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Message-ID: <b76aaf39-1a03-ffbf-ae44-66dd01753bc7@linux.intel.com>
Date: Mon, 24 Mar 2025 15:01:49 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
Krzysztof Wilczyński <kw@...ux.com>,
Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
Jingoo Han <jingoohan1@...il.com>, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 1/3] PCI: Add sysfs support for exposing PTM context
On Mon, 24 Mar 2025, Manivannan Sadhasivam via B4 Relay wrote:
> From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>
> Precision Time Management (PTM) mechanism defined in PCIe spec r6.0,
> sec 6.22 allows precise coordination of timing information across multiple
> components in a PCIe hierarchy with independent local time clocks.
Hi Mani,
PCIe r6.0.1 sec 6.22 is about Readiness Notification (RN) and PTM is 6.21,
did you perhaps mistype the section number?
> PCI core already supports enabling PTM in the root port and endpoint
> devices through PTM Extended Capability registers. But the PTM context
> supported by the PTM capable components such as Root Complex (RC) and
> Endpoint (EP) controllers were not exposed as of now.
>
> Hence, add the sysfs support to expose the PTM context to userspace from
> both PCIe RC and EP controllers. Controller drivers are expected to call
> pcie_ptm_create_sysfs() to create the sysfs attributes for the PTM context
> and call pcie_ptm_destroy_sysfs() to destroy them. The drivers should also
> populate the relevant callbacks in the 'struct pcie_ptm_ops' structure
> based on the controller implementation.
>
> Below PTM context are exposed through sysfs:
>
> PCIe RC
> =======
>
> 1. PTM Local clock
> 2. PTM T2 timestamp
> 3. PTM T3 timestamp
> 4. PTM Context valid
>
> PCIe EP
> =======
>
> 1. PTM Local clock
> 2. PTM T1 timestamp
> 3. PTM T4 timestamp
> 4. PTM Master clock
> 5. PTM Context update
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
> Documentation/ABI/testing/sysfs-platform-pcie-ptm | 70 ++++++
> MAINTAINERS | 1 +
> drivers/pci/pcie/ptm.c | 268 ++++++++++++++++++++++
> include/linux/pci.h | 35 +++
> 4 files changed, 374 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-platform-pcie-ptm b/Documentation/ABI/testing/sysfs-platform-pcie-ptm
> new file mode 100644
> index 0000000000000000000000000000000000000000..010c3e32e2b8eaf352a8e1aad7420d8a3e948dae
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-platform-pcie-ptm
> @@ -0,0 +1,70 @@
> +What: /sys/devices/platform/*/ptm/local_clock
> +Date: February 2025
> +Contact: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +Description:
> + (RO) PTM local clock in nanoseconds. Applicable for both Root
> + Complex and Endpoint controllers.
> +
> +What: /sys/devices/platform/*/ptm/master_clock
> +Date: February 2025
> +Contact: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +Description:
> + (RO) PTM master clock in nanoseconds. Applicable only for
> + Endpoint controllers.
> +
> +What: /sys/devices/platform/*/ptm/t1
> +Date: February 2025
> +Contact: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +Description:
> + (RO) PTM T1 timestamp in nanoseconds. Applicable only for
> + Endpoint controllers.
> +
> +What: /sys/devices/platform/*/ptm/t2
> +Date: February 2025
> +Contact: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +Description:
> + (RO) PTM T2 timestamp in nanoseconds. Applicable only for
> + Root Complex controllers.
> +
> +What: /sys/devices/platform/*/ptm/t3
> +Date: February 2025
> +Contact: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +Description:
> + (RO) PTM T3 timestamp in nanoseconds. Applicable only for
> + Root Complex controllers.
> +
> +What: /sys/devices/platform/*/ptm/t4
> +Date: February 2025
> +Contact: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +Description:
> + (RO) PTM T4 timestamp in nanoseconds. Applicable only for
> + Endpoint controllers.
> +
> +What: /sys/devices/platform/*/ptm/context_update
> +Date: February 2025
> +Contact: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +Description:
> + (RW) Control the PTM context update mode. Applicable only for
> + Endpoint controllers.
> +
> + Following values are supported:
> +
> + * auto = PTM context auto update trigger for every 10ms
> +
> + * manual = PTM context manual update. Writing 'manual' to this
> + file triggers PTM context update (default)
> +
> +What: /sys/devices/platform/*/ptm/context_valid
> +Date: February 2025
> +Contact: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +Description:
> + (RW) Control the PTM context validity (local clock timing).
> + Applicable only for Root Complex controllers. PTM context is
> + invalidated by hardware if the Root Complex enters low power
> + mode or changes link frequency.
> +
> + Following values are supported:
> +
> + * 0 = PTM context invalid (default)
> +
> + * 1 = PTM context valid
> diff --git a/MAINTAINERS b/MAINTAINERS
> index b4d09d52a750b320f689c1365791cdfa6e719fde..f1bac092877df739328347481bd14f6701a7df19 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -18213,6 +18213,7 @@ Q: https://patchwork.kernel.org/project/linux-pci/list/
> B: https://bugzilla.kernel.org
> C: irc://irc.oftc.net/linux-pci
> T: git git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
> +F: Documentation/ABI/testing/sysfs-platform-pcie-ptm
> F: Documentation/devicetree/bindings/pci/
> F: drivers/pci/controller/
> F: drivers/pci/pci-bridge-emul.c
> diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
> index 7cfb6c0d5dcb6de2a759b56d6877c95102b3d10f..bfa632b76a87ad304e966a8edfb5dba14d58a23c 100644
> --- a/drivers/pci/pcie/ptm.c
> +++ b/drivers/pci/pcie/ptm.c
> @@ -10,6 +10,8 @@
> #include <linux/pci.h>
> #include "../pci.h"
>
> +struct device *ptm_device;
> +
> /*
> * If the next upstream device supports PTM, return it; otherwise return
> * NULL. PTM Messages are local, so both link partners must support it.
> @@ -252,3 +254,269 @@ bool pcie_ptm_enabled(struct pci_dev *dev)
> return dev->ptm_enabled;
> }
> EXPORT_SYMBOL(pcie_ptm_enabled);
> +
> +static ssize_t context_update_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> + int ret;
> +
> + if (!ptm->ops->context_update_store)
> + return -EOPNOTSUPP;
> +
> + ret = ptm->ops->context_update_store(ptm->pdata, buf);
Do these store funcs need some locking? Who is responsible about it?
Why isn't buf parsed here and converted to some define/enum values, what
is the advantage of passing it on as char *?
--
i.
> + if (ret)
> + return ret;
> +
> + return count;
> +}
> +
> +static ssize_t context_update_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> +
> + if (!ptm->ops->context_update_show)
> + return -EOPNOTSUPP;
> +
> + return ptm->ops->context_update_show(ptm->pdata, buf);
> +}
> +
> +static ssize_t context_valid_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> + unsigned long arg;
> + int ret;
> +
> + if (kstrtoul(buf, 0, &arg) < 0)
> + return -EINVAL;
> +
> + if (!ptm->ops->context_valid_store)
> + return -EOPNOTSUPP;
> +
> + ret = ptm->ops->context_valid_store(ptm->pdata, !!arg);
> + if (ret)
> + return ret;
> +
> + return count;
> +}
> +
> +static ssize_t context_valid_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> +
> + if (!ptm->ops->context_valid_show)
> + return -EOPNOTSUPP;
> +
> + return ptm->ops->context_valid_show(ptm->pdata, buf);
> +}
> +
> +static ssize_t local_clock_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> +
> + if (!ptm->ops->local_clock_show)
> + return -EOPNOTSUPP;
> +
> + return ptm->ops->local_clock_show(ptm->pdata, buf);
> +}
> +
> +static ssize_t master_clock_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> +
> + if (!ptm->ops->master_clock_show)
> + return -EOPNOTSUPP;
> +
> + return ptm->ops->master_clock_show(ptm->pdata, buf);
> +}
> +
> +static ssize_t t1_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> +
> + if (!ptm->ops->t1_show)
> + return -EOPNOTSUPP;
> +
> + return ptm->ops->t1_show(ptm->pdata, buf);
> +}
> +
> +static ssize_t t2_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> +
> + if (!ptm->ops->t2_show)
> + return -EOPNOTSUPP;
> +
> + return ptm->ops->t2_show(ptm->pdata, buf);
> +}
> +
> +static ssize_t t3_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> +
> + if (!ptm->ops->t3_show)
> + return -EOPNOTSUPP;
> +
> + return ptm->ops->t3_show(ptm->pdata, buf);
> +}
> +
> +static ssize_t t4_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> +
> + if (!ptm->ops->t4_show)
> + return -EOPNOTSUPP;
> +
> + return ptm->ops->t4_show(ptm->pdata, buf);
> +}
> +
> +static DEVICE_ATTR_RW(context_update);
> +static DEVICE_ATTR_RW(context_valid);
> +static DEVICE_ATTR_RO(local_clock);
> +static DEVICE_ATTR_RO(master_clock);
> +static DEVICE_ATTR_RO(t1);
> +static DEVICE_ATTR_RO(t2);
> +static DEVICE_ATTR_RO(t3);
> +static DEVICE_ATTR_RO(t4);
> +
> +static struct attribute *pcie_ptm_attrs[] = {
> + &dev_attr_context_update.attr,
> + &dev_attr_context_valid.attr,
> + &dev_attr_local_clock.attr,
> + &dev_attr_master_clock.attr,
> + &dev_attr_t1.attr,
> + &dev_attr_t2.attr,
> + &dev_attr_t3.attr,
> + &dev_attr_t4.attr,
> + NULL
> +};
> +
> +static umode_t pcie_ptm_attr_visible(struct kobject *kobj, struct attribute *attr,
> + int n)
> +{
> + struct device *dev = container_of(kobj, struct device, kobj);
> + struct pcie_ptm *ptm = dev_get_drvdata(dev);
> +
> + if ((attr == &dev_attr_t1.attr && ptm->ops->t1_visible &&
> + ptm->ops->t1_visible(ptm->pdata)) ||
> + (attr == &dev_attr_t2.attr && ptm->ops->t2_visible &&
> + ptm->ops->t2_visible(ptm->pdata)) ||
> + (attr == &dev_attr_t3.attr && ptm->ops->t3_visible &&
> + ptm->ops->t3_visible(ptm->pdata)) ||
> + (attr == &dev_attr_t4.attr && ptm->ops->t4_visible &&
> + ptm->ops->t4_visible(ptm->pdata)) ||
> + (attr == &dev_attr_local_clock.attr &&
> + ptm->ops->local_clock_visible &&
> + ptm->ops->local_clock_visible(ptm->pdata)) ||
> + (attr == &dev_attr_master_clock.attr &&
> + ptm->ops->master_clock_visible &&
> + ptm->ops->master_clock_visible(ptm->pdata)) ||
> + (attr == &dev_attr_context_update.attr &&
> + ptm->ops->context_update_visible &&
> + ptm->ops->context_update_visible(ptm->pdata)) ||
> + (attr == &dev_attr_context_valid.attr &&
> + ptm->ops->context_valid_visible &&
> + ptm->ops->context_valid_visible(ptm->pdata)))
> + return attr->mode;
> +
> + return 0;
> +}
> +
> +static const struct attribute_group pcie_ptm_attr_group = {
> + .attrs = pcie_ptm_attrs,
> + .is_visible = pcie_ptm_attr_visible,
> +};
> +
> +static const struct attribute_group *pcie_ptm_attr_groups[] = {
> + &pcie_ptm_attr_group,
> + NULL,
> +};
> +
> +static void pcie_ptm_release(struct device *dev)
> +{
> + struct pcie_ptm *ptm = container_of(dev, struct pcie_ptm, dev);
> +
> + kfree(ptm);
> +}
> +
> +/*
> + * pcie_ptm_create_sysfs() - Create sysfs entries for the PTM context
> + * @dev: PTM capable component device
> + * @pdata: Private data of the PTM capable component device
> + * @ops: PTM callback structure
> + *
> + * Create sysfs entries for exposing the PTM context of the PTM capable
> + * components such as Root Complex and Endpoint controllers.
> + */
> +int pcie_ptm_create_sysfs(struct device *dev, void *pdata,
> + struct pcie_ptm_ops *ops)
> +{
> + struct pcie_ptm *ptm;
> + int ret;
> +
> + /* Caller must provide check_capability() callback */
> + if (!ops->check_capability)
> + return -EINVAL;
> +
> + /* Check for PTM capability before creating sysfs attrbutes */
> + ret = ops->check_capability(pdata);
> + if (!ret) {
> + dev_dbg(dev, "PTM capability not present\n");
> + return -ENODATA;
> + }
> +
> + ptm = kzalloc(sizeof(*ptm), GFP_KERNEL);
> + if (!ptm)
> + return -ENOMEM;
> +
> + ptm->pdata = pdata;
> + ptm->ops = ops;
> +
> + device_initialize(&ptm->dev);
> + ptm->dev.groups = pcie_ptm_attr_groups;
> + ptm->dev.release = pcie_ptm_release;
> + ptm->dev.parent = dev;
> + dev_set_drvdata(&ptm->dev, ptm);
> + device_set_pm_not_required(&ptm->dev);
> +
> + ret = dev_set_name(&ptm->dev, "ptm");
> + if (ret)
> + goto err_put_device;
> +
> + ret = device_add(&ptm->dev);
> + if (ret)
> + goto err_put_device;
> +
> + ptm_device = &ptm->dev;
> +
> + return 0;
> +
> +err_put_device:
> + put_device(&ptm->dev);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(pci_ptm_init);
> +
> +/*
> + * pcie_ptm_destroy_sysfs() - Destroy sysfs entries for the PTM context
> + */
> +void pcie_ptm_destroy_sysfs(void)
> +{
> + if (ptm_device) {
> + device_unregister(ptm_device);
> + ptm_device = NULL;
> + }
> +}
> +EXPORT_SYMBOL(pcie_ptm_destroy_sysfs);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 47b31ad724fa5bf7abd7c3dc572947551b0f2148..42bb3cf0212e96fd65a1f01410ef70c82491c9eb 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1857,16 +1857,51 @@ static inline bool pci_aer_available(void) { return false; }
>
> bool pci_ats_disabled(void);
>
> +struct pcie_ptm_ops {
> + int (*check_capability)(void *drvdata);
> + int (*context_update_store)(void *drvdata, const char *buf);
> + ssize_t (*context_update_show)(void *drvdata, char *buf);
> + int (*context_valid_store)(void *drvdata, bool valid);
> + ssize_t (*context_valid_show)(void *drvdata, char *buf);
> + ssize_t (*local_clock_show)(void *drvdata, char *buf);
> + ssize_t (*master_clock_show)(void *drvdata, char *buf);
> + ssize_t (*t1_show)(void *drvdata, char *buf);
> + ssize_t (*t2_show)(void *drvdata, char *buf);
> + ssize_t (*t3_show)(void *drvdata, char *buf);
> + ssize_t (*t4_show)(void *drvdata, char *buf);
> +
> + bool (*context_update_visible)(void *drvdata);
> + bool (*context_valid_visible)(void *drvdata);
> + bool (*local_clock_visible)(void *drvdata);
> + bool (*master_clock_visible)(void *drvdata);
> + bool (*t1_visible)(void *drvdata);
> + bool (*t2_visible)(void *drvdata);
> + bool (*t3_visible)(void *drvdata);
> + bool (*t4_visible)(void *drvdata);
> +};
> +
> +struct pcie_ptm {
> + struct device dev;
> + struct pcie_ptm_ops *ops;
> + void *pdata;
> +};
> +
> #ifdef CONFIG_PCIE_PTM
> int pci_enable_ptm(struct pci_dev *dev, u8 *granularity);
> void pci_disable_ptm(struct pci_dev *dev);
> bool pcie_ptm_enabled(struct pci_dev *dev);
> +int pcie_ptm_create_sysfs(struct device *dev, void *pdata, struct pcie_ptm_ops *ops);
> +void pcie_ptm_destroy_sysfs(void);
> #else
> static inline int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
> { return -EINVAL; }
> static inline void pci_disable_ptm(struct pci_dev *dev) { }
> static inline bool pcie_ptm_enabled(struct pci_dev *dev)
> { return false; }
> +static inline int pcie_ptm_create_sysfs(struct device *dev, void *pdata,
> + struct pcie_ptm_ops *ops)
> +{ return 0; }
> +static inline void pcie_ptm_destroy_sysfs(void) { }
> #endif
>
> void pci_cfg_access_lock(struct pci_dev *dev);
>
>
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