Merge branch 'dsa-qca8k-fixes'

Christian Marangi says:

====================
net: dsa: qca8k: multiple fix on mdio read/write

Due to some problems in reading the Documentation and elaborating it
some wrong assumption were done. The error was reported and notice only
now due to how things are setup in the code flow.

First 2 patch fix mgmt eth where the lenght calculation is very
confusing and in step of word size. (the related commit description have
an extensive description about how this mess works)

Last 3 patch revert the broken mdio cache and apply a correct version
that should still save some extra mdio in phy poll secnario.

These 5 patch fix each related problem and apply what the Documentation
actually say.

Changes v2:
- Add cover letter
- Fix typo in revert patch
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 109 insertions, 64 deletions

diff --git a/drivers/net/dsa/qca/qca8k-8xxx.c b/drivers/net/dsa/qca/qca8k-8xxx.c
index c5c3b4e92f28bf..2f224b166bbb32 100644
--- a/drivers/net/dsa/qca/qca8k-8xxx.c
+++ b/drivers/net/dsa/qca/qca8k-8xxx.c
@@ -37,77 +37,104 @@ qca8k_split_addr(u32 regaddr, u16 *r1, u16 *r2, u16 *page)
 }
 
 static int
-qca8k_set_lo(struct qca8k_priv *priv, int phy_id, u32 regnum, u16 lo)
+qca8k_mii_write_lo(struct mii_bus *bus, int phy_id, u32 regnum, u32 val)
 {
-	u16 *cached_lo = &priv->mdio_cache.lo;
-	struct mii_bus *bus = priv->bus;
 	int ret;
+	u16 lo;
 
-	if (lo == *cached_lo)
-		return 0;
-
+	lo = val & 0xffff;
 	ret = bus->write(bus, phy_id, regnum, lo);
 	if (ret < 0)
 		dev_err_ratelimited(&bus->dev,
 				    "failed to write qca8k 32bit lo register\n");
 
-	*cached_lo = lo;
-	return 0;
+	return ret;
 }
 
 static int
-qca8k_set_hi(struct qca8k_priv *priv, int phy_id, u32 regnum, u16 hi)
+qca8k_mii_write_hi(struct mii_bus *bus, int phy_id, u32 regnum, u32 val)
 {
-	u16 *cached_hi = &priv->mdio_cache.hi;
-	struct mii_bus *bus = priv->bus;
 	int ret;
+	u16 hi;
 
-	if (hi == *cached_hi)
-		return 0;
-
+	hi = (u16)(val >> 16);
 	ret = bus->write(bus, phy_id, regnum, hi);
 	if (ret < 0)
 		dev_err_ratelimited(&bus->dev,
 				    "failed to write qca8k 32bit hi register\n");
 
-	*cached_hi = hi;
-	return 0;
+	return ret;
 }
 
 static int
-qca8k_mii_read32(struct mii_bus *bus, int phy_id, u32 regnum, u32 *val)
+qca8k_mii_read_lo(struct mii_bus *bus, int phy_id, u32 regnum, u32 *val)
 {
 	int ret;
 
 	ret = bus->read(bus, phy_id, regnum);
-	if (ret >= 0) {
-		*val = ret;
-		ret = bus->read(bus, phy_id, regnum + 1);
-		*val |= ret << 16;
-	}
+	if (ret < 0)
+		goto err;
 
-	if (ret < 0) {
-		dev_err_ratelimited(&bus->dev,
-				    "failed to read qca8k 32bit register\n");
-		*val = 0;
-		return ret;
-	}
+	*val = ret & 0xffff;
+	return 0;
+
+err:
+	dev_err_ratelimited(&bus->dev,
+			    "failed to read qca8k 32bit lo register\n");
+	*val = 0;
+
+	return ret;
+}
 
+static int
+qca8k_mii_read_hi(struct mii_bus *bus, int phy_id, u32 regnum, u32 *val)
+{
+	int ret;
+
+	ret = bus->read(bus, phy_id, regnum);
+	if (ret < 0)
+		goto err;
+
+	*val = ret << 16;
 	return 0;
+
+err:
+	dev_err_ratelimited(&bus->dev,
+			    "failed to read qca8k 32bit hi register\n");
+	*val = 0;
+
+	return ret;
 }
 
-static void
-qca8k_mii_write32(struct qca8k_priv *priv, int phy_id, u32 regnum, u32 val)
+static int
+qca8k_mii_read32(struct mii_bus *bus, int phy_id, u32 regnum, u32 *val)
 {
-	u16 lo, hi;
+	u32 hi, lo;
 	int ret;
 
-	lo = val & 0xffff;
-	hi = (u16)(val >> 16);
+	*val = 0;
 
-	ret = qca8k_set_lo(priv, phy_id, regnum, lo);
-	if (ret >= 0)
-		ret = qca8k_set_hi(priv, phy_id, regnum + 1, hi);
+	ret = qca8k_mii_read_lo(bus, phy_id, regnum, &lo);
+	if (ret < 0)
+		goto err;
+
+	ret = qca8k_mii_read_hi(bus, phy_id, regnum + 1, &hi);
+	if (ret < 0)
+		goto err;
+
+	*val = lo | hi;
+
+err:
+	return ret;
+}
+
+static void
+qca8k_mii_write32(struct mii_bus *bus, int phy_id, u32 regnum, u32 val)
+{
+	if (qca8k_mii_write_lo(bus, phy_id, regnum, val) < 0)
+		return;
+
+	qca8k_mii_write_hi(bus, phy_id, regnum + 1, val);
 }
 
 static int
@@ -146,7 +173,16 @@ static void qca8k_rw_reg_ack_handler(struct dsa_switch *ds, struct sk_buff *skb)
 
 	command = get_unaligned_le32(&mgmt_ethhdr->command);
 	cmd = FIELD_GET(QCA_HDR_MGMT_CMD, command);
+
 	len = FIELD_GET(QCA_HDR_MGMT_LENGTH, command);
+	/* Special case for len of 15 as this is the max value for len and needs to
+	 * be increased before converting it from word to dword.
+	 */
+	if (len == 15)
+		len++;
+
+	/* We can ignore odd value, we always round up them in the alloc function. */
+	len *= sizeof(u16);
 
 	/* Make sure the seq match the requested packet */
 	if (get_unaligned_le32(&mgmt_ethhdr->seq) == mgmt_eth_data->seq)
@@ -193,17 +229,33 @@ static struct sk_buff *qca8k_alloc_mdio_header(enum mdio_cmd cmd, u32 reg, u32 *
 	if (!skb)
 		return NULL;
 
-	/* Max value for len reg is 15 (0xf) but the switch actually return 16 byte
-	 * Actually for some reason the steps are:
-	 * 0: nothing
-	 * 1-4: first 4 byte
-	 * 5-6: first 12 byte
-	 * 7-15: all 16 byte
+	/* Hdr mgmt length value is in step of word size.
+	 * As an example to process 4 byte of data the correct length to set is 2.
+	 * To process 8 byte 4, 12 byte 6, 16 byte 8...
+	 *
+	 * Odd values will always return the next size on the ack packet.
+	 * (length of 3 (6 byte) will always return 8 bytes of data)
+	 *
+	 * This means that a value of 15 (0xf) actually means reading/writing 32 bytes
+	 * of data.
+	 *
+	 * To correctly calculate the length we devide the requested len by word and
+	 * round up.
+	 * On the ack function we can skip the odd check as we already handle the
+	 * case here.
 	 */
-	if (len == 16)
-		real_len = 15;
-	else
-		real_len = len;
+	real_len = DIV_ROUND_UP(len, sizeof(u16));
+
+	/* We check if the result len is odd and we round up another time to
+	 * the next size. (length of 3 will be increased to 4 as switch will always
+	 * return 8 bytes)
+	 */
+	if (real_len % sizeof(u16) != 0)
+		real_len++;
+
+	/* Max reg value is 0xf(15) but switch will always return the next size (32 byte) */
+	if (real_len == 16)
+		real_len--;
 
 	skb_reset_mac_header(skb);
 	skb_set_network_header(skb, skb->len);
@@ -417,7 +469,7 @@ qca8k_regmap_write(void *ctx, uint32_t reg, uint32_t val)
 	if (ret < 0)
 		goto exit;
 
-	qca8k_mii_write32(priv, 0x10 | r2, r1, val);
+	qca8k_mii_write32(bus, 0x10 | r2, r1, val);
 
 exit:
 	mutex_unlock(&bus->mdio_lock);
@@ -450,7 +502,7 @@ qca8k_regmap_update_bits(void *ctx, uint32_t reg, uint32_t mask, uint32_t write_
 
 	val &= ~mask;
 	val |= write_val;
-	qca8k_mii_write32(priv, 0x10 | r2, r1, val);
+	qca8k_mii_write32(bus, 0x10 | r2, r1, val);
 
 exit:
 	mutex_unlock(&bus->mdio_lock);
@@ -688,9 +740,9 @@ qca8k_mdio_busy_wait(struct mii_bus *bus, u32 reg, u32 mask)
 
 	qca8k_split_addr(reg, &r1, &r2, &page);
 
-	ret = read_poll_timeout(qca8k_mii_read32, ret1, !(val & mask), 0,
+	ret = read_poll_timeout(qca8k_mii_read_hi, ret1, !(val & mask), 0,
 				QCA8K_BUSY_WAIT_TIMEOUT * USEC_PER_MSEC, false,
-				bus, 0x10 | r2, r1, &val);
+				bus, 0x10 | r2, r1 + 1, &val);
 
 	/* Check if qca8k_read has failed for a different reason
 	 * before returnting -ETIMEDOUT
@@ -725,14 +777,14 @@ qca8k_mdio_write(struct qca8k_priv *priv, int phy, int regnum, u16 data)
 	if (ret)
 		goto exit;
 
-	qca8k_mii_write32(priv, 0x10 | r2, r1, val);
+	qca8k_mii_write32(bus, 0x10 | r2, r1, val);
 
 	ret = qca8k_mdio_busy_wait(bus, QCA8K_MDIO_MASTER_CTRL,
 				   QCA8K_MDIO_MASTER_BUSY);
 
 exit:
 	/* even if the busy_wait timeouts try to clear the MASTER_EN */
-	qca8k_mii_write32(priv, 0x10 | r2, r1, 0);
+	qca8k_mii_write_hi(bus, 0x10 | r2, r1 + 1, 0);
 
 	mutex_unlock(&bus->mdio_lock);
 
@@ -762,18 +814,18 @@ qca8k_mdio_read(struct qca8k_priv *priv, int phy, int regnum)
 	if (ret)
 		goto exit;
 
-	qca8k_mii_write32(priv, 0x10 | r2, r1, val);
+	qca8k_mii_write_hi(bus, 0x10 | r2, r1 + 1, val);
 
 	ret = qca8k_mdio_busy_wait(bus, QCA8K_MDIO_MASTER_CTRL,
 				   QCA8K_MDIO_MASTER_BUSY);
 	if (ret)
 		goto exit;
 
-	ret = qca8k_mii_read32(bus, 0x10 | r2, r1, &val);
+	ret = qca8k_mii_read_lo(bus, 0x10 | r2, r1, &val);
 
 exit:
 	/* even if the busy_wait timeouts try to clear the MASTER_EN */
-	qca8k_mii_write32(priv, 0x10 | r2, r1, 0);
+	qca8k_mii_write_hi(bus, 0x10 | r2, r1 + 1, 0);
 
 	mutex_unlock(&bus->mdio_lock);
 
@@ -1943,8 +1995,6 @@ qca8k_sw_probe(struct mdio_device *mdiodev)
 	}
 
 	priv->mdio_cache.page = 0xffff;
-	priv->mdio_cache.lo = 0xffff;
-	priv->mdio_cache.hi = 0xffff;
 
 	/* Check the detected switch id */
 	ret = qca8k_read_switch_id(priv);
diff --git a/drivers/net/dsa/qca/qca8k.h b/drivers/net/dsa/qca/qca8k.h
index 0b7a5cb1232167..03514f7a20becc 100644
--- a/drivers/net/dsa/qca/qca8k.h
+++ b/drivers/net/dsa/qca/qca8k.h
@@ -375,11 +375,6 @@ struct qca8k_mdio_cache {
  * mdio writes
  */
 	u16 page;
-/* lo and hi can also be cached and from Documentation we can skip one
- * extra mdio write if lo or hi is didn't change.
- */
-	u16 lo;
-	u16 hi;
 };
 
 struct qca8k_pcs {
diff --git a/include/linux/dsa/tag_qca.h b/include/linux/dsa/tag_qca.h
index b1b5720d89a596..ee657452f122a8 100644
--- a/include/linux/dsa/tag_qca.h
+++ b/include/linux/dsa/tag_qca.h
@@ -45,8 +45,8 @@ struct sk_buff;
 					QCA_HDR_MGMT_COMMAND_LEN + \
 					QCA_HDR_MGMT_DATA1_LEN)
 
-#define QCA_HDR_MGMT_DATA2_LEN		12 /* Other 12 byte for the mdio data */
-#define QCA_HDR_MGMT_PADDING_LEN	34 /* Padding to reach the min Ethernet packet */
+#define QCA_HDR_MGMT_DATA2_LEN		28 /* Other 28 byte for the mdio data */
+#define QCA_HDR_MGMT_PADDING_LEN	18 /* Padding to reach the min Ethernet packet */
 
 #define QCA_HDR_MGMT_PKT_LEN		(QCA_HDR_MGMT_HEADER_LEN + \
 					QCA_HDR_LEN + \