linux-kernel - Re: [RFC PATCH v3 16/18] gpu: host1x: mipi: Split tegra_mipi_calibrate and tegra_mipi

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Message-ID: <c4945c77-5de1-e9b1-9f4f-cdd78bca18c7@gmail.com>
Date:   Fri, 17 Jul 2020 00:18:39 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, frankc@...dia.com,
        hverkuil@...all.nl, sakari.ailus@....fi, robh+dt@...nel.org,
        helen.koike@...labora.com
Cc:     sboyd@...nel.org, gregkh@...uxfoundation.org,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org
Subject: Re: [RFC PATCH v3 16/18] gpu: host1x: mipi: Split
 tegra_mipi_calibrate and tegra_mipi_wait

17.07.2020 00:09, Sowjanya Komatineni пишет:
> 
> On 7/16/20 1:38 PM, Dmitry Osipenko wrote:
>> 15.07.2020 07:20, Sowjanya Komatineni пишет:
>>> SW can trigger MIPI pads calibration any time after power on
>>> but calibration results will be latched and applied to the pads
>>> by MIPI CAL unit only when the link is in LP-11 state and then
>>> status register will be updated.
>>>
>>> For CSI, trigger of pads calibration happen during CSI stream
>>> enable where CSI receiver is kept ready prior to sensor or CSI
>>> transmitter stream start.
>>>
>>> So, pads may not be in LP-11 at this time and waiting for the
>>> calibration to be done immediate after calibration start will
>>> result in timeout.
>>>
>>> This patch splits tegra_mipi_calibrate() and tegra_mipi_wait()
>>> so triggering for calibration and waiting for it to complete can
>>> happen at different stages.
>>>
>>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>>> ---
>> ...
>>>   int tegra_mipi_calibrate(struct tegra_mipi_device *device)
>>>   {
>>> @@ -370,12 +381,10 @@ int tegra_mipi_calibrate(struct
>>> tegra_mipi_device *device)
>>>       value |= MIPI_CAL_CTRL_START;
>>>       tegra_mipi_writel(device->mipi, value, MIPI_CAL_CTRL);
>>>   -    err = tegra_mipi_wait(device->mipi);
>> Doesn't MIPI clock need to be enabled during of the calibration process?
> MIPI clock is already enabled in tegra_mipi_calibrate
>>
>>>       mutex_unlock(&device->mipi->lock);
>>>       clk_disable(device->mipi->clk);

What keeps MIPI clock enabled after completion of the
tegra_mipi_calibrate() invocation?

>>>   -    return err;
>>> +    return 0;
>>>   }
>>>   EXPORT_SYMBOL(tegra_mipi_calibrate);