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Mon, 29 Jun 2026 18:47:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B611A1F000E9; Mon, 29 Jun 2026 18:47:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782758830; bh=pSgBVAPBB9xsQxek5fY18KbTNXVt834G10JH70EWozU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=NWtctKaJD+09V8wyK/qnFMLkpaS71wFZCmariqaedWVtN6lBpRx5GFIR36vzNb6HP ZXqJpITx90gbGUpZiI0slDwKD6lDTj9EOTatt+KMP9thMuwO8SpHKnReAce/hEN3Lz ni3iPsidb/vRw2cjnm0uHX+fFgtynD6XRfxxhtgmEnbKqSGhGNMj8DPTQEY3CY4Xv2 HbWOCFJPRZguXS22Qx/rfXMKgWGJyRg2qTukj07ZNmhasRm5zUPYspyo9zTZ/2UKbW FjCxB5aWURUJFJTITAjFa2amfJd0I5TzYmRDS7bNvyXeACqoHZceqJZ5RHwasvQ93V U25qoPHBtd4eg== Message-ID: <20c972b7-02f1-4e92-8bb5-5696ae64696d@kernel.org> Date: Mon, 29 Jun 2026 20:47:04 +0200 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 1/3] powerpc/perf: Register PMU from device tree and expose events To: Shivani Nittor , maddy@linux.ibm.com, linuxppc-dev@lists.ozlabs.org Cc: linux-kernel@vger.kernel.org, atrajeev@linux.ibm.com, tshah@linux.ibm.com References: <20260629061101.43119-1-shivani@linux.ibm.com> <20260629061101.43119-2-shivani@linux.ibm.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 29/06/2026 08:10, Shivani Nittor wrote: > Introduce a DTS-based PMU driver that discovers PMU information > from the device tree and registers a PowerPC PMU instance at > runtime. > > The driver parses basic PMU properties such as the number of > counters and MMCR register definitions, creates sysfs event > entries from the device tree event descriptions, and registers > the PMU with the perf subsystem. > > To support dynamic PMU registration, add PMU unregistration > support and create a platform device for PMU nodes described > in the device tree. > > This forms the foundation for moving PMU descriptions out of > architecture-specific kernel code and into device tree data. > > The driver implements the following functionality: > > Device Tree Parsing: > - Reads PMU properties including counter count (nr_pmc), PMU name, > version, and platform information > - Parses MMCR (Monitor Mode Control Register) definitions from the > sprs/mmcr node hierarchy, storing the MMCR register SPRNs > - Extracts event definitions from the events node, supporting both > 32-bit and 64-bit event codes > > Dynamic Event Registration: > - Creates sysfs event entries dynamically from device tree event > descriptions > - Generates event attributes with format "event=0x" for each > discovered event > - Exposes events under /sys/devices//events/ > > PMU Registration: > - Registers a power_pmu instance with the perf subsystem using the > device tree-provided PMU name > - Adds PMU unregistration support to enable proper cleanup > - Creates platform device for "ibm,power-pmu" compatible nodes > > Sysfs Interface: > - Provides format attributes (event, pmcsel) under > /sys/devices//format/ > - Exposes device tree debug information (nr_pmc) under > /sys/devices//dt/ Where did you document the ABI? ... > +static struct power_pmu dts_pmu = { > + .name = "cpu_dts", > + .n_counter = MAX_PMU_COUNTERS, > + .attr_groups = pmu_dts_attr_groups, > +}; > + > +/* Device Tree match */ That's obvious. Can of_device_id be something else than DT match? > +static const struct of_device_id pmu_dts_of_match[] = { > + { .compatible = "ibm,power-pmu" }, Where is ABI documented? > + { } > +}; > +MODULE_DEVICE_TABLE(of, pmu_dts_of_match); > + > +/* Probe function */ > +static int pmu_dts_probe(struct platform_device *pdev) > +{ > + struct device_node *np = pdev->dev.of_node, *child, *events_np; > + struct device_node *sprs_np, *mmcr_np, *mmcr_child; > + struct pmu_dts_event *evt; > + u64 code; > + u32 code32, sprn; > + u32 code64[2]; > + u32 code128[4]; > + int cells; > + const char *str; > + > + pr_info("PMU DTS probe node = %s\n", np->full_name); This does not look like useful printk message. Drivers should be silent on success: https://elixir.bootlin.com/linux/v6.15-rc7/source/Documentation/process/coding-style.rst#L913 https://elixir.bootlin.com/linux/v6.15-rc7/source/Documentation/process/debugging/driver_development_debugging_guide.rst#L79 > + > + if (!of_property_present(np, "nr_pmc")) { > + > + for_each_child_of_node(np, child) { > + pr_info("child node = %s\n", child->full_name); Why are you sending debugging code? > + > + if (of_property_present(child, "nr_pmc")) { > + np = child; > + break; > + } > + } > + } > + > + if (of_property_read_u32(np, "nr_pmc", &pmu_dts_nr_pmc)) { > + pr_err("pmu_dts: nr_pmc not found in %s\n", np->full_name); Why isn't this using dev interface? > + return -EINVAL; > + } > + > + if (!of_property_read_string(np, "pmu-name", &str)) > + pr_info("PMU Name: %s\n", str); > + > + if (!of_property_read_string(np, "pmu-version", &str)) > + pr_info("PMU Version: %s\n", str); > + > + if (!of_property_read_string(np, "platform", &str)) No, you cannot just add bunch of undocumented ABI and call it a day. > + pr_info("Platform: %s\n", str); > + > + sprs_np = of_get_child_by_name(np, "sprs"); > + if (!sprs_np) { > + pr_err("pmu_dts: no sprs node\n"); > + return -EINVAL; > + } > + > + mmcr_np = of_get_child_by_name(sprs_np, "mmcr"); > + if (!mmcr_np) { > + pr_err("pmu_dts: no mmcr node\n"); > + return -EINVAL; > + } > + > + mmcr_count = 0; > + for_each_child_of_node(mmcr_np, mmcr_child) { > + > + if (of_property_read_u32(mmcr_child, "sprn", &sprn)) > + continue; > + > + mmcr_regs_sprs[mmcr_count++] = sprn; > + pr_info("pmu_dts: MMCR[%d] = %u (%s)\n", mmcr_count - 1, > + sprn, mmcr_child->name); > + > + if (mmcr_count >= MAX_MMCR) > + break; Where is cleanup? > + } > + > + if (!mmcr_count) { > + pr_err("pmu_dts: no MMCR SPRs found\n"); > + return -EINVAL; > + } > + > + /* Parse events */ > + events_np = of_get_child_by_name(np, "events"); > + if (!events_np) { > + pr_err("pmu_dts: no events node found\n"); > + return -EINVAL; > + } > + > + dts_event_count = 0; > + for_each_child_of_node(events_np, child) { > + if (!of_device_is_available(child)) Why are you open-coding available variant of loop? > + continue; > + > + cells = of_property_count_u32_elems(child, "event_code"); > + if (cells == 1) { > + if (of_property_read_u32(child, "event_code", &code32)) > + continue; > + > + code = code32; > + > + } else if (cells == 2) { > + if (of_property_read_u32_array(child, "event_code", code64, 2)) > + continue; > + code = ((u64)code64[0] << 32) | code64[1]; > + > + } else if (cells == 4) { > + if (of_property_read_u32_array(child, "event_code", code128, 4)) > + continue; > + code = ((u64)code128[1] << 32) | code128[3]; > + > + } else { > + pr_warn("pmu_dts: invalid event_code for %s\n", child->name); > + continue; > + } > + > + evt = kzalloc(sizeof(*evt), GFP_KERNEL); > + if (!evt) > + continue; > + > + snprintf(evt->name, sizeof(evt->name), "%s", child->name); > + snprintf(evt->config, sizeof(evt->config), "event=0x%llx", code); > + > + sysfs_attr_init(&evt->attr.attr); > + evt->attr.attr.name = evt->name; > + evt->attr.attr.mode = 0444; > + evt->attr.show = pmu_dts_event_show; > + dts_events[dts_event_count] = evt; > + pmu_dts_events_attrs[dts_event_count] = &evt->attr.attr; > + dts_event_count++; > + > + if (dts_event_count >= MAX_DTS_EVENTS) > + break; And node cleanup? > + } > + pmu_dts_events_attrs[dts_event_count] = NULL; > + > + /* Register PMU */ No. > + pr_info("pmu_dts: registering PMU\n"); No. > + return register_power_pmu(&dts_pmu); > +} > + > +/* Platform driver */ This is ridicilous comment. > +static struct platform_driver pmu_dts_driver = { > + .probe = pmu_dts_probe, > + .driver = { > + .name = "pmu_dts", > + .of_match_table = pmu_dts_of_match, > + }, > +}; > + > +static int __init pmu_dts_init(void) > +{ > + pr_info("pmu_dts: init\n"); NAK, init functions do not print anything. RFC does not mean you can send debugging code with poor quality and... > + return platform_driver_register(&pmu_dts_driver); > +} > + > +static void __exit pmu_dts_exit(void) > +{ > + pr_info("pmu_dts: exit\n"); > + platform_driver_unregister(&pmu_dts_driver); > + unregister_power_pmu(&dts_pmu); > +} > +module_init(pmu_dts_init); > +module_exit(pmu_dts_exit); > + > +MODULE_LICENSE("GPL"); > +MODULE_AUTHOR("Shivani Nittor"); > +MODULE_DESCRIPTION("PMU DTS driver"); > diff --git a/arch/powerpc/perf/internal.h b/arch/powerpc/perf/internal.h > index a70ac471a5a5..11154ee31f8e 100644 > --- a/arch/powerpc/perf/internal.h > +++ b/arch/powerpc/perf/internal.h > @@ -2,6 +2,7 @@ > // > // Copyright 2019 Madhavan Srinivasan, IBM Corporation. > > +void unregister_power_pmu(struct power_pmu *pmu); > int __init init_ppc970_pmu(void); > int __init init_power5_pmu(void); > int __init init_power5p_pmu(void); > diff --git a/arch/powerpc/perf/isa207-common.c b/arch/powerpc/perf/isa207-common.c > index 2b3547fdba4a..e11d1bbbc27b 100644 > --- a/arch/powerpc/perf/isa207-common.c > +++ b/arch/powerpc/perf/isa207-common.c > @@ -7,6 +7,7 @@ > * Copyright 2016 Madhavan Srinivasan, IBM Corporation. > */ > #include "isa207-common.h" > +#include > > PMU_FORMAT_ATTR(event, "config:0-49"); > PMU_FORMAT_ATTR(pmcxsel, "config:0-7"); > diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c > index 1946dbdc9fa1..35be67eef2c6 100644 > --- a/arch/powerpc/platforms/powernv/opal.c > +++ b/arch/powerpc/platforms/powernv/opal.c > @@ -947,6 +947,18 @@ static void __init opal_imc_init_dev(void) > > of_node_put(np); > } > +#define PMU_DTB "ibm,power-pmu" > + > +static void __init opal_pmus_init_dev(void) > +{ > + struct device_node *np; > + > + np = of_find_compatible_node(NULL, NULL, PMU_DTB); > + if (np) > + of_platform_device_create(np, NULL, NULL); > + > + of_node_put(np); > +} > > static int kopald(void *unused) > { > @@ -1032,6 +1044,9 @@ static int __init opal_init(void) > /* Detect In-Memory Collection counters and create devices*/ > opal_imc_init_dev(); > > + /*Detect PMU node and create device*/ .... with completely broken indentation style. > + opal_pmus_init_dev(); > + > /* Create leds platform devices */ > leds = of_find_node_by_path("/ibm,opal/leds"); > if (leds) { Best regards, Krzysztof