Commit 2317b87a2a6f ("arm64: dts: qcom: db820c: Add vdd_gfx and tie it into mmcc")
introduced this voltage regulator which seems to be essential for the GPU,
according to the board schematics [0]. The problem is that such commit sets
the regulator min/max voltage range to a static value, which is a bit lower than
the range supported to such regulator [1]. With that, the GPU is not stable
as per my experiments (in a Dragonboard 820c-based board) - I've observed
sudden reboots into a FW bad state.
More than that, my experiment showed that this regulator must be set to
always-on - this idea came from a commit in Linaro's tree, from Rajendra [2].
With the voltage range updated plus set as always-on, the GPU is working
correctly, in a stable fashion.
[0] See page 9 (VDD_GFX), at
https://www.96boards.org/documentation/consumer/dragonboard/dragonboard820c/hardware-docs/files/db820c-schematics.pdf
[1] See section 3.5.3 (FT-SMPS) in the "PMI8994/PMI8996 Power Management IC",
at https://developer.qualcomm.com/download/sd820e/pmi8994pmi8996-power-management-ic-device-specification.pdf
[2] https://git.linaro.org/landing-teams/working/qualcomm/kernel.git/commit/?h=release/qcomlt-4.14&id=75fb43f3a62
Cc: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>
Cc: Vinod Koul <vkoul@xxxxxxxxxx>
Fixes: 2317b87a2a6f ("arm64: dts: qcom: db820c: Add vdd_gfx and tie it into mmcc")
Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
---
Hi Andy/Bjorn/all, this patch was tested in 5.14, but I've tested it
in the linux-next tree as well and was able to apply there cleanly.
I'm new in the DTS world, so my apologies in advance for any rookie
mistake - suggestions are appreciated! Thanks in advance for the review,
Guilherme
arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi b/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi
index 51e17094d7b1..977842068619 100644
--- a/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi
+++ b/arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi
@@ -699,8 +699,11 @@ &pmi8994_spmi_regulators {
vdd_gfx: s2@1700 {
reg = <0x1700 0x100>;
regulator-name = "VDD_GFX";
- regulator-min-microvolt = <980000>;
- regulator-max-microvolt = <980000>;
+ regulator-min-microvolt = <350000>;
+ regulator-max-microvolt = <1350000>;
+ regulator-always-on;
+ status = "okay";
+
};
};
--
2.33.0
