[net-next RFC PATCH v3 15/15] net: dsa: qca8k: cache lo and hi for mdio write

[Ansuel Smith <ansuelsmth@gmail.com>]

From Documentation, we can cache lo and hi the same way we do with the
page. This massively reduce the mdio write as 3/4 of the time we only
require to write the lo or hi part for a mdio write.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 drivers/net/dsa/qca8k.c | 49 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 44 insertions(+), 5 deletions(-)

diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
index 375a1d34e46f..b109a74031c6 100644
--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c
@@ -94,6 +94,48 @@ qca8k_split_addr(u32 regaddr, u16 *r1, u16 *r2, u16 *page)
 	*page = regaddr & 0x3ff;
 }
 
+static u16 qca8k_current_lo = 0xffff;
+
+static int
+qca8k_set_lo(struct mii_bus *bus, int phy_id, u32 regnum, u16 lo)
+{
+	int ret;
+
+	if (lo == qca8k_current_lo) {
+		// pr_info("SAME LOW");
+		return 0;
+	}
+
+	ret = bus->write(bus, phy_id, regnum, lo);
+	if (ret < 0)
+		dev_err_ratelimited(&bus->dev,
+				    "failed to write qca8k 32bit lo register\n");
+
+	qca8k_current_lo = lo;
+	return 0;
+}
+
+static u16 qca8k_current_hi = 0xffff;
+
+static int
+qca8k_set_hi(struct mii_bus *bus, int phy_id, u32 regnum, u16 hi)
+{
+	int ret;
+
+	if (hi == qca8k_current_hi) {
+		// pr_info("SAME HI");
+		return 0;
+	}
+
+	ret = bus->write(bus, phy_id, regnum, hi);
+	if (ret < 0)
+		dev_err_ratelimited(&bus->dev,
+				    "failed to write qca8k 32bit hi register\n");
+
+	qca8k_current_hi = hi;
+	return 0;
+}
+
 static int
 qca8k_mii_read32(struct mii_bus *bus, int phy_id, u32 regnum, u32 *val)
 {
@@ -125,12 +167,9 @@ qca8k_mii_write32(struct mii_bus *bus, int phy_id, u32 regnum, u32 val)
 	lo = val & 0xffff;
 	hi = (u16)(val >> 16);
 
-	ret = bus->write(bus, phy_id, regnum, lo);
+	ret = qca8k_set_lo(bus, phy_id, regnum, lo);
 	if (ret >= 0)
-		ret = bus->write(bus, phy_id, regnum + 1, hi);
-	if (ret < 0)
-		dev_err_ratelimited(&bus->dev,
-				    "failed to write qca8k 32bit register\n");
+		ret = qca8k_set_hi(bus, phy_id, regnum + 1, hi);
 }
 
 static int
-- 
2.32.0