From: Chen-Yu Tsai <wenst@chromium.org> To: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Rob Herring <robh+dt@kernel.org>, Frank Rowand <frowand.list@gmail.com>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>, Matthias Brugger <matthias.bgg@gmail.com>, AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>, Wolfram Sang <wsa@kernel.org>, Benson Leung <bleung@chromium.org>, Tzung-Bi Shih <tzungbi@kernel.org>, chrome-platform@lists.linux.dev, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, Douglas Anderson <dianders@chromium.org>, Johan Hovold <johan@kernel.org>, Hsin-Yi Wang <hsinyi@chromium.org>, Dmitry Torokhov <dmitry.torokhov@gmail.com>, Jiri Kosina <jikos@kernel.org>, linus.walleij@linaro.org, broonie@kernel.org, gregkh@linuxfoundation.org, hdegoede@redhat.com, james.clark@arm.com, james@equiv.tech, keescook@chromium.org, rafael@kernel.org, tglx@linutronix.de, Jeff LaBundy <jeff@labundy.com>, linux-input@vger.kernel.org, linux-i2c@vger.kernel.org Subject: Re: [RFC PATCH v3 2/5] i2c: of: Introduce component probe function Date: Wed, 29 Nov 2023 16:20:08 +0800 [thread overview] Message-ID: <CAGXv+5EBBtbpDA8scVBFysYrk6s8JUd_-JcqbX3oubO60Uc_ZA@mail.gmail.com> (raw) In-Reply-To: <ZWYTzGGToEmSu-Yh@smile.fi.intel.com> On Wed, Nov 29, 2023 at 12:22 AM Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > On Tue, Nov 28, 2023 at 04:42:31PM +0800, Chen-Yu Tsai wrote: > > Some devices are designed and manufactured with some components having > > multiple drop-in replacement options. These components are often > > connected to the mainboard via ribbon cables, having the same signals > > and pin assignments across all options. These may include the display > > panel and touchscreen on laptops and tablets, and the trackpad on > > laptops. Sometimes which component option is used in a particular device > > can be detected by some firmware provided identifier, other times that > > information is not available, and the kernel has to try to probe each > > device. > > > > This change attempts to make the "probe each device" case cleaner. The > > current approach is to have all options added and enabled in the device > > tree. The kernel would then bind each device and run each driver's probe > > function. This works, but has been broken before due to the introduction > > of asynchronous probing, causing multiple instances requesting "shared" > > resources, such as pinmuxes, GPIO pins, interrupt lines, at the same > > time, with only one instance succeeding. Work arounds for these include > > moving the pinmux to the parent I2C controller, using GPIO hogs or > > pinmux settings to keep the GPIO pins in some fixed configuration, and > > requesting the interrupt line very late. Such configurations can be seen > > on the MT8183 Krane Chromebook tablets, and the Qualcomm sc8280xp-based > > Lenovo Thinkpad 13S. > > > > Instead of this delicate dance between drivers and device tree quirks, > > this change introduces a simple I2C component probe. function For a > > given class of devices on the same I2C bus, it will go through all of > > them, doing a simple I2C read transfer and see which one of them responds. > > It will then enable the device that responds. > > > > This requires some minor modifications in the existing device tree. The > > status for all the device nodes for the component options must be set > > to "failed-needs-probe". This makes it clear that some mechanism is > > needed to enable one of them, and also prevents the prober and device > > drivers running at the same time. > > ... > > > +/** > > + * i2c_of_probe_component() - probe for devices of "type" on the same i2c bus > > + * @dev: &struct device of the caller, only used for dev_* printk messages > > + * @type: a string to match the device node name prefix to probe for > > + * > > + * Probe for possible I2C components of the same "type" on the same I2C bus > > + * that have their status marked as "fail". > > Definitely you haven't run kernel-doc validation. Right. Will add missing parts. > > + */ > > ... > > > + return dev_err_probe(dev, -ENODEV, "Could not find %s device node\n", type); > > I haven't noticed clear statement in the description that this API is only for > the ->probe() stages. Will add that to the Context part of the kernel-doc. > ... > > > + if (i2c_smbus_xfer(i2c, addr, 0, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &data) < 0) > > + continue; > > This will require the device to be powered on. Are you sure it will be always > the case? This is left as TODO. The devices I have tie the component power supplies to an always on power rail. I guess I could get a trace of the function calls to see if things are running as they should. Not sure if that is enough? ChenYu
WARNING: multiple messages have this Message-ID (diff)
From: Chen-Yu Tsai <wenst@chromium.org> To: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Rob Herring <robh+dt@kernel.org>, Frank Rowand <frowand.list@gmail.com>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>, Matthias Brugger <matthias.bgg@gmail.com>, AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>, Wolfram Sang <wsa@kernel.org>, Benson Leung <bleung@chromium.org>, Tzung-Bi Shih <tzungbi@kernel.org>, chrome-platform@lists.linux.dev, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, Douglas Anderson <dianders@chromium.org>, Johan Hovold <johan@kernel.org>, Hsin-Yi Wang <hsinyi@chromium.org>, Dmitry Torokhov <dmitry.torokhov@gmail.com>, Jiri Kosina <jikos@kernel.org>, linus.walleij@linaro.org, broonie@kernel.org, gregkh@linuxfoundation.org, hdegoede@redhat.com, james.clark@arm.com, james@equiv.tech, keescook@chromium.org, rafael@kernel.org, tglx@linutronix.de, Jeff LaBundy <jeff@labundy.com>, linux-input@vger.kernel.org, linux-i2c@vger.kernel.org Subject: Re: [RFC PATCH v3 2/5] i2c: of: Introduce component probe function Date: Wed, 29 Nov 2023 16:20:08 +0800 [thread overview] Message-ID: <CAGXv+5EBBtbpDA8scVBFysYrk6s8JUd_-JcqbX3oubO60Uc_ZA@mail.gmail.com> (raw) In-Reply-To: <ZWYTzGGToEmSu-Yh@smile.fi.intel.com> On Wed, Nov 29, 2023 at 12:22 AM Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > On Tue, Nov 28, 2023 at 04:42:31PM +0800, Chen-Yu Tsai wrote: > > Some devices are designed and manufactured with some components having > > multiple drop-in replacement options. These components are often > > connected to the mainboard via ribbon cables, having the same signals > > and pin assignments across all options. These may include the display > > panel and touchscreen on laptops and tablets, and the trackpad on > > laptops. Sometimes which component option is used in a particular device > > can be detected by some firmware provided identifier, other times that > > information is not available, and the kernel has to try to probe each > > device. > > > > This change attempts to make the "probe each device" case cleaner. The > > current approach is to have all options added and enabled in the device > > tree. The kernel would then bind each device and run each driver's probe > > function. This works, but has been broken before due to the introduction > > of asynchronous probing, causing multiple instances requesting "shared" > > resources, such as pinmuxes, GPIO pins, interrupt lines, at the same > > time, with only one instance succeeding. Work arounds for these include > > moving the pinmux to the parent I2C controller, using GPIO hogs or > > pinmux settings to keep the GPIO pins in some fixed configuration, and > > requesting the interrupt line very late. Such configurations can be seen > > on the MT8183 Krane Chromebook tablets, and the Qualcomm sc8280xp-based > > Lenovo Thinkpad 13S. > > > > Instead of this delicate dance between drivers and device tree quirks, > > this change introduces a simple I2C component probe. function For a > > given class of devices on the same I2C bus, it will go through all of > > them, doing a simple I2C read transfer and see which one of them responds. > > It will then enable the device that responds. > > > > This requires some minor modifications in the existing device tree. The > > status for all the device nodes for the component options must be set > > to "failed-needs-probe". This makes it clear that some mechanism is > > needed to enable one of them, and also prevents the prober and device > > drivers running at the same time. > > ... > > > +/** > > + * i2c_of_probe_component() - probe for devices of "type" on the same i2c bus > > + * @dev: &struct device of the caller, only used for dev_* printk messages > > + * @type: a string to match the device node name prefix to probe for > > + * > > + * Probe for possible I2C components of the same "type" on the same I2C bus > > + * that have their status marked as "fail". > > Definitely you haven't run kernel-doc validation. Right. Will add missing parts. > > + */ > > ... > > > + return dev_err_probe(dev, -ENODEV, "Could not find %s device node\n", type); > > I haven't noticed clear statement in the description that this API is only for > the ->probe() stages. Will add that to the Context part of the kernel-doc. > ... > > > + if (i2c_smbus_xfer(i2c, addr, 0, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &data) < 0) > > + continue; > > This will require the device to be powered on. Are you sure it will be always > the case? This is left as TODO. The devices I have tie the component power supplies to an always on power rail. I guess I could get a trace of the function calls to see if things are running as they should. Not sure if that is enough? ChenYu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2023-11-29 8:20 UTC|newest] Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-11-28 8:42 [RFC PATCH v3 0/5] platform/chrome: Introduce DT hardware prober Chen-Yu Tsai 2023-11-28 8:42 ` Chen-Yu Tsai 2023-11-28 8:42 ` [RFC PATCH v3 1/5] of: dynamic: Add of_changeset_update_prop_string Chen-Yu Tsai 2023-11-28 8:42 ` Chen-Yu Tsai 2023-12-02 0:56 ` Doug Anderson 2023-12-02 0:56 ` Doug Anderson 2023-12-04 6:28 ` Chen-Yu Tsai 2023-12-04 6:28 ` Chen-Yu Tsai 2023-11-28 8:42 ` [RFC PATCH v3 2/5] i2c: of: Introduce component probe function Chen-Yu Tsai 2023-11-28 8:42 ` Chen-Yu Tsai 2023-11-28 16:22 ` Andy Shevchenko 2023-11-28 16:22 ` Andy Shevchenko 2023-11-29 8:20 ` Chen-Yu Tsai [this message] 2023-11-29 8:20 ` Chen-Yu Tsai 2023-12-02 0:57 ` Doug Anderson 2023-12-02 0:57 ` Doug Anderson 2023-12-04 9:52 ` Chen-Yu Tsai 2023-12-04 9:52 ` Chen-Yu Tsai 2023-12-04 16:03 ` Doug Anderson 2023-12-04 16:03 ` Doug Anderson 2023-12-08 15:10 ` Rob Herring 2023-12-08 15:10 ` Rob Herring 2023-11-28 8:42 ` [RFC PATCH v3 3/5] platform/chrome: Introduce device tree hardware prober Chen-Yu Tsai 2023-11-28 8:42 ` Chen-Yu Tsai 2023-11-28 16:25 ` Andy Shevchenko 2023-11-28 16:25 ` Andy Shevchenko 2023-11-29 8:23 ` Chen-Yu Tsai 2023-11-29 8:23 ` Chen-Yu Tsai 2023-12-02 0:58 ` Doug Anderson 2023-12-02 0:58 ` Doug Anderson 2023-12-04 7:24 ` Chen-Yu Tsai 2023-12-04 7:24 ` Chen-Yu Tsai 2023-12-04 7:53 ` Chen-Yu Tsai 2023-12-04 7:53 ` Chen-Yu Tsai 2023-12-03 6:31 ` kernel test robot 2023-12-06 21:41 ` kernel test robot 2023-11-28 8:42 ` [RFC PATCH v3 4/5] arm64: dts: mediatek: mt8173-elm-hana: Mark touchscreens and trackpads as fail Chen-Yu Tsai 2023-11-28 8:42 ` Chen-Yu Tsai 2023-12-02 0:58 ` Doug Anderson 2023-12-02 0:58 ` Doug Anderson 2023-12-04 6:59 ` Chen-Yu Tsai 2023-12-04 6:59 ` Chen-Yu Tsai 2023-12-04 16:50 ` Doug Anderson 2023-12-04 16:50 ` Doug Anderson 2023-12-05 10:22 ` AngeloGioacchino Del Regno 2023-12-05 10:22 ` AngeloGioacchino Del Regno 2023-12-06 2:55 ` Chen-Yu Tsai 2023-12-06 2:55 ` Chen-Yu Tsai 2023-12-06 10:02 ` AngeloGioacchino Del Regno 2023-12-06 10:02 ` AngeloGioacchino Del Regno 2023-12-06 17:00 ` Doug Anderson 2023-12-06 17:00 ` Doug Anderson 2023-11-28 8:42 ` [RFC PATCH v3 5/5] arm64: dts: mediatek: mt8173-elm-hana: Add G2touch G7500 touchscreen Chen-Yu Tsai 2023-11-28 8:42 ` Chen-Yu Tsai
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