From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Andrey Gusakov <andrey.gusakov@cogentembedded.com>,
Jyri Sarha <jsarha@ti.com>,
dri-devel@lists.freedesktop.org,
Peter Ujfalusi <peter.ujfalusi@ti.com>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
Chris Healy <cphealy@gmail.com>
Subject: Re: [21/21] drm/bridge: tc358767: implement naive HPD handling
Date: Wed, 20 Mar 2019 08:57:38 +0200 [thread overview]
Message-ID: <49ff451d-9d95-d4c7-e749-72bb9dbf7365@ti.com> (raw)
In-Reply-To: <20190319181825.15146-1-andrew.smirnov@gmail.com>
On 19/03/2019 20:18, Andrey Smirnov wrote:
> TC358767 has two GPIO pins that can be used for HPD signal. I think
> instead of hardcoding GPIO0 here it would be more flexible to expose
> boths gpios as a gpiochip and use gpiolib API to query the value of
> HPD as well as use "hpd-gpios" binidng in DT to select which input to
> use.
>
> Another argument in favour of this solution is that Toshiba's FAEs (at
> least some) recommend thier customers to connect HPD signal to SoC's
> GPIOs and bypass TC358767 entirely. Their reasoning being that
> TC358767 implements a generic GPIO contoller and there's no advantage
> in going through TC358767 if you could use your "normal" GPIOs.
>
> Using gpiolib API would allow us to handle both usecase with the same
> code.
>
> Lastly, by treating "hpd-gpios" as an optional property, we can
> preserve old driver behaviour regardless if it is connected to DP or
> eDP panel. Not saying that this is really worth doing, just pointing
> out that this option would be on the table as well.
I think that's a good point.
There's one thing that TC358767 offers, which may not be available on
most generic GPIO controllers, though: it can detect short (programmable
length) pulses, thus it's possible to easily implement the DisplayPort
IRQ mechanism. I'm not sure if it's possible to implement reliable DP
IRQ detection without HW support.
Still, I think using standard gpios makes sense.
Tomi
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next prev parent reply other threads:[~2019-03-20 6:57 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-19 10:40 [PATCH 00/21] drm/bridge: tc358767: DP support Tomi Valkeinen
2019-03-19 10:40 ` [PATCH 01/21] drm/bridge: tc358767: fix tc_aux_get_status error handling Tomi Valkeinen
2019-03-19 10:40 ` [PATCH 02/21] drm/bridge: tc358767: reset voltage-swing & pre-emphasis Tomi Valkeinen
2019-03-19 10:40 ` [PATCH 03/21] drm/bridge: tc358767: fix ansi 8b10b use Tomi Valkeinen
2019-03-19 10:40 ` [PATCH 04/21] drm/bridge: tc358767: cleanup spread & scrambler_dis Tomi Valkeinen
2019-03-19 10:40 ` [PATCH 05/21] drm/bridge: tc358767: remove unused swing & preemp Tomi Valkeinen
2019-03-19 10:40 ` [PATCH 06/21] drm/bridge: tc358767: cleanup aux_link_setup Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 07/21] drm/bridge: tc358767: move video stream setup to tc_main_link_stream Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 08/21] drm/bridge: tc358767: split stream enable/disable Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 09/21] drm/bridge: tc358767: move PXL PLL enable/disable to " Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 10/21] drm/bridge: tc358767: add link disable function Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 11/21] drm/bridge: tc358767: ensure DP is disabled before LT Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 12/21] drm/bridge: tc358767: remove unnecessary msleep Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 13/21] drm/bridge: tc358767: use more reliable seq when finishing LT Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 14/21] drm/bridge: tc358767: cleanup LT result check Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 15/21] drm/bridge: tc358767: clean-up link training Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 16/21] drm/bridge: tc358767: remove check for video mode in link enable Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 17/21] drm/bridge: tc358767: use bridge mode_valid Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 18/21] drm/bridge: tc358767: remove tc_connector_best_encoder Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 19/21] drm/bridge: tc358767: copy the mode data, instead of storing the pointer Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 20/21] drm/bridge: tc358767: add GPIO & interrupt registers Tomi Valkeinen
2019-03-19 10:41 ` [PATCH 21/21] drm/bridge: tc358767: implement naive HPD handling Tomi Valkeinen
2019-03-19 18:18 ` [21/21] " Andrey Smirnov
2019-03-20 5:55 ` Andrey Smirnov
2019-03-20 7:06 ` Tomi Valkeinen
2019-03-20 6:57 ` Tomi Valkeinen [this message]
2019-03-20 13:03 ` Tomi Valkeinen
2019-03-20 22:58 ` Andrey Smirnov
2019-03-21 13:12 ` Tomi Valkeinen
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