Re: [PATCH v4 12/19] arm64: dts: mediatek: mt8192-asurada: Couple VGPU and VSRAM_OTHER regulators
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From: Chen-Yu Tsai <wenst@chromium.org>
Date: 2023-03-07 09:45:04
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On Tue, Mar 7, 2023 at 5:30 PM AngeloGioacchino Del Regno [off-list ref] wrote:
Il 07/03/23 10:24, Chen-Yu Tsai ha scritto:quoted
On Fri, Mar 3, 2023 at 12:09 PM Chen-Yu Tsai [off-list ref] wrote:quoted
On Thu, Mar 2, 2023 at 6:17 PM AngeloGioacchino Del Regno [off-list ref] wrote:quoted
Il 02/03/23 11:03, Chen-Yu Tsai ha scritto:quoted
On Wed, Mar 1, 2023 at 5:55 PM AngeloGioacchino Del Regno [off-list ref] wrote:quoted
Add coupling for these regulators, as VSRAM_OTHER is used to power the GPU SRAM, and they have a strict voltage output relation to satisfy in order to ensure GPU stable operation. While at it, also add voltage constraint overrides for the GPU SRAM regulator "mt6359_vsram_others" so that we stay in a safe range of 0.75-0.80V. Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> --- arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi | 9 +++++++++ 1 file changed, 9 insertions(+)diff --git a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi index 8570b78c04a4..f858eca219d7 100644 --- a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi +++ b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi@@ -447,6 +447,13 @@ &mt6359_vrf12_ldo_reg { regulator-always-on; }; +&mt6359_vsram_others_ldo_reg { + regulator-min-microvolt = <750000>; + regulator-max-microvolt = <800000>; + regulator-coupled-with = <&mt6315_7_vbuck1>; + regulator-coupled-max-spread = <10000>;Looking again at the downstream OPP table, it seems there's no voltage difference requirement. It only needs V_SRAM >= V_GPU. Same applies to MT8195. Looks like only MT8183 and MT8186 need V_SRAM - V_GPU >= 10000.On MT8195 we don't need any regulator coupling. There, the GPU-SRAM voltage is fixed at .. I don't remember, 0.7V? - anyway - MT8195 doesn't need to scale the vsram.Looks like it's fixed at 0.75V. I guess we're Ok on MT8195.quoted
quoted
Would setting max-spread to 0 work? I ask because with both regulator's maximum voltage set to 0.8V, there's no way we can reach the highest OPP.No that doesn't work. I can raise the Vgpu max voltage to 0.88V to solve the issue right here and right now, or we can leave it like that and revisit it later. I would at this point go for setting mt6315_7_vbuck1's max-microvolt to 880000, as this is the maximum recommended voltage for the GPU as per the MT8192 datasheet, it would also make sense as we would be still describing the hardware in a correct manner. What do you think?If it's just to accommodate the coupler stuff, I say just set the maximum at the lowest possible setting that satisfies the coupler constraint and granularity of the regulator. The regulator does 6250 uV steps, so I guess we could set the maximum at 812500 uV, with a comment stating the nominal voltage of 800000 uV and that the extra 12500 uV is to workaround coupler limitations. Does that sound OK?Even without changing anything, the coupler seems to work OK: vsram_others 1 1 0 normal 800mV 0mA 750mV 800mV 10006000.syscon:power-controller-domain 1 0mA 0mV 0mV Vgpu 2 2 0 normal 800mV 0mA 606mV 800mV 13000000.gpu-mali 1 0mA 800mV 800mV 10006000.syscon:power-controller-domain 1 0mA 0mV 0mV Am I missing something?I don't think you are... I may be getting confused by all of the changesets that I'm pushing at once. Hence, is this commit fine as it is?
It works for some reason. Maybe it's a bug in the coupler. Either way I think it works, even though the numbers might be a bit off. We can revisit it later. Reviewed-by: Chen-Yu Tsai <wenst@chromium.org> _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel