[Linux-kernel-mentees] [PATCH v1] PCI: Add support for LTR

[Linux-kernel-mentees] [PATCH v1] PCI: Add support for LTR

[Puranjay Mohan]

Add a new function pci_ltr_init() which will be called from
pci_init_capabilities() to initialize every PCIe device's LTR values.
Add code in probe.c to evaluate LTR _DSM and save the latencies in pci_dev.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
---
v1 - based the patch on v5.9-rc1 so it applies correctly
---
 drivers/pci/pci-acpi.c   | 28 ++++++++++++++++++++++++++++
 drivers/pci/pci.c        | 27 +++++++++++++++++++++++++++
 drivers/pci/pci.h        |  5 +++++
 drivers/pci/probe.c      |  6 ++++++
 include/linux/pci-acpi.h |  1 +
 include/linux/pci.h      |  2 ++
 6 files changed, 69 insertions(+)

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index d5869a03f748..c77e47b53751 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -1213,6 +1213,34 @@ static void pci_acpi_optimize_delay(struct pci_dev *pdev,
 	ACPI_FREE(obj);
 }
 
+/* pci_acpi_evaluate_ltr_latency
+ *
+ * @dev - the pci_dev to evaluate and save latencies
+ */
+void pci_acpi_evaluate_ltr_latency(struct pci_dev *dev)
+{
+	union acpi_object *obj, *elements;
+	struct acpi_device *handle;
+
+	handle = ACPI_HANDLE(&dev->dev);
+	if (!handle)
+		return;
+
+	obj = acpi_evaluate_dsm(handle, &pci_acpi_dsm_guid, 0x2,
+				DSM_PCI_LTR_MAX_LATENCY, NULL);
+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 4) {
+		elements = obj->package.elements;
+		dev->max_snoop_latency = (u16)elements[1].integer.value |
+				((u16)elements[0].integer.value << PCI_LTR_SCALE_SHIFT);
+		dev->max_nosnoop_latency = (u16)elements[3].integer.value |
+				((u16)elements[2].integer.value << PCI_LTR_SCALE_SHIFT);
+	}
+	ACPI_FREE(obj);
+}
+
 static void pci_acpi_set_external_facing(struct pci_dev *dev)
 {
 	u8 val;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index a458c46d7e39..b5531272b865 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3056,6 +3056,33 @@ void pci_pm_init(struct pci_dev *dev)
 		dev->imm_ready = 1;
 }
 
+/**
+ * pci_ltr_init - Initialize Latency Tolerance Information of given PCI device
+ * @dev: PCI device to handle.
+ */
+void pci_ltr_init(struct pci_dev *dev)
+{
+#ifdef CONFIG_PCIASPM
+	int ltr;
+	struct pci_dev *endpoint_dev = dev;
+	u16 max_snoop_sum = 0;
+	u16 max_nosnoop_sum = 0;
+
+	ltr = pci_find_ext_capability(endpoint_dev, PCI_EXT_CAP_ID_LTR);
+	if (!ltr)
+		return;
+
+	dev = pci_upstream_bridge(dev);
+	while (dev) {
+		max_snoop_sum += dev->max_snoop_latency;
+		max_nosnoop_sum += dev->max_nosnoop_latency;
+		dev = pci_upstream_bridge(dev);
+	}
+	pci_write_config_word(endpoint_dev, ltr + PCI_LTR_MAX_SNOOP_LAT, max_snoop_sum);
+	pci_write_config_word(endpoint_dev, ltr + PCI_LTR_MAX_NOSNOOP_LAT, max_nosnoop_sum);
+#endif
+}
+
 static unsigned long pci_ea_flags(struct pci_dev *dev, u8 prop)
 {
 	unsigned long flags = IORESOURCE_PCI_FIXED | IORESOURCE_PCI_EA_BEI;
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index fa12f7cbc1a0..ef3d22b82200 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -110,6 +110,7 @@ void pci_free_cap_save_buffers(struct pci_dev *dev);
 bool pci_bridge_d3_possible(struct pci_dev *dev);
 void pci_bridge_d3_update(struct pci_dev *dev);
 void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev);
+void pci_ltr_init(struct pci_dev *dev);
 
 static inline void pci_wakeup_event(struct pci_dev *dev)
 {
@@ -680,11 +681,15 @@ static inline int pci_aer_raw_clear_status(struct pci_dev *dev) { return -EINVAL
 
 #ifdef CONFIG_ACPI
 int pci_acpi_program_hp_params(struct pci_dev *dev);
+void pci_acpi_evaluate_ltr_latency(struct pci_dev *dev);
 #else
 static inline int pci_acpi_program_hp_params(struct pci_dev *dev)
 {
 	return -ENODEV;
 }
+static inline void pci_acpi_evaluate_ltr_latency(struct pci_dev *dev)
+{
+}
 #endif
 
 #ifdef CONFIG_PCIEASPM
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 03d37128a24f..0257aa615665 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2140,6 +2140,11 @@ static void pci_configure_ltr(struct pci_dev *dev)
 		dev->ltr_path = 1;
 	}
 #endif
+
+	/*
+	 * Read latency values from _DSM and save in pci_dev
+	 */
+	pci_acpi_evaluate_ltr_latency(dev);
 }
 
 static void pci_configure_eetlp_prefix(struct pci_dev *dev)
@@ -2400,6 +2405,7 @@ static void pci_init_capabilities(struct pci_dev *dev)
 	pci_ptm_init(dev);		/* Precision Time Measurement */
 	pci_aer_init(dev);		/* Advanced Error Reporting */
 	pci_dpc_init(dev);		/* Downstream Port Containment */
+	pci_ltr_init(dev);		/* Latency Tolerance Reporting */
 
 	pcie_report_downtraining(dev);
 
diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
index 5ba475ca9078..e23236a4ff66 100644
--- a/include/linux/pci-acpi.h
+++ b/include/linux/pci-acpi.h
@@ -110,6 +110,7 @@ extern const guid_t pci_acpi_dsm_guid;
 
 /* _DSM Definitions for PCI */
 #define DSM_PCI_PRESERVE_BOOT_CONFIG		0x05
+#define DSM_PCI_LTR_MAX_LATENCY			0x06
 #define DSM_PCI_DEVICE_NAME			0x07
 #define DSM_PCI_POWER_ON_RESET_DELAY		0x08
 #define DSM_PCI_DEVICE_READINESS_DURATIONS	0x09
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 835530605c0d..9de6b290ed81 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -380,6 +380,8 @@ struct pci_dev {
 	struct pcie_link_state	*link_state;	/* ASPM link state */
 	unsigned int	ltr_path:1;	/* Latency Tolerance Reporting
 					   supported from root to here */
+	u16 max_snoop_latency;		/* LTR Max Snoop latency */
+	u16 max_nosnoop_latency;	/* LTR Max No Snoop latency */
 #endif
 	unsigned int	eetlp_prefix_path:1;	/* End-to-End TLP Prefix */
 
-- 
2.27.0

_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

Re: [Linux-kernel-mentees] [PATCH v1] PCI: Add support for LTR

[kernel test robot]

[-- Attachment #1: Type: text/plain, Size: 3107 bytes --]

Hi Puranjay,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on pci/next]
[also build test ERROR on pm/linux-next v5.9-rc2 next-20200825]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Puranjay-Mohan/PCI-Add-support-for-LTR/20200825-014435
base:   https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git next
config: x86_64-randconfig-r022-20200825 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 77e5a195f818b9ace91f7b12ab948b21d7918238)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> drivers/pci/pci-acpi.c:1236:8: error: no member named 'max_snoop_latency' in 'struct pci_dev'
                   dev->max_snoop_latency = (u16)elements[1].integer.value |
                   ~~~  ^
>> drivers/pci/pci-acpi.c:1238:8: error: no member named 'max_nosnoop_latency' in 'struct pci_dev'
                   dev->max_nosnoop_latency = (u16)elements[3].integer.value |
                   ~~~  ^
   2 errors generated.

# https://github.com/0day-ci/linux/commit/fa2179400e50db2342c6d6445c8805a773ec9dc9
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Puranjay-Mohan/PCI-Add-support-for-LTR/20200825-014435
git checkout fa2179400e50db2342c6d6445c8805a773ec9dc9
vim +1236 drivers/pci/pci-acpi.c

  1215	
  1216	/* pci_acpi_evaluate_ltr_latency
  1217	 *
  1218	 * @dev - the pci_dev to evaluate and save latencies
  1219	 */
  1220	void pci_acpi_evaluate_ltr_latency(struct pci_dev *dev)
  1221	{
  1222		union acpi_object *obj, *elements;
  1223		struct acpi_device *handle;
  1224	
  1225		handle = ACPI_HANDLE(&dev->dev);
  1226		if (!handle)
  1227			return;
  1228	
  1229		obj = acpi_evaluate_dsm(handle, &pci_acpi_dsm_guid, 0x2,
  1230					DSM_PCI_LTR_MAX_LATENCY, NULL);
  1231		if (!obj)
  1232			return;
  1233	
  1234		if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 4) {
  1235			elements = obj->package.elements;
> 1236			dev->max_snoop_latency = (u16)elements[1].integer.value |
  1237					((u16)elements[0].integer.value << PCI_LTR_SCALE_SHIFT);
> 1238			dev->max_nosnoop_latency = (u16)elements[3].integer.value |
  1239					((u16)elements[2].integer.value << PCI_LTR_SCALE_SHIFT);
  1240		}
  1241		ACPI_FREE(obj);
  1242	}
  1243	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 29189 bytes --]

[-- Attachment #3: Type: text/plain, Size: 201 bytes --]

_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees