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Wed, 10 Nov 2021 12:25:14 -0800 (PST) MIME-Version: 1.0 References: <20210929000735.585237-1-saravanak@google.com> <20210929000735.585237-2-saravanak@google.com> In-Reply-To: From: Saravana Kannan Date: Wed, 10 Nov 2021 12:24:38 -0800 Message-ID: Subject: Re: [PATCH v4 1/2] drivers: bus: simple-pm-bus: Add support for probing simple bus only devices To: Abel Vesa Cc: Russell King , Neil Armstrong , Geert Uytterhoeven , Magnus Damm , Tony Lindgren , Catalin Marinas , Will Deacon , Damien Le Moal , Greg Kroah-Hartman , Ulf Hansson , Rob Herring , kernel-team@android.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-oxnas@groups.io, linux-renesas-soc@vger.kernel.org, linux-omap@vger.kernel.org, linux-riscv@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211110_122518_440633_5BFAD84D X-CRM114-Status: GOOD ( 47.00 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Nov 10, 2021 at 4:16 AM Abel Vesa wrote: > > On 21-09-28 17:07:33, Saravana Kannan wrote: > > fw_devlink could end up creating device links for bus only devices. > > However, bus only devices don't get probed and can block probe() or > > sync_state() [1] call backs of other devices. To avoid this, probe these > > devices using the simple-pm-bus driver. > > > > However, there are instances of devices that are not simple buses (they get > > probed by their specific drivers) that also list the "simple-bus" (or other > > bus only compatible strings) in their compatible property to automatically > > populate their child devices. We still want these devices to get probed by > > their specific drivers. So, we make sure this driver only probes devices > > that are only buses. > > > > [1] - https://lore.kernel.org/lkml/CAPDyKFo9Bxremkb1dDrr4OcXSpE0keVze94Cm=zrkOVxHHxBmQ@mail.gmail.com/ > > Fixes: c442a0d18744 ("driver core: Set fw_devlink to "permissive" behavior by default") > > Signed-off-by: Saravana Kannan > > Tested-by: Saravana Kannan > > Tested-by: Ulf Hansson > > --- > > drivers/bus/simple-pm-bus.c | 42 ++++++++++++++++++++++++++++++++++--- > > 1 file changed, 39 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c > > index 01a3d0cd08ed..6b8d6257ed8a 100644 > > --- a/drivers/bus/simple-pm-bus.c > > +++ b/drivers/bus/simple-pm-bus.c > > @@ -13,11 +13,36 @@ > > #include > > #include > > > > - > > static int simple_pm_bus_probe(struct platform_device *pdev) > > { > > - const struct of_dev_auxdata *lookup = dev_get_platdata(&pdev->dev); > > - struct device_node *np = pdev->dev.of_node; > > + const struct device *dev = &pdev->dev; > > + const struct of_dev_auxdata *lookup = dev_get_platdata(dev); > > + struct device_node *np = dev->of_node; > > + const struct of_device_id *match; > > + > > + /* > > + * Allow user to use driver_override to bind this driver to a > > + * transparent bus device which has a different compatible string > > + * that's not listed in simple_pm_bus_of_match. We don't want to do any > > + * of the simple-pm-bus tasks for these devices, so return early. > > + */ > > + if (pdev->driver_override) > > + return 0; > > + > > + match = of_match_device(dev->driver->of_match_table, dev); > > + /* > > + * These are transparent bus devices (not simple-pm-bus matches) that > > + * have their child nodes populated automatically. So, don't need to > > + * do anything more. We only match with the device if this driver is > > + * the most specific match because we don't want to incorrectly bind to > > + * a device that has a more specific driver. > > + */ > > + if (match && match->data) { > > + if (of_property_match_string(np, "compatible", match->compatible) == 0) > > + return 0; > > + else > > + return -ENODEV; > > + } > > This change is breaking the expected behavior for the already existent > simple-bus nodes. All the simple-bus compatibles should be replaced now > to simple-pm-bus. In my case, on some i.MX8 platforms, without the > devlink, the devices suspend sequence changes (and even breaks). > > To avoid breaking the already existent simple-bus nodes, maybe the logic > should've been reversed: keep the simple-bus as is and add another > compatible, IDK, something like simple-trasnparent-bus, or something. The intent of this change IS to affect existing simple-bus nodes (but not in the way it's affecting you). But if it's breaking stuff, we obviously need to fix it. I have a hunch on what's going on in your case, but can you point me to the specific simple-bus node that's getting affected? I'm expecting it to be a simple-bus node that gets added AFTER this driver is registered at device_initcall (module_init gets converted to device_initcall). Also, can you try this hack patch to see if it helps your case? https://lore.kernel.org/lkml/CAGETcx9U130Oq-umrvXME4JhEpO0Wadoki3kNxx=0-YvTR6PtQ@mail.gmail.com/ I have some thoughts on how I could fix this, but I need to think about a few cases. -Saravana > > > > > dev_dbg(&pdev->dev, "%s\n", __func__); > > > > @@ -31,14 +56,25 @@ static int simple_pm_bus_probe(struct platform_device *pdev) > > > > static int simple_pm_bus_remove(struct platform_device *pdev) > > { > > + const void *data = of_device_get_match_data(&pdev->dev); > > + > > + if (pdev->driver_override || data) > > + return 0; > > + > > dev_dbg(&pdev->dev, "%s\n", __func__); > > > > pm_runtime_disable(&pdev->dev); > > return 0; > > } > > > > +#define ONLY_BUS ((void *) 1) /* Match if the device is only a bus. */ > > + > > static const struct of_device_id simple_pm_bus_of_match[] = { > > { .compatible = "simple-pm-bus", }, > > + { .compatible = "simple-bus", .data = ONLY_BUS }, > > + { .compatible = "simple-mfd", .data = ONLY_BUS }, > > + { .compatible = "isa", .data = ONLY_BUS }, > > + { .compatible = "arm,amba-bus", .data = ONLY_BUS }, > > { /* sentinel */ } > > }; > > MODULE_DEVICE_TABLE(of, simple_pm_bus_of_match); > > -- > > 2.33.0.685.g46640cef36-goog > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel