[PATCH net-next v6 01/16] net: dsa: vsc73xx: use read_poll_timeout instead delay loop

Pawel Dembicki
2024-03-01T22:17:32Z

Switch the delay loop during the Arbiter empty check from
vsc73xx_adjust_link() to use read_poll_timeout(). Functionally,
one msleep() call is eliminated at the end of the loop in the timeout
case.

As Russell King suggested:

"This [change] avoids the issue that on the last iteration, the code reads
the register, tests it, finds the condition that's being waiting for is
false, _then_ waits and end up printing the error message - that last
wait is rather useless, and as the arbiter state isn't checked after
waiting, it could be that we had success during the last wait."

Suggested-by: Russell King <linux@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
---
v6:
- resend only
v5:
- improved commit description
- added two defines instead magic numbers
- added include with iopoll.h
v4:
- resend patch
v3:
- added "Reviewed-by" to commit message only
v2:
- introduced patch

drivers/net/dsa/vitesse-vsc73xx-core.c | 30 ++++++++++++++------------
1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
index ae70eac3be28..ab5771d4d828 100644
--- a/drivers/net/dsa/vitesse-vsc73xx-core.c
+++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
@@ -17,6 +17,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
+#include <linux/iopoll.h>
#include <linux/of.h>
#include <linux/of_mdio.h>
#include <linux/bitops.h>
@@ -268,6 +269,9 @@
#define IS_7398(a) ((a)->chipid == VSC73XX_CHIPID_ID_7398)
#define IS_739X(a) (IS_7395(a) || IS_7398(a))

+#define VSC73XX_POLL_SLEEP_US 1000
+#define VSC73XX_POLL_TIMEOUT_US 10000
+
struct vsc73xx_counter {
u8 counter;
const char *name;
@@ -779,7 +783,7 @@ static void vsc73xx_adjust_link(struct dsa_switch *ds, int port,
* after a PHY or the CPU port comes up or down.
*/
if (!phydev->link) {
- int maxloop = 10;
+ int ret, err;

dev_dbg(vsc->dev, "port %d: went down\n",
port);
@@ -794,19 +798,17 @@ static void vsc73xx_adjust_link(struct dsa_switch *ds, int port,
VSC73XX_ARBDISC, BIT(port), BIT(port));

/* Wait until queue is empty */
- vsc73xx_read(vsc, VSC73XX_BLOCK_ARBITER, 0,
- VSC73XX_ARBEMPTY, &val);
- while (!(val & BIT(port))) {
- msleep(1);
- vsc73xx_read(vsc, VSC73XX_BLOCK_ARBITER, 0,
- VSC73XX_ARBEMPTY, &val);
- if (--maxloop == 0) {
- dev_err(vsc->dev,
- "timeout waiting for block arbiter\n");
- /* Continue anyway */
- break;
- }
- }
+ ret = read_poll_timeout(vsc73xx_read, err,
+ err < 0 || (val & BIT(port)),
+ VSC73XX_POLL_SLEEP_US,
+ VSC73XX_POLL_TIMEOUT_US, false,
+ vsc, VSC73XX_BLOCK_ARBITER, 0,
+ VSC73XX_ARBEMPTY, &val);
+ if (ret)
+ dev_err(vsc->dev,
+ "timeout waiting for block arbiter\n");
+ else if (err < 0)
+ dev_err(vsc->dev, "error reading arbiter\n");

/* Put this port into reset */
vsc73xx_write(vsc, VSC73XX_BLOCK_MAC, port, VSC73XX_MAC_CFG,
--
2.34.1