linux-kernel - Re: [PATCH v8 08/10] gpu: host1x: mipi: Keep MIPI clock enabled till calibration is done

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Message-ID: <0e78c5ca-c529-1e98-891d-30351c9aae81@gmail.com>
Date:   Wed, 5 Aug 2020 20:34:22 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>
Cc:     jonathanh@...dia.com, frankc@...dia.com, hverkuil@...all.nl,
        sakari.ailus@....fi, robh+dt@...nel.org, helen.koike@...labora.com,
        gregkh@...uxfoundation.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 08/10] gpu: host1x: mipi: Keep MIPI clock enabled till
 calibration is done

05.08.2020 20:29, Sowjanya Komatineni пишет:
...
> UART_FST_MIPI_CAL is the clock used for calibration logic which is FSM
> that goes thru sequence codes and when done waits for pads to be in
> LP-11 to apply results.
> 
> MIPI_CLK is controller gate clock which is also need to be kept enabled
> as incase if it sees LP-11 it updates registers so its recommended to
> have this clock enabled.
> 
> We can cancel_calibration() in CSI only when csi/sensor stream on fails
> and in which case there will be no LP-11 so we can unconditionally
> disable MIPI_CLK.
> 

There is no guarantee that the fail comes before the LP-11. For example,
some odd camera driver may have a complicated enable sequence which may
fail after enabling the hardware streaming.