[PATCH 0/3] P2040/P2041 i2c recovery erratum

[PATCH 0/3] P2040/P2041 i2c recovery erratum

[Chris Packham]

The P2040/P2041 has an erratum where the i2c recovery scheme
documented in the reference manual (and currently implemented
in the i2c-mpc.c driver) does not work. The errata document
provides an alternative that does work. This series implements
that alternative and uses a property in the devicetree to
decide when the alternative mechanism is needed.

Chris Packham (3):
  dt-bindings: i2c: mpc: Add fsl,i2c-erratum-a004447 flag
  powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P2041 i2c
    controllers
  i2c: mpc: implement erratum A-004447 workaround

 .../devicetree/bindings/i2c/i2c-mpc.yaml      |  7 ++
 arch/powerpc/boot/dts/fsl/p2041si-post.dtsi   | 16 ++++
 drivers/i2c/busses/i2c-mpc.c                  | 88 ++++++++++++++++++-
 3 files changed, 109 insertions(+), 2 deletions(-)

-- 
2.31.1

[PATCH 1/3] dt-bindings: i2c: mpc: Add fsl,i2c-erratum-a004447 flag

[Chris Packham]

Document the fsl,i2c-erratum-a004447 flag which indicates the presence
of an i2c erratum on some QorIQ SoCs.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
 Documentation/devicetree/bindings/i2c/i2c-mpc.yaml | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/i2c/i2c-mpc.yaml b/Documentation/devicetree/bindings/i2c/i2c-mpc.yaml
index 7b553d559c83..98c6fcf7bf26 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-mpc.yaml
+++ b/Documentation/devicetree/bindings/i2c/i2c-mpc.yaml
@@ -46,6 +46,13 @@ properties:
     description: |
       I2C bus timeout in microseconds
 
+  fsl,i2c-erratum-a004447:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description: |
+      Indicates the presence of QorIQ erratum A-004447, which
+      says that the standard i2c recovery scheme mechanism does
+      not work and an alternate implementation is needed.
+
 required:
   - compatible
   - reg
-- 
2.31.1

[PATCH 2/3] powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P2041 i2c controllers

[Chris Packham]

The i2c controllers on the P2040/P2041 have an erratum where the
documented scheme for i2c bus recovery will not work (A-004447). A
different mechanism is needed which is documented in the P2040 Chip
Errata Rev Q (latest available at the time of writing).

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
 arch/powerpc/boot/dts/fsl/p2041si-post.dtsi | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/powerpc/boot/dts/fsl/p2041si-post.dtsi b/arch/powerpc/boot/dts/fsl/p2041si-post.dtsi
index 872e4485dc3f..ddc018d42252 100644
--- a/arch/powerpc/boot/dts/fsl/p2041si-post.dtsi
+++ b/arch/powerpc/boot/dts/fsl/p2041si-post.dtsi
@@ -371,7 +371,23 @@ sdhc@114000 {
 	};
 
 /include/ "qoriq-i2c-0.dtsi"
+	i2c@118000 {
+		fsl,i2c-erratum-a004447;
+	};
+
+	i2c@118100 {
+		fsl,i2c-erratum-a004447;
+	};
+
 /include/ "qoriq-i2c-1.dtsi"
+	i2c@119000 {
+		fsl,i2c-erratum-a004447;
+	};
+
+	i2c@119100 {
+		fsl,i2c-erratum-a004447;
+	};
+
 /include/ "qoriq-duart-0.dtsi"
 /include/ "qoriq-duart-1.dtsi"
 /include/ "qoriq-gpio-0.dtsi"
-- 
2.31.1

[PATCH 3/3] i2c: mpc: implement erratum A-004447 workaround

[Chris Packham]

The P2040/P2041 has an erratum where the normal i2c recovery mechanism
does not work. Implement the alternative recovery mechanism documented
in the P2040 Chip Errata Rev Q.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
 drivers/i2c/busses/i2c-mpc.c | 88 +++++++++++++++++++++++++++++++++++-
 1 file changed, 86 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index 30d9e89a3db2..052e37718771 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -45,6 +45,7 @@
 #define CCR_MTX  0x10
 #define CCR_TXAK 0x08
 #define CCR_RSTA 0x04
+#define CCR_RSVD 0x02
 
 #define CSR_MCF  0x80
 #define CSR_MAAS 0x40
@@ -97,7 +98,7 @@ struct mpc_i2c {
 	u32 block;
 	int rc;
 	int expect_rxack;
-
+	bool has_errata_A004447;
 };
 
 struct mpc_i2c_divider {
@@ -136,6 +137,83 @@ static void mpc_i2c_fixup(struct mpc_i2c *i2c)
 	}
 }
 
+static int i2c_mpc_wait_sr(struct mpc_i2c *i2c, int mask)
+{
+	unsigned long timeout = jiffies + usecs_to_jiffies(100);
+	int ret = 0;
+
+	while ((readb(i2c->base + MPC_I2C_SR) & mask) == 0) {
+		if (time_after(jiffies, timeout)) {
+			ret = -ETIMEDOUT;
+			break;
+		}
+		cond_resched();
+	}
+
+	return ret;
+}
+
+/*
+ * Workaround for Erratum A004447. From the P2040CE Rev Q
+ *
+ * 1.  Set up the frequency divider and sampling rate.
+ * 2.  I2CCR - a0h
+ * 3.  Poll for I2CSR[MBB] to get set.
+ * 4.  If I2CSR[MAL] is set (an indication that SDA is stuck low), then go to
+ *     step 5. If MAL is not set, then go to step 13.
+ * 5.  I2CCR - 00h
+ * 6.  I2CCR - 22h
+ * 7.  I2CCR - a2h
+ * 8.  Poll for I2CSR[MBB] to get set.
+ * 9.  Issue read to I2CDR.
+ * 10. Poll for I2CSR[MIF] to be set.
+ * 11. I2CCR - 82h
+ * 12. Workaround complete. Skip the next steps.
+ * 13. Issue read to I2CDR.
+ * 14. Poll for I2CSR[MIF] to be set.
+ * 15. I2CCR - 80h
+ */
+static void mpc_i2c_fixup_A004447(struct mpc_i2c *i2c)
+{
+	int ret;
+	u32 val;
+
+	writeccr(i2c, CCR_MEN | CCR_MSTA);
+	ret = i2c_mpc_wait_sr(i2c, CSR_MBB);
+	if (ret) {
+		dev_err(i2c->dev, "timeout waiting for CSR_MBB\n");
+		return;
+	}
+
+	val = readb(i2c->base + MPC_I2C_SR);
+
+	if (val & CSR_MAL) {
+		writeccr(i2c, 0x00);
+		writeccr(i2c, CCR_MSTA | CCR_RSVD);
+		writeccr(i2c, CCR_MEN | CCR_MSTA | CCR_RSVD);
+		ret = i2c_mpc_wait_sr(i2c, CSR_MBB);
+		if (ret) {
+			dev_err(i2c->dev, "timeout waiting for CSR_MBB\n");
+			return;
+		}
+		val = readb(i2c->base + MPC_I2C_DR);
+		ret = i2c_mpc_wait_sr(i2c, CSR_MIF);
+		if (ret) {
+			dev_err(i2c->dev, "timeout waiting for CSR_MIF\n");
+			return;
+		}
+		writeccr(i2c, CCR_MEN | CCR_RSVD);
+	} else {
+		val = readb(i2c->base + MPC_I2C_DR);
+		ret = i2c_mpc_wait_sr(i2c, CSR_MIF);
+		if (ret) {
+			dev_err(i2c->dev, "timeout waiting for CSR_MIF\n");
+			return;
+		}
+		writeccr(i2c, CCR_MEN);
+	}
+}
+
 #if defined(CONFIG_PPC_MPC52xx) || defined(CONFIG_PPC_MPC512x)
 static const struct mpc_i2c_divider mpc_i2c_dividers_52xx[] = {
 	{20, 0x20}, {22, 0x21}, {24, 0x22}, {26, 0x23},
@@ -670,7 +748,10 @@ static int fsl_i2c_bus_recovery(struct i2c_adapter *adap)
 {
 	struct mpc_i2c *i2c = i2c_get_adapdata(adap);
 
-	mpc_i2c_fixup(i2c);
+	if (i2c->has_errata_A004447)
+		mpc_i2c_fixup_A004447(i2c);
+	else
+		mpc_i2c_fixup(i2c);
 
 	return 0;
 }
@@ -767,6 +848,9 @@ static int fsl_i2c_probe(struct platform_device *op)
 	}
 	dev_info(i2c->dev, "timeout %u us\n", mpc_ops.timeout * 1000000 / HZ);
 
+	if (of_property_read_bool(op->dev.of_node, "fsl,i2c-erratum-a004447"))
+		i2c->has_errata_A004447 = true;
+
 	i2c->adap = mpc_ops;
 	scnprintf(i2c->adap.name, sizeof(i2c->adap.name),
 		  "MPC adapter (%s)", of_node_full_name(op->dev.of_node));
-- 
2.31.1