From: Giulio Benetti <giulio.benetti@benettiengineering.com>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Jernej Skrabec <jernej.skrabec@siol.net>,
airlied@linux.ie, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, wens@csie.org,
linux-arm-kernel@lists.infradead.org, treding@nvidia.com,
Giulio Benetti <giulio.benetti@micronovasrl.com>,
Marjan Pascolo <marjan.pascolo@trexom.it>
Subject: Re: [PATCH v2 2/2] drm/sun4i: tcon: improve DCLK polarity handling
Date: Mon, 11 Jan 2021 18:37:42 +0100 [thread overview]
Message-ID: <fc01c99c-3b5d-0064-917f-1582abba51f4@benettiengineering.com> (raw)
In-Reply-To: <20210111172052.7v522xam74xkq6se@gilmour>
On 1/11/21 6:20 PM, Maxime Ripard wrote:
> On Fri, Jan 08, 2021 at 03:34:52PM +0100, Giulio Benetti wrote:
>> Hi,
>>
>> On 1/8/21 10:23 AM, Maxime Ripard wrote:
>>> Hi,
>>>
>>> Thanks for those patches
>>>
>>> On Thu, Jan 07, 2021 at 03:30:32AM +0100, Giulio Benetti wrote:
>>>> From: Giulio Benetti <giulio.benetti@micronovasrl.com>
>>>>
>>>> It turned out(Maxime suggestion) that bit 26 of SUN4I_TCON0_IO_POL_REG is
>>>> dedicated to invert DCLK polarity and this makes thing really easier than
>>>> before. So let's handle DCLK polarity by adding
>>>> SUN4I_TCON0_IO_POL_DCLK_POSITIVE as bit 26 and activating according to
>>>> bus_flags the same way is done for all the other signals.
>>>>
>>>> Cc: Maxime Ripard <maxime@cerno.tech>
>>>
>>> Suggested-by would be nice here :)
>>
>> Ok, didn't know about this tag
>>
>>>> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
>>>> ---
>>>> drivers/gpu/drm/sun4i/sun4i_tcon.c | 20 +-------------------
>>>> drivers/gpu/drm/sun4i/sun4i_tcon.h | 1 +
>>>> 2 files changed, 2 insertions(+), 19 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
>>>> index 52598bb0fb0b..30171ccd87e5 100644
>>>> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
>>>> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
>>>> @@ -569,26 +569,8 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
>>>> if (info->bus_flags & DRM_BUS_FLAG_DE_LOW)
>>>> val |= SUN4I_TCON0_IO_POL_DE_NEGATIVE;
>>>> - /*
>>>> - * On A20 and similar SoCs, the only way to achieve Positive Edge
>>>> - * (Rising Edge), is setting dclk clock phase to 2/3(240°).
>>>> - * By default TCON works in Negative Edge(Falling Edge),
>>>> - * this is why phase is set to 0 in that case.
>>>> - * Unfortunately there's no way to logically invert dclk through
>>>> - * IO_POL register.
>>>> - * The only acceptable way to work, triple checked with scope,
>>>> - * is using clock phase set to 0° for Negative Edge and set to 240°
>>>> - * for Positive Edge.
>>>> - * On A33 and similar SoCs there would be a 90° phase option,
>>>> - * but it divides also dclk by 2.
>>>> - * Following code is a way to avoid quirks all around TCON
>>>> - * and DOTCLOCK drivers.
>>>> - */
>>>> if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_POSEDGE)
>>>> - clk_set_phase(tcon->dclk, 0);
>>>> -
>>>> - if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
>>>> - clk_set_phase(tcon->dclk, 240);
>>>> + val |= SUN4I_TCON0_IO_POL_DCLK_POSITIVE;
>>>
>>> I'm not really sure why we need the first patch of this series here?
>>
>> The idea was to have 2 for testing, 1st one is already applicable, while the
>> other must be tested, but I can send only one with no problem.
>>
>>> That patch only seem to undo what you did in patch 1
>>
>> No, it doesn't, the 2nd one change the way it achieve the same thing,
>> because the 1st swap DCLK phase, while the 2nd uses the IO_POL bit to set IO
>> polarity according to bus_flags.
>
> It makes sense for testing, but I'm not sure we want to carry it into
> the history. Can you squash them both into the same patch?
Sure, I'm going to send V3 then.
Thank you
Best regards
--
Giulio Benetti
Benetti Engineering sas
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next prev parent reply other threads:[~2021-01-12 7:58 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-06 19:27 [PATCH 0/2] drm/sun4i: fix DCLK and improve its handling Giulio Benetti
2021-01-06 19:27 ` [PATCH 1/2] drm/sun4i: tcon: fix inverted DCLK polarity Giulio Benetti
2021-01-06 21:00 ` Jernej Škrabec
2021-01-07 2:30 ` [PATCH v2 0/2] drm/sun4i: fix DCLK and improve its handling Giulio Benetti
2021-01-07 2:30 ` [PATCH v2 1/2] drm/sun4i: tcon: fix inverted DCLK polarity Giulio Benetti
2021-01-07 2:30 ` [PATCH v2 2/2] drm/sun4i: tcon: improve DCLK polarity handling Giulio Benetti
2021-01-08 9:23 ` Maxime Ripard
2021-01-08 9:32 ` Marjan Pascolo
2021-01-08 14:46 ` Giulio Benetti
2021-01-08 14:34 ` Giulio Benetti
2021-01-11 17:20 ` Maxime Ripard
2021-01-11 17:37 ` Giulio Benetti [this message]
2021-01-11 17:46 ` [PATCH v3] drm/sun4i: tcon: fix inverted DCLK polarity Giulio Benetti
2021-01-13 9:42 ` Maxime Ripard
2021-01-13 10:47 ` [PATCH v4] " Giulio Benetti
2021-01-13 16:05 ` [PATCH v5] " Giulio Benetti
2021-01-14 1:32 ` kernel test robot
2021-01-14 7:58 ` Marjan Pascolo
2021-01-14 8:12 ` Giulio Benetti
2021-01-14 8:17 ` [PATCH v6] " Giulio Benetti
2021-01-14 11:40 ` Marjan Pascolo
2021-01-14 11:42 ` Maxime Ripard
2021-02-10 16:22 ` [PATCH] pinctrl/sunxi: adding input-debounce-ns property Marjan Pascolo
2021-02-17 11:03 ` Maxime Ripard
2021-02-26 12:53 ` Marjan Pascolo
2021-03-04 15:51 ` Maxime Ripard
2021-01-13 10:48 ` [PATCH v3] drm/sun4i: tcon: fix inverted DCLK polarity Giulio Benetti
2021-01-06 19:28 ` [PATCH 2/2] drm/sun4i: tcon: improve DCLK polarity handling Giulio Benetti
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