[PATCH v4] i2c: mt7621: rework cmd/wait OPs to support atomic afer variant

[Christian Marangi <ansuelsmth@gmail.com>]

It was reported the need for atomic operation on some Airoha SoC that
makes use of I2C bus. Rework the cmd/wait OPs to suppor the xfer_atomic
variant. To support this it's needed to do the readl poll in
atomic context and special handling for device_reset.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---

Changes v4:
- Split to dedicated patch
- Reduce timeout to 250ms
- Disable device_reset in atomic context

Changes v3..v2:
- No related changes

 drivers/i2c/busses/i2c-mt7621.c | 75 ++++++++++++++++++++++-----------
 1 file changed, 51 insertions(+), 24 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mt7621.c b/drivers/i2c/busses/i2c-mt7621.c
index 9ea5e3f9a763..0283191ac518 100644
--- a/drivers/i2c/busses/i2c-mt7621.c
+++ b/drivers/i2c/busses/i2c-mt7621.c
@@ -67,27 +67,38 @@ struct mtk_i2c {
 	struct clk *clk;
 };
 
-static int mtk_i2c_wait_idle(struct mtk_i2c *i2c)
+static int mtk_i2c_wait_idle(struct mtk_i2c *i2c, bool atomic)
 {
 	int ret;
 	u32 val;
 
-	ret = readl_relaxed_poll_timeout(i2c->base + REG_SM0CTL1_REG,
-					 val, !(val & SM0CTL1_TRI),
-					 10, TIMEOUT_MS * 1000);
+	if (atomic)
+		ret = readl_relaxed_poll_timeout_atomic(i2c->base + REG_SM0CTL1_REG,
+							val, !(val & SM0CTL1_TRI),
+							10, TIMEOUT_MS * 250);
+	else
+		ret = readl_relaxed_poll_timeout(i2c->base + REG_SM0CTL1_REG,
+						 val, !(val & SM0CTL1_TRI),
+						 10, TIMEOUT_MS * 1000);
 	if (ret)
 		dev_dbg(i2c->dev, "idle err(%d)\n", ret);
 
 	return ret;
 }
 
-static void mtk_i2c_reset(struct mtk_i2c *i2c)
+static void mtk_i2c_reset(struct mtk_i2c *i2c, bool atomic)
 {
 	int ret;
 
-	ret = device_reset(i2c->adap.dev.parent);
-	if (ret)
-		dev_err(i2c->dev, "I2C reset failed!\n");
+	/*
+	 * Skip device_reset in atomic context as it depends on the
+	 * reset-controller correctly handling atomic operations.
+	 */
+	if (!atomic) {
+		ret = device_reset(i2c->adap.dev.parent);
+		if (ret)
+			dev_err(i2c->dev, "I2C reset failed!\n");
+	}
 
 	/*
 	 * Don't set SM0CTL0_ODRAIN as its bit meaning is inverted. To
@@ -117,27 +128,28 @@ static int mtk_i2c_check_ack(struct mtk_i2c *i2c, u32 expected)
 	return ((ack & ack_expected) == ack_expected) ? 0 : -ENXIO;
 }
 
-static int mtk_i2c_start(struct mtk_i2c *i2c)
+static int mtk_i2c_start(struct mtk_i2c *i2c, bool atomic)
 {
 	iowrite32(SM0CTL1_START | SM0CTL1_TRI, i2c->base + REG_SM0CTL1_REG);
-	return mtk_i2c_wait_idle(i2c);
+	return mtk_i2c_wait_idle(i2c, atomic);
 }
 
-static int mtk_i2c_stop(struct mtk_i2c *i2c)
+static int mtk_i2c_stop(struct mtk_i2c *i2c, bool atomic)
 {
 	iowrite32(SM0CTL1_STOP | SM0CTL1_TRI, i2c->base + REG_SM0CTL1_REG);
-	return mtk_i2c_wait_idle(i2c);
+	return mtk_i2c_wait_idle(i2c, atomic);
 }
 
-static int mtk_i2c_cmd(struct mtk_i2c *i2c, u32 cmd, int page_len)
+static int mtk_i2c_cmd(struct mtk_i2c *i2c, u32 cmd, int page_len,
+		       bool atomic)
 {
 	iowrite32(cmd | SM0CTL1_TRI | SM0CTL1_PGLEN(page_len),
 		  i2c->base + REG_SM0CTL1_REG);
-	return mtk_i2c_wait_idle(i2c);
+	return mtk_i2c_wait_idle(i2c, atomic);
 }
 
-static int mtk_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
-			int num)
+static int mtk_i2c_xfer_common(struct i2c_adapter *adap, struct i2c_msg *msgs,
+			       int num, bool atomic)
 {
 	struct mtk_i2c *i2c;
 	struct i2c_msg *pmsg;
@@ -151,12 +163,12 @@ static int mtk_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 		pmsg = &msgs[i];
 
 		/* wait hardware idle */
-		ret = mtk_i2c_wait_idle(i2c);
+		ret = mtk_i2c_wait_idle(i2c, atomic);
 		if (ret)
 			goto err_timeout;
 
 		/* start sequence */
-		ret = mtk_i2c_start(i2c);
+		ret = mtk_i2c_start(i2c, atomic);
 		if (ret)
 			goto err_timeout;
 
@@ -172,7 +184,8 @@ static int mtk_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 			len = 1;
 		}
 		iowrite32(addr, i2c->base + REG_SM0D0_REG);
-		ret = mtk_i2c_cmd(i2c, SM0CTL1_WRITE, len);
+		ret = mtk_i2c_cmd(i2c, SM0CTL1_WRITE, len,
+				  atomic);
 		if (ret)
 			goto err_timeout;
 
@@ -200,7 +213,7 @@ static int mtk_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 				cmd = SM0CTL1_WRITE;
 			}
 
-			ret = mtk_i2c_cmd(i2c, cmd, page_len);
+			ret = mtk_i2c_cmd(i2c, cmd, page_len, atomic);
 			if (ret)
 				goto err_timeout;
 
@@ -221,7 +234,7 @@ static int mtk_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 		}
 	}
 
-	ret = mtk_i2c_stop(i2c);
+	ret = mtk_i2c_stop(i2c, atomic);
 	if (ret)
 		goto err_timeout;
 
@@ -229,17 +242,30 @@ static int mtk_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 	return i;
 
 err_ack:
-	ret = mtk_i2c_stop(i2c);
+	ret = mtk_i2c_stop(i2c, atomic);
 	if (ret)
 		goto err_timeout;
 	return -ENXIO;
 
 err_timeout:
 	mtk_i2c_dump_reg(i2c);
-	mtk_i2c_reset(i2c);
+	mtk_i2c_reset(i2c, atomic);
+
 	return ret;
 }
 
+static int mtk_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+			int num)
+{
+	return mtk_i2c_xfer_common(adap, msgs, num, false);
+}
+
+static int mtk_i2c_xfer_atomic(struct i2c_adapter *adap,
+			       struct i2c_msg *msgs, int num)
+{
+	return mtk_i2c_xfer_common(adap, msgs, num, true);
+}
+
 static u32 mtk_i2c_func(struct i2c_adapter *a)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_PROTOCOL_MANGLING;
@@ -247,6 +273,7 @@ static u32 mtk_i2c_func(struct i2c_adapter *a)
 
 static const struct i2c_algorithm mtk_i2c_algo = {
 	.xfer = mtk_i2c_xfer,
+	.xfer_atomic = mtk_i2c_xfer_atomic,
 	.functionality = mtk_i2c_func,
 };
 
@@ -265,7 +292,7 @@ static void mtk_i2c_init(struct mtk_i2c *i2c)
 	if (i2c->clk_div > SM0CTL0_CLK_DIV_MAX)
 		i2c->clk_div = SM0CTL0_CLK_DIV_MAX;
 
-	mtk_i2c_reset(i2c);
+	mtk_i2c_reset(i2c, false);
 }
 
 static int mtk_i2c_probe(struct platform_device *pdev)
-- 
2.55.0