The "mediatek,mt8183-mali" compatible uses platform data that calls for
getting (and managing) two regulators ("mali" and "sram") but devfreq
does not support this usecase, resulting in DVFS not working.

Since a lot of MediaTek SoCs need to set the voltages for the GPU SRAM
regulator in a specific relation to the GPU VCORE regulator, a MediaTek
SoC specific driver was introduced to automatically satisfy, through
coupling, these constraints: this means that there is at all no need to
manage both regulators in panfrost but to otherwise just manage the main
"mali" (-> gpu vcore) regulator instead.

Keeping in mind that we cannot break the ABI, the most sensible route
(avoiding hacks and uselessly overcomplicated code) to get a MT8183
node with one power supply was to add a new "mediatek,mt8183b-mali"
compatible, which effectively deprecates the former.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
---
 drivers/gpu/drm/panfrost/panfrost_drv.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 45c4accb6a1e..4f39b410302c 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -647,6 +647,14 @@ static const struct panfrost_compatible amlogic_data = {
 	.vendor_quirk = panfrost_gpu_amlogic_quirk,
 };
 
+/*
+ * The old data with two power supplies for MT8183 is here only to
+ * keep retro-compatibility with older devicetrees, as DVFS will
+ * not work with this one.
+ *
+ * On new devicetrees please use the _b variant with a single and
+ * coupled regulators instead.
+ */
 static const char * const mediatek_mt8183_supplies[] = { "mali", "sram", NULL };
 static const char * const mediatek_mt8183_pm_domains[] = { "core0", "core1", "core2" };
 static const struct panfrost_compatible mediatek_mt8183_data = {
@@ -656,6 +664,14 @@ static const struct panfrost_compatible mediatek_mt8183_data = {
 	.pm_domain_names = mediatek_mt8183_pm_domains,
 };
 
+static const char * const mediatek_mt8183_b_supplies[] = { "mali", NULL };
+static const struct panfrost_compatible mediatek_mt8183_b_data = {
+	.num_supplies = ARRAY_SIZE(mediatek_mt8183_b_supplies) - 1,
+	.supply_names = mediatek_mt8183_b_supplies,
+	.num_pm_domains = ARRAY_SIZE(mediatek_mt8183_pm_domains),
+	.pm_domain_names = mediatek_mt8183_pm_domains,
+};
+
 static const char * const mediatek_mt8192_supplies[] = { "mali", NULL };
 static const char * const mediatek_mt8192_pm_domains[] = { "core0", "core1", "core2",
 							   "core3", "core4" };
@@ -684,6 +700,7 @@ static const struct of_device_id dt_match[] = {
 	{ .compatible = "arm,mali-bifrost", .data = &default_data, },
 	{ .compatible = "arm,mali-valhall-jm", .data = &default_data, },
 	{ .compatible = "mediatek,mt8183-mali", .data = &mediatek_mt8183_data },
+	{ .compatible = "mediatek,mt8183b-mali", .data = &mediatek_mt8183_b_data },
 	{ .compatible = "mediatek,mt8192-mali", .data = &mediatek_mt8192_data },
 	{}
 };
-- 
2.39.2