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Subject: Re: [RFC PATCH v5 12/14] gpu: host1x: mipi: Keep MIPI clock enabled
 till calibration is done
To:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        thierry.reding@gmail.com, jonathanh@nvidia.com, frankc@nvidia.com,
        hverkuil@xs4all.nl, sakari.ailus@iki.fi, robh+dt@kernel.org,
        helen.koike@collabora.com
Cc:     sboyd@kernel.org, gregkh@linuxfoundation.org,
        linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-i2c@vger.kernel.org
References: <1595883452-17343-1-git-send-email-skomatineni@nvidia.com>
 <1595883452-17343-13-git-send-email-skomatineni@nvidia.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <b21e3227-d0d8-5b4a-ae69-aa29551a22c3@gmail.com>
Date:   Tue, 28 Jul 2020 14:03:54 +0300
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27.07.2020 23:57, Sowjanya Komatineni пишет:
> 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@nvidia.com>
> ---
>  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?

> +	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.

>  	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
>