_opp_clk_only(dev, opp_table->clk, freq);
 	}
 
+	if (ret)
+		return ret;
+
 	/* Scaling down? Configure required OPPs after frequency */
-	if (!ret && scaling_down) {
+	if (scaling_down) {
+		ret = _set_opp_bw(opp_table, opp, dev);
+		if (ret) {
+			dev_err(dev, "Failed to set bw: %d\n", ret);
+			return ret;
+		}
+
 		ret = _set_required_opps(dev, opp_table, opp, false);
-		if (ret)
+		if (ret) {
 			dev_err(dev, "Failed to set required opps: %d\n", ret);
+			return ret;
+		}
 	}
 
-	if (!ret) {
-		ret = _set_opp_bw(opp_table, opp, dev);
-		if (!ret) {
-			opp_table->enabled = true;
-			dev_pm_opp_put(old_opp);
+	opp_table->enabled = true;
+	dev_pm_opp_put(old_opp);
 
-			/* Make sure current_opp doesn't get freed */
-			dev_pm_opp_get(opp);
-			opp_table->current_opp = opp;
-		}
-	}
+	/* Make sure current_opp doesn't get freed */
+	dev_pm_opp_get(opp);
+	opp_table->current_opp = opp;
 
 	return ret;
 }
-- 
2.25.0.rc1.19.g042ed3e048af