| Message ID | 20240904090016.2841572-12-wenst@chromium.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | platform/chrome: Introduce DT hardware prober | expand |
On Wed, Sep 04, 2024 at 05:00:13PM +0800, Chen-Yu Tsai wrote: > diff --git a/drivers/platform/chrome/chromeos_of_hw_prober.c b/drivers/platform/chrome/chromeos_of_hw_prober.c [...] > +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) > +{ > + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) { > + int ret; > + > + if (!of_machine_is_compatible(hw_prober_platforms[i].compatible)) > + continue; > + > + ret = hw_prober_platforms[i].prober(&pdev->dev, hw_prober_platforms[i].data); > + /* Ignore unrecoverable errors and keep going through other probers */ > + if (ret == -EPROBE_DEFER) > + return ret; Is it harmless if some of the components get probed multiple times? E.g.: comp1 probed -> comp2 probed -> comp3 returned -EPROBE_DEFER -> some time later, chromeos_of_hw_prober_probe() gets called again.
On Wed, Sep 4, 2024 at 6:08 PM Tzung-Bi Shih <tzungbi@kernel.org> wrote: > > On Wed, Sep 04, 2024 at 05:00:13PM +0800, Chen-Yu Tsai wrote: > > diff --git a/drivers/platform/chrome/chromeos_of_hw_prober.c b/drivers/platform/chrome/chromeos_of_hw_prober.c > [...] > > +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) > > +{ > > + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) { > > + int ret; > > + > > + if (!of_machine_is_compatible(hw_prober_platforms[i].compatible)) > > + continue; > > + > > + ret = hw_prober_platforms[i].prober(&pdev->dev, hw_prober_platforms[i].data); > > + /* Ignore unrecoverable errors and keep going through other probers */ > > + if (ret == -EPROBE_DEFER) > > + return ret; > > Is it harmless if some of the components get probed multiple times? E.g.: > comp1 probed -> comp2 probed -> comp3 returned -EPROBE_DEFER -> some time > later, chromeos_of_hw_prober_probe() gets called again. Yes it is harmless. Components already enabled will not get disabled in the error path. And the prober that enabled that component will see that a component was enabled, and skip doing the whole process again. So something like: comp1 probed -> comp2 probed -> comp3 -EPROBE_DEFER -> comp1 skip -> comp2 skip -> comp3 probed ChenYu
On Thu, Sep 05, 2024 at 11:52:32AM +0800, Chen-Yu Tsai wrote: > On Wed, Sep 4, 2024 at 6:08 PM Tzung-Bi Shih <tzungbi@kernel.org> wrote: > > > > On Wed, Sep 04, 2024 at 05:00:13PM +0800, Chen-Yu Tsai wrote: > > > diff --git a/drivers/platform/chrome/chromeos_of_hw_prober.c b/drivers/platform/chrome/chromeos_of_hw_prober.c > > [...] > > > +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) > > > +{ > > > + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) { > > > + int ret; > > > + > > > + if (!of_machine_is_compatible(hw_prober_platforms[i].compatible)) > > > + continue; > > > + > > > + ret = hw_prober_platforms[i].prober(&pdev->dev, hw_prober_platforms[i].data); > > > + /* Ignore unrecoverable errors and keep going through other probers */ > > > + if (ret == -EPROBE_DEFER) > > > + return ret; > > > > Is it harmless if some of the components get probed multiple times? E.g.: > > comp1 probed -> comp2 probed -> comp3 returned -EPROBE_DEFER -> some time > > later, chromeos_of_hw_prober_probe() gets called again. > > Yes it is harmless. Components already enabled will not get disabled > in the error path. And the prober that enabled that component will see > that a component was enabled, and skip doing the whole process again. > > So something like: > > comp1 probed -> comp2 probed -> comp3 -EPROBE_DEFER -> > comp1 skip -> comp2 skip -> comp3 probed I assume this patch will be applied through the i2c tree: Acked-by: Tzung-Bi Shih <tzungbi@kernel.org>
diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig index 7dbeb786352a..b7dbaf77b6db 100644 --- a/drivers/platform/chrome/Kconfig +++ b/drivers/platform/chrome/Kconfig @@ -61,6 +61,17 @@ config CHROMEOS_TBMC To compile this driver as a module, choose M here: the module will be called chromeos_tbmc. +config CHROMEOS_OF_HW_PROBER + tristate "ChromeOS Device Tree Hardware Prober" + depends on OF + depends on I2C + select OF_DYNAMIC + default OF + help + This option enables the device tree hardware prober for ChromeOS + devices. The driver will probe the correct component variant in + devices that have multiple drop-in options for one component. + config CROS_EC tristate "ChromeOS Embedded Controller" select CROS_EC_PROTO diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile index 2dcc6ccc2302..21a9d5047053 100644 --- a/drivers/platform/chrome/Makefile +++ b/drivers/platform/chrome/Makefile @@ -8,6 +8,7 @@ obj-$(CONFIG_CHROMEOS_ACPI) += chromeos_acpi.o obj-$(CONFIG_CHROMEOS_LAPTOP) += chromeos_laptop.o obj-$(CONFIG_CHROMEOS_PRIVACY_SCREEN) += chromeos_privacy_screen.o obj-$(CONFIG_CHROMEOS_PSTORE) += chromeos_pstore.o +obj-$(CONFIG_CHROMEOS_OF_HW_PROBER) += chromeos_of_hw_prober.o obj-$(CONFIG_CHROMEOS_TBMC) += chromeos_tbmc.o obj-$(CONFIG_CROS_EC) += cros_ec.o obj-$(CONFIG_CROS_EC_I2C) += cros_ec_i2c.o diff --git a/drivers/platform/chrome/chromeos_of_hw_prober.c b/drivers/platform/chrome/chromeos_of_hw_prober.c new file mode 100644 index 000000000000..90fc1de16788 --- /dev/null +++ b/drivers/platform/chrome/chromeos_of_hw_prober.c @@ -0,0 +1,104 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * ChromeOS Device Tree Hardware Prober + * + * Copyright (c) 2024 Google LLC + */ + +#include <linux/array_size.h> +#include <linux/errno.h> +#include <linux/i2c.h> +#include <linux/module.h> +#include <linux/platform_device.h> + +#define DRV_NAME "chromeos_of_hw_prober" + +/** + * struct hw_prober_entry - Holds an entry for the hardware prober + * + * @compatible: compatible string to match against the machine + * @prober: prober function to call when machine matches + * @data: extra data for the prober function + */ +struct hw_prober_entry { + const char *compatible; + int (*prober)(struct device *dev, const void *data); + const void *data; +}; + +static int chromeos_i2c_component_prober(struct device *dev, const void *data) +{ + const char *type = data; + + return i2c_of_probe_component(dev, type, NULL); +} + +static const struct hw_prober_entry hw_prober_platforms[] = { + { .compatible = "google,hana", .prober = chromeos_i2c_component_prober, .data = "touchscreen" }, + { .compatible = "google,hana", .prober = chromeos_i2c_component_prober, .data = "trackpad" }, +}; + +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) +{ + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) { + int ret; + + if (!of_machine_is_compatible(hw_prober_platforms[i].compatible)) + continue; + + ret = hw_prober_platforms[i].prober(&pdev->dev, hw_prober_platforms[i].data); + /* Ignore unrecoverable errors and keep going through other probers */ + if (ret == -EPROBE_DEFER) + return ret; + } + + return 0; +} + +static struct platform_driver chromeos_of_hw_prober_driver = { + .probe = chromeos_of_hw_prober_probe, + .driver = { + .name = DRV_NAME, + }, +}; + +static struct platform_device *chromeos_of_hw_prober_pdev; + +static int chromeos_of_hw_prober_driver_init(void) +{ + size_t i; + int ret; + + for (i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) + if (of_machine_is_compatible(hw_prober_platforms[i].compatible)) + break; + if (i == ARRAY_SIZE(hw_prober_platforms)) + return -ENODEV; + + ret = platform_driver_register(&chromeos_of_hw_prober_driver); + if (ret) + return ret; + + chromeos_of_hw_prober_pdev = + platform_device_register_simple(DRV_NAME, PLATFORM_DEVID_NONE, NULL, 0); + if (IS_ERR(chromeos_of_hw_prober_pdev)) + goto err; + + return 0; + +err: + platform_driver_unregister(&chromeos_of_hw_prober_driver); + + return PTR_ERR(chromeos_of_hw_prober_pdev); +} +module_init(chromeos_of_hw_prober_driver_init); + +static void chromeos_of_hw_prober_driver_exit(void) +{ + platform_device_unregister(chromeos_of_hw_prober_pdev); + platform_driver_unregister(&chromeos_of_hw_prober_driver); +} +module_exit(chromeos_of_hw_prober_driver_exit); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("ChromeOS device tree hardware prober");
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 prober. For any 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. Signed-off-by: Chen-Yu Tsai <wenst@chromium.org> --- Changes since v5: - Adapt to new i2c_of_probe_component() parameters Changes since v4: - Fix Kconfig dependency - Update copyright year - Drop "linux/of.h" header - Include "linux/errno.h" - Move |int ret| declaration to top of block - Return -ENODEV on no match instead of 0 - Unregister platform driver and device unconditionally after previous change Changes since v3: - Include linux/init.h - Rewrite for loop in driver probe function as suggested by Andy - Make prober driver buildable as module - Ignore prober errors other than probe deferral Changes since v2: - Addressed Rob's comments - Move remaining driver code to drivers/platform/chrome/ - Depend on rather than select CONFIG_I2C - Copy machine check to driver init function - Addressed Andy's comments - Explicitly mention "device tree" or OF in driver name, description and Kconfig symbol - Drop filename from inside the file - Switch to passing "struct device *" to shorten lines - Move "ret = 0" to just before for_each_child_of_node(i2c_node, node) - Make loop variable size_t (instead of unsigned int as Andy asked) - Use PLATFORM_DEVID_NONE instead of raw -1 - Use standard goto error path pattern in hw_prober_driver_init() - Changes since v1: - New patch --- drivers/platform/chrome/Kconfig | 11 ++ drivers/platform/chrome/Makefile | 1 + .../platform/chrome/chromeos_of_hw_prober.c | 104 ++++++++++++++++++ 3 files changed, 116 insertions(+) create mode 100644 drivers/platform/chrome/chromeos_of_hw_prober.c