05.08.2020 17:05, Dmitry Osipenko пишет:
> 05.08.2020 16:46, Thierry Reding пишет:
>> On Mon, Aug 03, 2020 at 08:42:24AM -0700, Sowjanya Komatineni wrote:
>>> 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.
>>>
>>> Reviewed-by: Dmitry Osipenko <digetx@xxxxxxxxx>
>>> 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)
>>> +{
>>> + clk_disable(device->mipi->clk);
>>
>> Do we need to do anything with the MIPI_CAL_CTRL and MIPI_CAL_STATUS
>> registers here? We don't clear the START bit in the former when the
>> calibration has successfully finished, but I suspect that's because
>> the bit is self-clearing. But I wonder if we still need to clear it
>> upon cancellation to make sure the calibration does indeed stop.
>
> Apparently there is no way to explicitly stop calibration other than to
> reset MIPI calibration block, but Sowjanya says this is unnecessary.
>
> Perhaps having a fixed delay before disabling clock could be enough to
> ensure that calibration is stopped before the clock is disabled?
>
Actually, there is a MIPI_CAL_ACTIVE bit in the status register. Maybe
it needs to be polled until it's unset?
