Re: [RFC PATCH v5 12/14] gpu: host1x: mipi: Keep MIPI clock enabled till calibration is done

[Sowjanya Komatineni]

On 7/28/20 4:03 AM, Dmitry Osipenko wrote:
> 27.07.2020 23:57, Sowjanya Komatineni ÐÐÑÐÑ:
> > With the split of MIPI calibration into tegra_mipi_calibrate() and
> > tegra_mipi_wait(), MIPI clock is not kept enabled till the calibration
> > is done.
> >
> > So, this patch skips disabling MIPI clock after triggering start of
> > calibration and disables it only after waiting for done status from
> > the calibration logic.
> >
> > This patch renames tegra_mipi_calibrate() as tegra_mipi_start_calibration()
> > and tegra_mipi_wait() as tegra_mipi_finish_calibration() to be inline
> > with their usage.
> >
> > As MIPI clock is left enabled and in case of any failures with CSI input
> > streaming tegra_mipi_finish_calibration() will not get invoked.
> > So added new API tegra_mipi_cancel_calibration() which disables MIPI clock
> > and consumer drivers can call this in such cases.
> >
> > Signed-off-by: Sowjanya Komatineni <skomatineni@xxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/tegra/dsi.c |  4 ++--
> >   drivers/gpu/host1x/mipi.c   | 19 ++++++++++---------
> >   include/linux/host1x.h      |  5 +++--
> >   3 files changed, 15 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/tegra/dsi.c b/drivers/gpu/drm/tegra/dsi.c
> > index 3820e8d..a7864e9 100644
> > --- a/drivers/gpu/drm/tegra/dsi.c
> > +++ b/drivers/gpu/drm/tegra/dsi.c
> > @@ -694,11 +694,11 @@ static int tegra_dsi_pad_calibrate(struct tegra_dsi *dsi)
> >   		DSI_PAD_PREEMP_PD(0x03) | DSI_PAD_PREEMP_PU(0x3);
> >   	tegra_dsi_writel(dsi, value, DSI_PAD_CONTROL_3);
> >   
> > -	err = tegra_mipi_calibrate(dsi->mipi);
> > +	err = tegra_mipi_start_calibration(dsi->mipi);
> >   	if (err < 0)
> >   		return err;
> >   
> > -	return tegra_mipi_wait(dsi->mipi);
> > +	return tegra_mipi_finish_calibration(dsi->mipi);
> >   }
> >   
> >   static void tegra_dsi_set_timeout(struct tegra_dsi *dsi, unsigned long bclk,
> > diff --git a/drivers/gpu/host1x/mipi.c b/drivers/gpu/host1x/mipi.c
> > index e606464..b15ab6e 100644
> > --- a/drivers/gpu/host1x/mipi.c
> > +++ b/drivers/gpu/host1x/mipi.c
> > @@ -293,17 +293,19 @@ int tegra_mipi_disable(struct tegra_mipi_device *dev)
> >   }
> >   EXPORT_SYMBOL(tegra_mipi_disable);
> >   
> > -int tegra_mipi_wait(struct tegra_mipi_device *device)
> > +void tegra_mipi_cancel_calibration(struct tegra_mipi_device *device)
> > +{
> Doesn't MIPI_CAL need to be reset here?
No need to reset MIPI CAL
> > +	clk_disable(device->mipi->clk);
> > +}
> > +EXPORT_SYMBOL(tegra_mipi_cancel_calibration);
> > +
> > +int tegra_mipi_finish_calibration(struct tegra_mipi_device *device)
> >   {
> >   	struct tegra_mipi *mipi = device->mipi;
> >   	void __iomem *status_reg = mipi->regs + (MIPI_CAL_STATUS << 2);
> >   	u32 value;
> >   	int err;
> >   
> > -	err = clk_enable(device->mipi->clk);
> > -	if (err < 0)
> > -		return err;
> > -
> >   	mutex_lock(&device->mipi->lock);
> >   
> >   	err = readl_relaxed_poll_timeout(status_reg, value,
> > @@ -315,9 +317,9 @@ int tegra_mipi_wait(struct tegra_mipi_device *device)
> >   
> >   	return err;
> >   }
> > -EXPORT_SYMBOL(tegra_mipi_wait);
> > +EXPORT_SYMBOL(tegra_mipi_finish_calibration);
> >   
> > -int tegra_mipi_calibrate(struct tegra_mipi_device *device)
> > +int tegra_mipi_start_calibration(struct tegra_mipi_device *device)
> >   {
> >   	const struct tegra_mipi_soc *soc = device->mipi->soc;
> >   	unsigned int i;
> > @@ -382,11 +384,10 @@ int tegra_mipi_calibrate(struct tegra_mipi_device *device)
> >   	tegra_mipi_writel(device->mipi, value, MIPI_CAL_CTRL);
> This function sets MIPI_CAL_CLKEN_OVR bit, does it mean that MIPI clock
> becomes always-ON?
>
> I don't see where MIPI_CAL_CLKEN_OVR is unset.

CLKEN_OVR was always kept enabled in the driver prior to my patch and I 
was not touching that.

But as we are turning ON/OFF MIPI clock itself no need to unset CLKEN_OVR

> >   	mutex_unlock(&device->mipi->lock);
> > -	clk_disable(device->mipi->clk);
> >   
> >   	return 0;
> >   }
> > -EXPORT_SYMBOL(tegra_mipi_calibrate);
> > +EXPORT_SYMBOL(tegra_mipi_start_calibration);
> >   
> >   static const struct tegra_mipi_pad tegra114_mipi_pads[] = {
> >   	{ .data = MIPI_CAL_CONFIG_CSIA },
> > diff --git a/include/linux/host1x.h b/include/linux/host1x.h
> > index 20c885d..b490dda 100644
> > --- a/include/linux/host1x.h
> > +++ b/include/linux/host1x.h
> > @@ -333,7 +333,8 @@ struct tegra_mipi_device *tegra_mipi_request(struct device *device,
> >   void tegra_mipi_free(struct tegra_mipi_device *device);
> >   int tegra_mipi_enable(struct tegra_mipi_device *device);
> >   int tegra_mipi_disable(struct tegra_mipi_device *device);
> > -int tegra_mipi_calibrate(struct tegra_mipi_device *device);
> > -int tegra_mipi_wait(struct tegra_mipi_device *device);
> > +int tegra_mipi_start_calibration(struct tegra_mipi_device *device);
> > +int tegra_mipi_finish_calibration(struct tegra_mipi_device *device);
> > +void tegra_mipi_cancel_calibration(struct tegra_mipi_device *device);
> >   
> >   #endif