stmmac: export DMA TX/RX rings via debugfs (v3)

This patch adds the following debugFs entry to dump the
RX/TX DMA rings:

/sys/kernel/debug/stmmaceth/descriptors_status

This is an example:

=======================
  RX descriptor ring
=======================
[0] DES0=0x85ee0320 DES1=0x1fff1fff BUF1=0x5fae2022 BUF2=0x0
[1] DES0=0x85ee0320 DES1=0x1fff1fff BUF1=0x5fae0022 BUF2=0x0
[2] DES0=0x81460320 DES1=0x1fff1fff BUF1=0x5f9dd022 BUF2=0x0

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 112 insertions, 0 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/Kconfig b/drivers/net/ethernet/stmicro/stmmac/Kconfig
index cda61e37c357..ae7f56312f08 100644
--- a/drivers/net/ethernet/stmicro/stmmac/Kconfig
+++ b/drivers/net/ethernet/stmicro/stmmac/Kconfig
@@ -11,6 +11,13 @@ config STMMAC_ETH
 
 if STMMAC_ETH
 
+config STMMAC_DEBUG_FS
+        bool "Enable monitoring via sysFS "
+        default n
+        depends on STMMAC_ETH && DEBUG_FS
+        -- help
+          The stmmac entry in /sys reports DMA TX/RX rings.
+
 config STMMAC_DA
         bool "STMMAC DMA arbitration scheme"
         default n
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index c28b90d35007..caaad7b14621 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -48,6 +48,10 @@
 #include <linux/slab.h>
 #include <linux/prefetch.h>
 #include "stmmac.h"
+#ifdef CONFIG_STMMAC_DEBUG_FS
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#endif
 
 #define STMMAC_RESOURCE_NAME    "stmmaceth"
 
@@ -1425,6 +1429,96 @@ static int stmmac_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
         return ret;
 }
 
+#ifdef CONFIG_STMMAC_DEBUG_FS
+static struct dentry *stmmac_fs_dir;
+static struct dentry *stmmac_rings_status;
+
+static int stmmac_sysfs_ring_read(struct seq_file *seq, void *v)
+{
+        struct tmp_s {
+                u64 a;
+                unsigned int b;
+                unsigned int c;
+        };
+        int i;
+        struct net_device *dev = seq->private;
+        struct stmmac_priv *priv = netdev_priv(dev);
+
+        seq_printf(seq, "=======================\n");
+        seq_printf(seq, " RX descriptor ring\n");
+        seq_printf(seq, "=======================\n");
+
+        for (i = 0; i < priv->dma_rx_size; i++) {
+                struct tmp_s *x = (struct tmp_s *)(priv->dma_rx + i);
+                seq_printf(seq, "[%d] DES0=0x%x DES1=0x%x BUF1=0x%x BUF2=0x%x",
+                           i, (unsigned int)(x->a),
+                           (unsigned int)((x->a) >> 32), x->b, x->c);
+                seq_printf(seq, "\n");
+        }
+
+        seq_printf(seq, "\n");
+        seq_printf(seq, "=======================\n");
+        seq_printf(seq, "  TX descriptor ring\n");
+        seq_printf(seq, "=======================\n");
+
+        for (i = 0; i < priv->dma_tx_size; i++) {
+                struct tmp_s *x = (struct tmp_s *)(priv->dma_tx + i);
+                seq_printf(seq, "[%d] DES0=0x%x DES1=0x%x BUF1=0x%x BUF2=0x%x",
+                           i, (unsigned int)(x->a),
+                           (unsigned int)((x->a) >> 32), x->b, x->c);
+                seq_printf(seq, "\n");
+        }
+
+        return 0;
+}
+
+static int stmmac_sysfs_ring_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, stmmac_sysfs_ring_read, inode->i_private);
+}
+
+static const struct file_operations stmmac_rings_status_fops = {
+        .owner = THIS_MODULE,
+        .open = stmmac_sysfs_ring_open,
+        .read = seq_read,
+        .llseek = seq_lseek,
+        .release = seq_release,
+};
+
+static int stmmac_init_fs(struct net_device *dev)
+{
+        /* Create debugfs entries */
+        stmmac_fs_dir = debugfs_create_dir(STMMAC_RESOURCE_NAME, NULL);
+
+        if (!stmmac_fs_dir || IS_ERR(stmmac_fs_dir)) {
+                pr_err("ERROR %s, debugfs create directory failed\n",
+                       STMMAC_RESOURCE_NAME);
+
+                return -ENOMEM;
+        }
+
+        /* Entry to report DMA RX/TX rings */
+        stmmac_rings_status = debugfs_create_file("descriptors_status",
+                                           S_IRUGO, stmmac_fs_dir, dev,
+                                           &stmmac_rings_status_fops);
+
+        if (!stmmac_rings_status || IS_ERR(stmmac_rings_status)) {
+                pr_info("ERROR creating stmmac ring debugfs file\n");
+                debugfs_remove(stmmac_fs_dir);
+
+                return -ENOMEM;
+        }
+
+        return 0;
+}
+
+static void stmmac_exit_fs(void)
+{
+        debugfs_remove(stmmac_rings_status);
+        debugfs_remove(stmmac_fs_dir);
+}
+#endif /* CONFIG_STMMAC_DEBUG_FS */
+
 static const struct net_device_ops stmmac_netdev_ops = {
         .ndo_open = stmmac_open,
         .ndo_start_xmit = stmmac_xmit,
@@ -1651,6 +1745,13 @@ static int stmmac_dvr_probe(struct platform_device *pdev)
         if (ret < 0)
                 goto out_unregister;
         pr_debug("registered!\n");
+
+#ifdef CONFIG_STMMAC_DEBUG_FS
+        ret = stmmac_init_fs(ndev);
+        if (ret < 0)
+                pr_warning("\tFailed debugFS registration");
+#endif
+
         return 0;
 
 out_unregister:
@@ -1703,6 +1804,10 @@ static int stmmac_dvr_remove(struct platform_device *pdev)
         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
         release_mem_region(res->start, resource_size(res));
 
+#ifdef CONFIG_STMMAC_DEBUG_FS
+        stmmac_exit_fs();
+#endif
+
         free_netdev(ndev);
 
         return 0;