From: Stephen Boyd <swboyd@chromium.org>
To: Douglas Anderson <dianders@chromium.org>,
Laurent.pinchart@ideasonboard.com, a.hajda@samsung.com,
airlied@linux.ie, bgolaszewski@baylibre.com, daniel@ffwll.ch,
linus.walleij@linaro.org, narmstrong@baylibre.com,
robh+dt@kernel.org, spanda@codeaurora.org
Cc: jonas@kwiboo.se, jeffrey.l.hugo@gmail.com,
linux-gpio@vger.kernel.org, bjorn.andersson@linaro.org,
jernej.skrabec@siol.net, devicetree@vger.kernel.org,
dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org,
robdclark@chromium.org, Douglas Anderson <dianders@chromium.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/6] drm/bridge: ti-sn65dsi86: Export bridge GPIOs to Linux
Date: Mon, 11 May 2020 09:24:09 -0700 [thread overview]
Message-ID: <158921424955.26370.14824525920971881719@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <20200507143354.v5.1.Ia50267a5549392af8b37e67092ca653a59c95886@changeid>
Quoting Douglas Anderson (2020-05-07 14:34:55)
> The ti-sn65dsi86 MIPI DSI to eDP bridge chip has 4 pins on it that can
> be used as GPIOs in a system. Each pin can be configured as input,
> output, or a special function for the bridge chip. These are:
> - GPIO1: SUSPEND Input
> - GPIO2: DSIA VSYNC
> - GPIO3: DSIA HSYNC or VSYNC
> - GPIO4: PWM
>
> Let's expose these pins as GPIOs. A few notes:
> - Access to ti-sn65dsi86 is via i2c so we set "can_sleep".
> - These pins can't be configured for IRQ.
> - There are no programmable pulls or other fancy features.
> - Keeping the bridge chip powered might be expensive. The driver is
> setup such that if all used GPIOs are only inputs we'll power the
> bridge chip on just long enough to read the GPIO and then power it
> off again. Setting a GPIO as output will keep the bridge powered.
> - If someone releases a GPIO we'll implicitly switch it to an input so
> we no longer need to keep the bridge powered for it.
>
> Because of all of the above limitations we just need to implement a
> bare-bones GPIO driver. The device tree bindings already account for
> this device being a GPIO controller so we only need the driver changes
> for it.
>
> NOTE: Despite the fact that these pins are nominally muxable I don't
> believe it makes sense to expose them through the pinctrl interface as
> well as the GPIO interface. The special functions are things that the
> bridge chip driver itself would care about and it can just configure
> the pins as needed.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> ---
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
next prev parent reply other threads:[~2020-05-11 16:24 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-07 21:34 [PATCH v5 0/6] drm: Prepare to use a GPIO on ti-sn65dsi86 for Hot Plug Detect Douglas Anderson
2020-05-07 21:34 ` [PATCH v5 1/6] drm/bridge: ti-sn65dsi86: Export bridge GPIOs to Linux Douglas Anderson
2020-05-11 16:24 ` Stephen Boyd [this message]
2020-05-12 1:36 ` Bjorn Andersson
2020-05-12 12:28 ` Linus Walleij
2020-05-07 21:34 ` [PATCH v5 2/6] dt-bindings: display: Add hpd-gpios to panel-common bindings Douglas Anderson
2020-05-07 21:34 ` [PATCH v5 3/6] drm/panel-simple: Support hpd-gpios for delaying prepare() Douglas Anderson
2020-05-07 21:34 ` [PATCH v5 4/6] dt-bindings: drm/bridge: ti-sn65dsi86: Convert to yaml Douglas Anderson
2020-05-11 16:25 ` Stephen Boyd
2020-05-07 21:34 ` [PATCH v5 5/6] dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd Douglas Anderson
2020-05-07 21:35 ` [PATCH v5 6/6] arm64: dts: sdm845: Add "no-hpd" to sn65dsi86 on cheza Douglas Anderson
2020-05-12 1:21 ` Bjorn Andersson
2020-05-09 20:15 ` [PATCH v5 0/6] drm: Prepare to use a GPIO on ti-sn65dsi86 for Hot Plug Detect Sam Ravnborg
2020-05-09 22:48 ` Doug Anderson
2020-05-18 14:50 ` Doug Anderson
2020-05-18 17:59 ` Sam Ravnborg
2020-05-18 18:05 ` Doug Anderson
2020-05-18 18:28 ` Sam Ravnborg
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