net: mvmdio: Avoid excessive sleeps in polled mode

[ Upstream commit 7dd12fe34686d89c332b1a05104d18d728591f0a ]

Before this change, when operating in polled mode, i.e. no IRQ is
available, every individual C45 access would be hit with a 150us sleep
after the bus access.

For example, on a board with a CN9130 SoC connected to an MV88X3310
PHY, a single C45 read would take around 165us:

    root@infix:~$ mdio f212a600.mdio-mii mmd 4:1 bench 0xc003
    Performed 1000 reads in 165ms

By replacing the long sleep with a tighter poll loop, we observe a 10x
increase in bus throughput:

    root@infix:~$ mdio f212a600.mdio-mii mmd 4:1 bench 0xc003
    Performed 1000 reads in 15ms

Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20231204100811.2708884-3-tobias@waldekranz.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/ethernet/marvell/mvmdio.c b/drivers/net/ethernet/marvell/mvmdio.c
index 6749131..2ef613a 100644 (file)
--- a/drivers/net/ethernet/marvell/mvmdio.c
+++ b/drivers/net/ethernet/marvell/mvmdio.c
@@ -23,6 +23,7 @@
 #include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/kernel.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
@@ -58,11 +59,6 @@
  * - Armada 370       (Globalscale Mirabox):   41us to 43us (Polled)
  */
 #define MVMDIO_SMI_TIMEOUT             1000 /* 1000us = 1ms */
-#define MVMDIO_SMI_POLL_INTERVAL_MIN   45
-#define MVMDIO_SMI_POLL_INTERVAL_MAX   55
-
-#define MVMDIO_XSMI_POLL_INTERVAL_MIN  150
-#define MVMDIO_XSMI_POLL_INTERVAL_MAX  160
 
 struct orion_mdio_dev {
        void __iomem *regs;
@@ -84,8 +80,6 @@ enum orion_mdio_bus_type {
 
 struct orion_mdio_ops {
        int (*is_done)(struct orion_mdio_dev *);
-       unsigned int poll_interval_min;
-       unsigned int poll_interval_max;
 };
 
 /* Wait for the SMI unit to be ready for another operation
@@ -94,34 +88,23 @@ static int orion_mdio_wait_ready(const struct orion_mdio_ops *ops,
                                 struct mii_bus *bus)
 {
        struct orion_mdio_dev *dev = bus->priv;
-       unsigned long timeout = usecs_to_jiffies(MVMDIO_SMI_TIMEOUT);
-       unsigned long end = jiffies + timeout;
-       int timedout = 0;
+       unsigned long timeout;
+       int done;
 
-       while (1) {
-               if (ops->is_done(dev))
+       if (dev->err_interrupt <= 0) {
+               if (!read_poll_timeout_atomic(ops->is_done, done, done, 2,
+                                             MVMDIO_SMI_TIMEOUT, false, dev))
+                       return 0;
+       } else {
+               /* wait_event_timeout does not guarantee a delay of at
+                * least one whole jiffie, so timeout must be no less
+                * than two.
+                */
+               timeout = max(usecs_to_jiffies(MVMDIO_SMI_TIMEOUT), 2);
+
+               if (wait_event_timeout(dev->smi_busy_wait,
+                                      ops->is_done(dev), timeout))
                        return 0;
-               else if (timedout)
-                       break;
-
-               if (dev->err_interrupt <= 0) {
-                       usleep_range(ops->poll_interval_min,
-                                    ops->poll_interval_max);
-
-                       if (time_is_before_jiffies(end))
-                               ++timedout;
-               } else {
-                       /* wait_event_timeout does not guarantee a delay of at
-                        * least one whole jiffie, so timeout must be no less
-                        * than two.
-                        */
-                       if (timeout < 2)
-                               timeout = 2;
-                       wait_event_timeout(dev->smi_busy_wait,
-                                          ops->is_done(dev), timeout);
-
-                       ++timedout;
-               }
        }
 
        dev_err(bus->parent, "Timeout: SMI busy for too long\n");
@@ -135,8 +118,6 @@ static int orion_mdio_smi_is_done(struct orion_mdio_dev *dev)
 
 static const struct orion_mdio_ops orion_mdio_smi_ops = {
        .is_done = orion_mdio_smi_is_done,
-       .poll_interval_min = MVMDIO_SMI_POLL_INTERVAL_MIN,
-       .poll_interval_max = MVMDIO_SMI_POLL_INTERVAL_MAX,
 };
 
 static int orion_mdio_smi_read(struct mii_bus *bus, int mii_id,
@@ -194,8 +175,6 @@ static int orion_mdio_xsmi_is_done(struct orion_mdio_dev *dev)
 
 static const struct orion_mdio_ops orion_mdio_xsmi_ops = {
        .is_done = orion_mdio_xsmi_is_done,
-       .poll_interval_min = MVMDIO_XSMI_POLL_INTERVAL_MIN,
-       .poll_interval_max = MVMDIO_XSMI_POLL_INTERVAL_MAX,
 };
 
 static int orion_mdio_xsmi_read_c45(struct mii_bus *bus, int mii_id,