linux-kernel - Re: [PATCH 5/9] arm64: dts: meson: g12a: add reset controller

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Date:   Fri, 15 Mar 2019 22:31:49 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Neil Armstrong <narmstrong@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>
Cc:     khilman@...libre.com, linux-amlogic@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 5/9] arm64: dts: meson: g12a: add reset controller

Hi Neil and Jerome,

On Thu, Mar 7, 2019 at 4:14 PM Neil Armstrong <narmstrong@...libre.com> wrote:
>
> From: Jerome Brunet <jbrunet@...libre.com>
>
> Add the reset controller device of g12a SoC family
>
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
>  arch/arm64/boot/dts/amlogic/meson-g12a.dtsi | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/amlogic/meson-g12a.dtsi b/arch/arm64/boot/dts/amlogic/meson-g12a.dtsi
> index f8f055c49f9a..2a700bb45d04 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-g12a.dtsi
> +++ b/arch/arm64/boot/dts/amlogic/meson-g12a.dtsi
> @@ -245,6 +245,13 @@
>                         #size-cells = <2>;
>                         ranges = <0x0 0x0 0x0 0xffd00000 0x0 0x100000>;
>
> +                       reset: reset-controller@...4 {
> +                               compatible = "amlogic,meson-g12a-reset",
> +                                            "amlogic,meson-axg-reset";
> +                               reg = <0x0 0x1004 0x0 0x9c>;
> +                               #reset-cells = <1>;
> +                       };
I tried to compare this with what is publicly available in
buildroot_openlinux_kernel_4.9_fbdev_20180706 - unfortunately this is
harder than I thought:
the buildroot kernel doesn't define the reset controller in mesong12a.dtsi

so I tried to follow the code in the HDMITX driver instead:
kernel/aml-4.9/drivers/amlogic/media/vout/hdmitx/hdmi_tx_20/hw/hw_txlx.c
uses P_RESET0_REGISTER and P_RESET2_REGISTER
these are defined in
kernel/aml-4.9/drivers/amlogic/media/vout/hdmitx/hdmi_tx_20/hw/txlx_reg.h
using:
> #define RESET_CBUS_REG_IDX 5
> #define BASE_REG_OFFSET 24
> #define RESET_CBUS_REG_ADDR(reg) \
>    ((RESET_CBUS_REG_IDX << BASE_REG_OFFSET) + (reg << 2))
>
> #define RESET0_REGISTER 0x01
> #define P_RESET0_REGISTER RESET_CBUS_REG_ADDR(RESET0_REGISTER)

when I do the maths:
(5 << 24) + (0x01 << 2) = 0x5000004

The GX SoCs have the reset controller at cbus + 0x4404
however, the offset may have changed in G12A because the SAR ADC
offset also changed (just one example).

Do you have any hint how to verify the CBUS offset (0x1004) of the
reset controller?


Regards
Martin