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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Wed, 8 Mar 2017 12:38:44 +0100
Message-ID: <CAMuHMdVRa3C4ikaoNDDU21NbRVcPTf0z6fPiJ1nF-VDd+3Dm0g@mail.gmail.com>
Subject: Re: [PATCH] clk: tegra: mark TEGRA210_CLK_DBGAPB as always on
To: Jon Hunter <jonathanh@nvidia.com>
Cc: Peter De Schrijver <pdeschrijver@nvidia.com>,
        Prashant Gaikwad <pgaikwad@nvidia.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@codeaurora.org>,
        Stephen Warren <swarren@wwwdotorg.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Alexandre Courbot <gnurou@gmail.com>,
        linux-clk <linux-clk@vger.kernel.org>, linux-tegra@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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Hi Jon,

On Wed, Mar 8, 2017 at 11:13 AM, Jon Hunter <jonathanh@nvidia.com> wrote:
>> I had a similar issue with SH-Mobile AG5, where the power domain containing
>> the JTAG interface is powered down.
>
> This reminds me, does your patch assume that the DFD power domain is
> enabled? I am guessing that it needs to be for JTAG to work.

Yes. The pm-rmobile driver looks for "arm,coresight-etm3x" devices, and
marks the corresponding PM Domain as always-on, as long as the
Coresight code doesn't handle runtime PM.

For R-Mobile A1 and APE6 I already have added such device nodes, as any access
to a debug register hangs when the debug power domain is powered down.
For SH-Mobile AG5, I hadn't, as the debug power domain needs to be powered
for JTAG functionality only.

For the latter, perhaps we also need a command line parameter to change
a device status from "disabled" to "enabled"?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds