From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Alexander Stein <alexander.stein@ew.tq-group.com>,
Andrzej Hajda <andrzej.hajda@intel.com>,
Neil Armstrong <neil.armstrong@linaro.org>,
Robert Foss <robert.foss@linaro.org>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
Jonas Karlman <jonas@kwiboo.se>,
Jernej Skrabec <jernej.skrabec@gmail.com>,
David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc: Marek Vasut <marex@denx.de>,
Frieder Schrempf <frieder.schrempf@kontron.de>,
dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: drm/bridge: ti-sn65dsi83: Add enable delay property
Date: Fri, 9 Dec 2022 10:07:45 +0100 [thread overview]
Message-ID: <e1844fdc-c640-747d-e38f-400669f2a1a8@linaro.org> (raw)
In-Reply-To: <7463917.EvYhyI6sBW@steina-w>
On 09/12/2022 09:54, Alexander Stein wrote:
> Hello Krzysztof,
>
> thanks for the fast feedback.
>
> Am Freitag, 9. Dezember 2022, 09:39:49 CET schrieb Krzysztof Kozlowski:
>> On 09/12/2022 09:33, Alexander Stein wrote:
>>> It takes some time until the enable GPIO has settled when turning on.
>>> This delay is platform specific and may be caused by e.g. voltage
>>> shifts, capacitors etc.
>>>
>>> Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
>>> ---
>>>
>>> .../devicetree/bindings/display/bridge/ti,sn65dsi83.yaml | 4 ++++
>>> 1 file changed, 4 insertions(+)
>>>
>>> diff --git
>>> a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
>>> b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
>>> index 48a97bb3e2e0d..3f50d497cf8ac 100644
>>> --- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
>>> +++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
>>>
>>> @@ -32,6 +32,10 @@ properties:
>>> maxItems: 1
>>> description: GPIO specifier for bridge_en pin (active high).
>>>
>>> + ti,enable-delay-us:
>>> + default: 10000
>>> + description: Enable time delay for enable-gpios
>>
>> Aren't you now mixing two separate delays? One for entire block on (I
>> would assume mostly fixed delay) and one depending on regulators
>> (regulator-ramp-delay, regulator-enable-ramp-delay). Maybe you miss the
>> second delays in your power supply? If so, the first one might be fixed
>> and hard-coded in the driver?
>
> Apparently there are two different delays: reset time (t_reset) of 10ms as
> specified by datasheet. This is already ensured by a following delay after
> requesting enable_gpio as low and switching the GPIO to low in disable path.
>
> When enabling this GPIO it takes some time until it is valid on the chip, this
> is what this series is about. It's highly platform specific.
>
> Unfortunately this is completely unrelated to the vcc-supply regulator. This
> one has to be enabled before the enable GPIO can be enabled. So there is no
> regulator-ramp-delay.
Your driver does one after another - regulator followed immediately by
gpio - so this as well can be a delay from regulator (maybe not ramp but
enable delay).
Best regards,
Krzysztof
next prev parent reply other threads:[~2022-12-09 9:07 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-09 8:33 [PATCH 0/2] TI SN65DSI83 GPIO enable delay support Alexander Stein
2022-12-09 8:33 ` [PATCH 1/2] dt-bindings: drm/bridge: ti-sn65dsi83: Add enable delay property Alexander Stein
2022-12-09 8:39 ` Krzysztof Kozlowski
2022-12-09 8:54 ` Alexander Stein
2022-12-09 9:07 ` Krzysztof Kozlowski [this message]
2022-12-09 9:36 ` Alexander Stein
2022-12-09 9:50 ` Krzysztof Kozlowski
2022-12-09 9:51 ` Krzysztof Kozlowski
2022-12-09 12:02 ` Marek Vasut
2022-12-09 12:10 ` Krzysztof Kozlowski
2022-12-09 12:23 ` Alexander Stein
2022-12-09 12:21 ` Alexander Stein
2022-12-09 12:43 ` Marek Vasut
2022-12-09 13:38 ` Alexander Stein
2022-12-09 14:49 ` Marek Vasut
2022-12-12 9:09 ` Frieder Schrempf
2022-12-12 9:23 ` Krzysztof Kozlowski
2022-12-12 12:29 ` Frieder Schrempf
2022-12-12 12:50 ` Marek Vasut
2022-12-12 9:32 ` Laurent Pinchart
2022-12-12 11:49 ` Frieder Schrempf
2022-12-12 12:05 ` Laurent Pinchart
2022-12-11 18:50 ` Laurent Pinchart
2022-12-09 8:33 ` [PATCH 2/2] drm: bridge: ti-sn65dsi83: Add enable delay support Alexander Stein
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