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

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Message-ID: <20d63eca-4b2b-584e-a391-a4fb64a16b40@nvidia.com>
Date:   Thu, 16 Jul 2020 14:09:36 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.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


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