Commit 7dd12fe3 authored by Tobias Waldekranz's avatar Tobias Waldekranz Committed by Jakub Kicinski
Browse files

net: mvmdio: Avoid excessive sleeps in polled mode 



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: default avatarTobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: default avatarAndrew Lunn <andrew@lunn.ch>
Tested-by: default avatarAndrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20231204100811.2708884-3-tobias@waldekranz.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent f3c92800

drivers/net/ethernet/marvell/mvmdio.c

+16 −37
Original line number Diff line number Diff line
@@ -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;



	while (1) {

	        if (ops->is_done(dev))

			return 0;

	        else if (timedout)

			break;

	unsigned long timeout;

	int done;



	if (dev->err_interrupt <= 0) {

			usleep_range(ops->poll_interval_min,

				     ops->poll_interval_max);



			if (time_is_before_jiffies(end))

				++timedout;

		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.

		 */

			if (timeout < 2)

				timeout = 2;

			wait_event_timeout(dev->smi_busy_wait,

				           ops->is_done(dev), timeout);

		timeout = max(usecs_to_jiffies(MVMDIO_SMI_TIMEOUT), 2);



			++timedout;

	        }

		if (wait_event_timeout(dev->smi_busy_wait,

				       ops->is_done(dev), timeout))

			return 0;

	}



	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,