linux-kernel - [PATCH 1/9] PCI: sysfs: Export available PCIe bandwidth

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Message-Id: <20180903180242.14504-2-mr.nuke.me@gmail.com>
Date:   Mon,  3 Sep 2018 13:02:28 -0500
From:   Alexandru Gagniuc <mr.nuke.me@...il.com>
To:     linux-pci@...r.kernel.org, bhelgaas@...gle.com
Cc:     keith.busch@...el.com, alex_gagniuc@...lteam.com,
        austin_bolen@...l.com, shyam_iyer@...l.com,
        Alexandru Gagniuc <mr.nuke.me@...il.com>,
        Ariel Elior <ariel.elior@...ium.com>,
        everest-linux-l2@...ium.com,
        "David S. Miller" <davem@...emloft.net>,
        Michael Chan <michael.chan@...adcom.com>,
        Ganesh Goudar <ganeshgr@...lsio.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Leon Romanovsky <leon@...nel.org>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Dirk van der Merwe <dirk.vandermerwe@...ronome.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, linux-rdma@...r.kernel.org,
        oss-drivers@...ronome.com
Subject: [PATCH 1/9] PCI: sysfs: Export available PCIe bandwidth

For certain bandwidth-critical devices (e.g. multi-port network cards)
it is useful to know the available bandwidth to the root complex. This
information is only available via the system log, which doesn't
account for link degradation after probing.

With a sysfs attribute, we can computes the bandwidth on-demand, and
will detect degraded links.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...il.com>
---
 drivers/pci/pci-sysfs.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 9ecfe13157c0..6658e927b1f5 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -218,6 +218,18 @@ static ssize_t current_link_width_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(current_link_width);
 
+static ssize_t available_bandwidth_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	struct pci_dev *pci_dev = to_pci_dev(dev);
+	u32 bw_avail;
+
+	bw_avail = pcie_bandwidth_available(pci_dev, NULL, NULL, NULL);
+
+	return sprintf(buf, "%u.%03u Gb/s\n", bw_avail / 1000, bw_avail % 1000);
+}
+static DEVICE_ATTR_RO(available_bandwidth);
+
 static ssize_t secondary_bus_number_show(struct device *dev,
 					 struct device_attribute *attr,
 					 char *buf)
@@ -786,6 +798,7 @@ static struct attribute *pcie_dev_attrs[] = {
 	&dev_attr_current_link_width.attr,
 	&dev_attr_max_link_width.attr,
 	&dev_attr_max_link_speed.attr,
+	&dev_attr_available_bandwidth.attr,
 	NULL,
 };
 
-- 
2.17.1