From: Sowjanya Komatineni <skomatineni@nvidia.com>
To: Dmitry Osipenko <digetx@gmail.com>,
Thierry Reding <thierry.reding@gmail.com>
Cc: <jonathanh@nvidia.com>, <frankc@nvidia.com>, <hverkuil@xs4all.nl>,
<sakari.ailus@iki.fi>, <robh+dt@kernel.org>,
<helen.koike@collabora.com>, <gregkh@linuxfoundation.org>,
<linux-media@vger.kernel.org>, <devicetree@vger.kernel.org>,
<linux-tegra@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v8 08/10] gpu: host1x: mipi: Keep MIPI clock enabled till calibration is done
Date: Wed, 5 Aug 2020 10:29:16 -0700 [thread overview]
Message-ID: <4689cfe9-e7c4-48bf-217f-3a31b59b8bda@nvidia.com> (raw)
In-Reply-To: <9ef0b875-e826-43e2-207e-168d2081ff6a@nvidia.com>
On 8/5/20 10:04 AM, Sowjanya Komatineni wrote:
>
> On 8/5/20 9:57 AM, Dmitry Osipenko wrote:
>> 05.08.2020 19:50, Sowjanya Komatineni пишет:
>>> On 8/5/20 9:47 AM, Dmitry Osipenko wrote:
>>>> 05.08.2020 19:33, Sowjanya Komatineni пишет:
>>>>> On 8/5/20 7:19 AM, Dmitry Osipenko wrote:
>>>>>> 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@gmail.com>
>>>>>>>>> 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)
>>>>>>>>> +{
>>>>>>>>> + 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?
>>>>> Confirmed with HW design team during this patch update.
>>>>>
>>>>> SW does not need to clear START bit and only write 1 takes effect to
>>>>> that bit.
>>>>>
>>>>> Also, no need to have delay or do any other register settings
>>>>> unclear as
>>>>> its FSM and there's nothing to get stuck.
>>>>>
>>>>> Also it goes thru small finite set of codes and by the time sensor
>>>>> programming happens for enabling streaming FSM will finish its
>>>>> calibration sequence much early and it will only wait for pads LP-11.
>>>>>
>>>>> So, during cancel we only need disable MIPI clock.
>>>>>
>>>> But there is no guarantee that cancel_calibration() couldn't be
>>>> invoked
>>>> in the middle of the calibration process, hence FSM could freeze in an
>>>> intermediate state if it's running on the disabled MIPI clock, this
>>>> doesn't sound good.
>>> Actual calibration logic uses UART_FST_CAL clock which is always
>>> enabled
>> What enables the UART_FST_CAL clock? I don't see this clock used
>> anywhere.
>
> UART_FST_MIPI_CAL is shared with uart and is always enabled all the time.
>
> I don't see mipi driver handling this and I think that's because this
> clock is enabled all the time as its used for UART as well. Probably
> thierry can comment on this clock.
>
> Also regarding cancel calibration, as FSM goes thru only finite
> sequence codes by the time csi stream and sensor stream happens which
> is where we check for calibration to complete for sure calibration
> will be finished and calibration logic will only wait for pads to be
> in LP-11 to apply results. So nothing special needed during cancel
> except to turn clock off to balance its usage count.
>
>
UART_FST_MIPI_CAL is the clock used for calibration logic which is FSM
that goes thru sequence codes and when done waits for pads to be in
LP-11 to apply results.
MIPI_CLK is controller gate clock which is also need to be kept enabled
as incase if it sees LP-11 it updates registers so its recommended to
have this clock enabled.
We can cancel_calibration() in CSI only when csi/sensor stream on fails
and in which case there will be no LP-11 so we can unconditionally
disable MIPI_CLK.
next prev parent reply other threads:[~2020-08-05 19:24 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 15:42 [PATCH v8 00/10] Support for Tegra video capture from external sensor Sowjanya Komatineni
2020-08-03 15:42 ` [PATCH v8 01/10] media: tegra-video: Fix channel format alignment Sowjanya Komatineni
2020-08-03 15:42 ` [PATCH v8 02/10] media: tegra-video: Enable TPG based on kernel config Sowjanya Komatineni
2020-08-03 15:42 ` [PATCH v8 03/10] media: tegra-video: Update format lookup to offset based Sowjanya Komatineni
2020-08-03 15:42 ` [PATCH v8 04/10] dt-bindings: tegra: Update VI and CSI bindings with port info Sowjanya Komatineni
2020-08-03 15:42 ` [PATCH v8 05/10] media: tegra-video: Separate CSI stream enable and disable implementations Sowjanya Komatineni
2020-08-03 15:42 ` [PATCH v8 06/10] media: tegra-video: Add support for external sensor capture Sowjanya Komatineni
2020-08-04 5:57 ` Dmitry Osipenko
2020-08-03 15:42 ` [PATCH v8 07/10] media: tegra-video: Add support for selection ioctl ops Sowjanya Komatineni
2020-08-03 15:42 ` [PATCH v8 08/10] gpu: host1x: mipi: Keep MIPI clock enabled till calibration is done Sowjanya Komatineni
2020-08-05 13:46 ` Thierry Reding
2020-08-05 14:05 ` Dmitry Osipenko
2020-08-05 14:19 ` Dmitry Osipenko
2020-08-05 16:33 ` Sowjanya Komatineni
2020-08-05 16:47 ` Dmitry Osipenko
2020-08-05 16:50 ` Sowjanya Komatineni
2020-08-05 16:57 ` Dmitry Osipenko
2020-08-05 17:04 ` Sowjanya Komatineni
2020-08-05 17:23 ` Dmitry Osipenko
2020-08-05 17:32 ` Sowjanya Komatineni
2020-08-05 17:29 ` Sowjanya Komatineni [this message]
2020-08-05 17:34 ` Dmitry Osipenko
2020-08-05 17:46 ` Sowjanya Komatineni
2020-08-05 18:06 ` Sowjanya Komatineni
2020-08-06 0:47 ` Sowjanya Komatineni
2020-08-06 13:32 ` Dmitry Osipenko
2020-08-06 15:59 ` Sowjanya Komatineni
2020-08-06 16:10 ` Dmitry Osipenko
2020-08-06 16:41 ` Sowjanya Komatineni
2020-08-06 16:45 ` Dmitry Osipenko
2020-08-06 16:51 ` Sowjanya Komatineni
2020-08-06 17:15 ` Dmitry Osipenko
2020-08-06 17:12 ` Sowjanya Komatineni
2020-08-06 17:27 ` Dmitry Osipenko
2020-08-06 17:44 ` Sowjanya Komatineni
2020-08-06 17:52 ` Sowjanya Komatineni
2020-08-06 18:01 ` Dmitry Osipenko
2020-08-06 18:07 ` Sowjanya Komatineni
2020-08-06 18:18 ` Dmitry Osipenko
2020-08-06 18:44 ` Sowjanya Komatineni
2020-08-06 18:51 ` Sowjanya Komatineni
2020-08-06 16:13 ` Dmitry Osipenko
2020-08-06 16:37 ` Dmitry Osipenko
2020-08-06 16:42 ` Sowjanya Komatineni
2020-08-06 16:43 ` Sowjanya Komatineni
2020-08-03 15:42 ` [PATCH v8 09/10] media: tegra-video: Add CSI MIPI pads calibration Sowjanya Komatineni
2020-08-03 15:42 ` [PATCH v8 10/10] media: tegra-video: Compute settle times based on the clock rate Sowjanya Komatineni
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