linux-kernel - Re: [PATCH 1/2] serial: qcom-geni: fix opp vote on shutdown

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Date:   Sat, 15 Jul 2023 11:19:39 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Rajendra Nayak <quic_rjendra@...cinc.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH 1/2] serial: qcom-geni: fix opp vote on shutdown

On 14.07.2023 17:08, Johan Hovold wrote:
> On Fri, Jul 14, 2023 at 04:29:08PM +0200, Konrad Dybcio wrote:
>> On 14.07.2023 15:02, Johan Hovold wrote:
>>> The operating-performance-point vote needs to be dropped when shutting
>>> down the port to avoid wasting power by keeping resources like power
>>> domains in an unnecessarily high performance state (e.g. when a UART
>>> connected Bluetooth controller is not in use).
>>>
>>> Fixes: a5819b548af0 ("tty: serial: qcom_geni_serial: Use OPP API to set clk/perf state")
>>> Cc: stable@...r.kernel.org      # 5.9
>>> Cc: Rajendra Nayak <quic_rjendra@...cinc.com>
>>> Cc: Matthias Kaehlcke <mka@...omium.org>
>>> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
>>> ---
>> I don't know a whole lot about this subsystem, but the PM call has
>> a pointer to uport which already contains this clock rate.. Is it
>> zeroed out by the core before we reach it, which would prevent us
>> from reusing it?
> 
> No, but this driver has other issues and I couldn't be arsed fixing them
> before addressing this bug.
> 
> Specifically that uartclk variable can currently be set by userspace...
> 
> I'll fix that up next week.
OK sounds good

Acked-by: Konrad Dybcio <konrad.dybcio@...aro.org>

Konrad
> 
> Johan