[PATCH net-next 3/4] net: phy: mscc-miim: improve waiting logic

[Antoine Tenart]

The MSCC MIIM MDIO driver uses a waiting logic to wait for the MDIO bus
to be ready to accept next commands. It does so by polling the BUSY
status bit which indicates the MDIO bus has completed all pending
operations. This can take time, and the controller supports writing the
next command as soon as there are no pending commands (which happens
while the MDIO bus is busy completing its current command).

This patch implements this improved logic by adding an helper to poll
the PENDING status bit, and by adjusting where we should wait for the
bus to not be busy or to not be pending.

Signed-off-by: Antoine Tenart <antoine.ten...@bootlin.com>
---
 drivers/net/phy/mdio-mscc-miim.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/mdio-mscc-miim.c b/drivers/net/phy/mdio-mscc-miim.c
index 42119f661452..aed9afa1e8f1 100644
--- a/drivers/net/phy/mdio-mscc-miim.c
+++ b/drivers/net/phy/mdio-mscc-miim.c
@@ -16,6 +16,7 @@
 #include <linux/of_mdio.h>
 
 #define MSCC_MIIM_REG_STATUS           0x0
+#define                MSCC_MIIM_STATUS_STAT_PENDING   BIT(2)
 #define                MSCC_MIIM_STATUS_STAT_BUSY      BIT(3)
 #define MSCC_MIIM_REG_CMD              0x8
 #define                MSCC_MIIM_CMD_OPR_WRITE         BIT(1)
@@ -47,13 +48,23 @@ static int mscc_miim_wait_ready(struct mii_bus *bus)
                                  !(val & MSCC_MIIM_STATUS_STAT_BUSY), 50, 
10000);
 }
 
+static int mscc_miim_wait_pending(struct mii_bus *bus)
+{
+       struct mscc_miim_dev *miim = bus->priv;
+       u32 val;
+
+       return readl_poll_timeout(miim->regs + MSCC_MIIM_REG_STATUS, val,
+                                 !(val & MSCC_MIIM_STATUS_STAT_PENDING),
+                                 50, 10000);
+}
+
 static int mscc_miim_read(struct mii_bus *bus, int mii_id, int regnum)
 {
        struct mscc_miim_dev *miim = bus->priv;
        u32 val;
        int ret;
 
-       ret = mscc_miim_wait_ready(bus);
+       ret = mscc_miim_wait_pending(bus);
        if (ret)
                goto out;
 
@@ -82,7 +93,7 @@ static int mscc_miim_write(struct mii_bus *bus, int mii_id,
        struct mscc_miim_dev *miim = bus->priv;
        int ret;
 
-       ret = mscc_miim_wait_ready(bus);
+       ret = mscc_miim_wait_pending(bus);
        if (ret < 0)
                goto out;
 
-- 
2.26.2