linux-kernel - [PATCH] drm/panfrost: Enable devfreq to work without regulator

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Message-Id: <20190816093107.30518-1-steven.price@arm.com>
Date:   Fri, 16 Aug 2019 10:31:05 +0100
From:   Steven Price <steven.price@....com>
To:     Rob Herring <robh@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Steven Price <steven.price@....com>
Subject: [PATCH] drm/panfrost: Enable devfreq to work without regulator

If there is no regulator defined for the GPU then still control the
frequency using the supplied clock.

Some boards have clock control but no (direct) control of the regulator.
For example the HiKey960 uses a mailbox protocol to a MCU to control
frequencies and doesn't directly control the voltage. This patch allows
frequency control of the GPU on this system.

Signed-off-by: Steven Price <steven.price@....com>
---
 drivers/gpu/drm/panfrost/panfrost_devfreq.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
index a7c18bceb7fd..77e1ad24de53 100644
--- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
+++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
@@ -39,7 +39,7 @@ static int panfrost_devfreq_target(struct device *dev, unsigned long *freq,
 	 * If frequency scaling from low to high, adjust voltage first.
 	 * If frequency scaling from high to low, adjust frequency first.
 	 */
-	if (old_clk_rate < target_rate) {
+	if (old_clk_rate < target_rate && pfdev->regulator) {
 		err = regulator_set_voltage(pfdev->regulator, target_volt,
 					    target_volt);
 		if (err) {
@@ -58,7 +58,7 @@ static int panfrost_devfreq_target(struct device *dev, unsigned long *freq,
 		return err;
 	}
 
-	if (old_clk_rate > target_rate) {
+	if (old_clk_rate > target_rate && pfdev->regulator) {
 		err = regulator_set_voltage(pfdev->regulator, target_volt,
 					    target_volt);
 		if (err)
@@ -136,9 +136,6 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
 	int ret;
 	struct dev_pm_opp *opp;
 
-	if (!pfdev->regulator)
-		return 0;
-
 	ret = dev_pm_opp_of_add_table(&pfdev->pdev->dev);
 	if (ret == -ENODEV) /* Optional, continue without devfreq */
 		return 0;
-- 
2.20.1