Messages in this thread | | | Date | Fri, 4 Nov 2022 23:53:57 +0530 | Subject | Re: [PATCH 1/3] arm64: dts: ti: k3-am65-main: drop RNG clock | From | Jayesh Choudhary <> |
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On 03/11/22 01:14, Nishanth Menon wrote: > On 12:04-20221102, Andrew Davis wrote: >> On 11/2/22 10:17 AM, Nishanth Menon wrote: >>> On 03:02-20221101, Jayesh Choudhary wrote: >>>> Drop RNG clock property as it is not controlled by rng-driver. >>> >>> Does'nt tell me what is the alternative? why is the hardware description >>> not sufficient for control? >>> >>> https://software-dl.ti.com/tisci/esd/latest/5_soc_doc/am65x_sr2/clocks.html#clocks-for-sa2-ul0-device >>> Looks like a perfectly valid description - do we have a bug and firmware >>> does'nt allow control here? >>> >> >> We have three input clocks feeding the SA2UL module, x1, x2, pka. PKA goes >> to the PKA sub-module (isn't it nice when they make things simple). But x1 and >> x2 are miscellaneous and bus clocks respectively and route to several sub-modules. >> >> All we drop here is the clock handle in the RNG sub-module, as that sub-module is >> not the owner of that clock (the parent SA2UL is). The alternative we could implement >> is to move the clock node up to the parent SA2UL node. >> >>>> >>>> Fixes: b366b2409c97 ("arm64: dts: ti: k3-am6: Add crypto accelarator node") >>>> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com> >>>> --- >>>> arch/arm64/boot/dts/ti/k3-am65-main.dtsi | 1 - >>>> 1 file changed, 1 deletion(-) >>>> >>>> diff --git a/arch/arm64/boot/dts/ti/k3-am65-main.dtsi b/arch/arm64/boot/dts/ti/k3-am65-main.dtsi >>>> index 4005a73cfea9..e166d7b7e3a1 100644 >>>> --- a/arch/arm64/boot/dts/ti/k3-am65-main.dtsi >>>> +++ b/arch/arm64/boot/dts/ti/k3-am65-main.dtsi >>>> @@ -126,7 +126,6 @@ rng: rng@4e10000 { >>>> compatible = "inside-secure,safexcel-eip76"; >>>> reg = <0x0 0x4e10000 0x0 0x7d>; >>>> interrupts = <GIC_SPI 24 IRQ_TYPE_LEVEL_HIGH>; >>>> - clocks = <&k3_clks 136 1>; >>> >>> Does this mean that the crypto module's power-domains property should be >>> dropped as well? >>> >> >> Why? the power-domains property is in the correct spot (up in the parent node). >> >> Now it is true we cant actually shut the SA2UL down since it is owned >> by the security processor, but since it is marked TI_SCI_PD_SHARED this >> should be fine. > > The idea of the descriptions were to describe what is controllable by > firmware, if there is no control due to the specified reason, it is a > device tree bug, and should be documented when dropping it. If it serves > a purpose in the firmware by indicating usage for example - it has valid > reason to stick around as it is expected to be used by firmware for some > specific reason.
The x1-clk to sa2ul is always running and fixed. What we can do is gate off the clock specific to trng module (x1-clk) by using TRNG_EN MMR to disable TRNG. Hence, uncontrollable.
> > The commit description does bring up the above mentioned questions and > must be explained appropriately. >
Okay, I will update the description properly in v2 for dropping this clock and for each patch (and not just in the cover-letter).
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