linux-kernel - [RFC PATCH 2/3] drm/imagination: fix clock control on the J722S

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Message-Id: <20250716134717.4085567-3-mwalle@kernel.org>
Date: Wed, 16 Jul 2025 15:47:16 +0200
From: Michael Walle <mwalle@...nel.org>
To: Frank Binns <frank.binns@...tec.com>,
	Matt Coster <matt.coster@...tec.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Nishanth Menon <nm@...com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Tero Kristo <kristo@...nel.org>
Cc: dri-devel@...ts.freedesktop.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Michael Walle <mwalle@...nel.org>
Subject: [RFC PATCH 2/3] drm/imagination: fix clock control on the J722S

The J722S won't let you set the clock frequency if there is no device
using it. Thus, the assigned-clocks property won't work per se.

As a workaround, set the clock again during the probing of the driver.

Signed-off-by: Michael Walle <mwalle@...nel.org>
---
 drivers/gpu/drm/imagination/pvr_device.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/imagination/pvr_device.c b/drivers/gpu/drm/imagination/pvr_device.c
index 8b9ba4983c4c..e7a7cc1bdf93 100644
--- a/drivers/gpu/drm/imagination/pvr_device.c
+++ b/drivers/gpu/drm/imagination/pvr_device.c
@@ -16,6 +16,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/clk.h>
+#include <linux/clk/clk-conf.h>
 #include <linux/compiler_attributes.h>
 #include <linux/compiler_types.h>
 #include <linux/dma-mapping.h>
@@ -641,6 +642,14 @@ pvr_device_init(struct pvr_device *pvr_dev)
 	if (err)
 		return err;
 
+	/* Set any 'assigned-clocks' properties again. This is a workaround for
+	 * the clock handling on k3 platforms. There, one cannot set the clock
+	 * frequency until there is at least one (enabled) user if it.
+	 */
+	err = of_clk_set_defaults(drm_dev->dev->of_node, true);
+	if (err)
+		return err;
+
 	/* Map the control registers into memory. */
 	err = pvr_device_reg_init(pvr_dev);
 	if (err)
-- 
2.39.5