Re: [RFC PATCH v3 16/18] gpu: host1x: mipi: Split tegra_mipi_calibrate and tegra_mipi_wait

[Sowjanya Komatineni]

On 7/16/20 2:18 PM, Dmitry Osipenko wrote:
> 17.07.2020 00:09, Sowjanya Komatineni ÐÐÑÐÑ:
> > On 7/16/20 1:38 PM, Dmitry Osipenko wrote:
> > > 15.07.2020 07:20, Sowjanya Komatineni ÐÐÑÐÑ:
> > > > 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@xxxxxxxxxx>
> > > > ---
> > > ...
> > > >  Â int tegra_mipi_calibrate(struct tegra_mipi_device *device)
> > > >  Â {
> > > > @@ -370,12 +381,10 @@ int tegra_mipi_calibrate(struct
> > > > tegra_mipi_device *device)
> > > >  ÂÂÂÂÂ value |= MIPI_CAL_CTRL_START;
> > > >  ÂÂÂÂÂ tegra_mipi_writel(device->mipi, value, MIPI_CAL_CTRL);
> > > >  Â -ÂÂÂ 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
> > > >  ÂÂÂÂÂ mutex_unlock(&device->mipi->lock);
> > > >  ÂÂÂÂÂ clk_disable(device->mipi->clk);
> What keeps MIPI clock enabled after completion of the
> tegra_mipi_calibrate() invocation?

MIPI clock is disabled at end of tegra_mipi_calibrate and is re-enabled 
during tegra_mipi_wait.

I think I should fix this to keep the clock enabled till calibration 
results are latched.

All consumers of tegra_mipi_calibrate() will call tegra_mipi_wait().

So will remove clk_disable mipi clk at end of tegra_mipi_calibrate() and 
clk_enable mipi_clk at beginning of tegra_mipi_wait()

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