Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20220113115745.45826-1-liang.yang@amlogic.com>
 <20220113115745.45826-4-liang.yang@amlogic.com> <20220113212957.768FFC36AE3@smtp.kernel.org>
 <5d99ac02-a246-5bcc-2ecb-371b0d193537@amlogic.com>
In-Reply-To: <5d99ac02-a246-5bcc-2ecb-371b0d193537@amlogic.com>
From:   Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Date:   Sat, 15 Jan 2022 01:09:11 +0100
Message-ID: <CAFBinCDkNk+Ba340vshhL2rE76U9qb_dZ5ZsgWnMgFYpL6i1jA@mail.gmail.com>
Subject: Re: [PATCH v9 3/4] clk: meson: add DT documentation for emmc clock controller
To:     Liang Yang <liang.yang@amlogic.com>
Cc:     Stephen Boyd <sboyd@kernel.org>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Kevin Hilman <khilman@baylibre.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Rob Herring <robh+dt@kernel.org>, linux-clk@vger.kernel.org,
        Jianxin Pan <jianxin.pan@amlogic.com>,
        Victor Wan <victor.wan@amlogic.com>,
        XianWei Zhao <xianwei.zhao@amlogic.com>,
        Kelvin Zhang <kelvin.zhang@amlogic.com>,
        BiChao Zheng <bichao.zheng@amlogic.com>,
        YongHui Yu <yonghui.yu@amlogic.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Liang,

On Fri, Jan 14, 2022 at 4:06 AM Liang Yang <liang.yang@amlogic.com> wrote:
[...]
> >> +properties:
> >> +  compatible:
> >> +    enum:
> >> +      - "amlogic,axg-mmc-clkc", "syscon"
> >
> > Why is it a syscon?
>
> The register documented by reg is shared with SD/eMMC controller port C,
> and it need to be ops on NFC driver.
Can you please share an example how the .dts would look like in the
end for two example cases:
1) using the sd_emmc_c MMC interface
2) not using the MMC interface of sd_emmc_c but only using it's clocks
for the NFC

Initially I wanted to suggest the usage of a sub-node with compatible
= "mmc-slot" (see
Documentation/devicetree/bindings/mmc/amlogic,meson-mx-sdio.txt for an
example) to decide whether the MMC controller is registered or whether
just the clock controller is registered.
However, the mmc-slot compatible string is not documented in
Documentation/devicetree/bindings/mmc/mmc-controller.yaml currently.
Maybe the MMC maintainers have any suggestions if other IPs have
similar requirements (for IPs with shared parts).


Best regards,
Martin