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

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Date:   Thu, 16 Jul 2020 23:38:27 +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

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?

>  	mutex_unlock(&device->mipi->lock);
>  	clk_disable(device->mipi->clk);
>  
> -	return err;
> +	return 0;
>  }
>  EXPORT_SYMBOL(tegra_mipi_calibrate);