[PATCH 6.6 101/322] net: mvmdio: Avoid excessive sleeps in polled mode

Greg Kroah-Hartman
2024-02-03T04:12:52Z

From: Tobias Waldekranz <tobias@waldekranz.com>

[ 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>
---
drivers/net/ethernet/marvell/mvmdio.c | 53 ++++++++-------------------
1 file changed, 16 insertions(+), 37 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvmdio.c b/drivers/net/ethernet/marvell/mvmdio.c
index 674913184ebf..2ef613a237d8 100644
--- 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,
--
2.43.0