[U-Boot] [PATCH v4 1/2] i2c: mvtwsi: disable i2c slave on Armada 38x

[Baruch Siach]

Equivalent code that disables the hidden i2c0 slave already exists in
the Turris Omnia platform specific code. But this hidden i2c0 slave that
interferes the i2c bus is not board specific. Armada 38x SoCs and at
least some Kirkwood variants are affected as well. Add code to disable
this slave to the i2c bus driver to make it work on all affected
hardware.

Use the bind callback because we want this to always run at boot,
regardless of whether U-Boot uses the i2c bus.

Cc: Rabeeh Khoury <rabeeh at solid-run.com>
Cc: Chris Packham <judge.packham at gmail.com>
Reviewed-by: Stefan Roese <sr at denx.de>
Reviewed-by: Heiko Schocher <hs at denx.de>
Signed-off-by: Baruch Siach <baruch at tkos.co.il>
---
v4:
  * Add dummy 'debug' field to sunxi instead of platform #ifdef around
    the 'debug' field access (Stefan Roese, Heiko Schocher)

v3:
  * Fix build for SUNXI (Heiko Schocher)

v2:
  * Use clrbits_le32 (Stefan Roese)

  * Apply to Kirkwood (Chris Packham)

  * Add review tags from Stefan and Heiko
---
 drivers/i2c/mvtwsi.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/mvtwsi.c b/drivers/i2c/mvtwsi.c
index f9822e56b894..74ac0a4aa789 100644
--- a/drivers/i2c/mvtwsi.c
+++ b/drivers/i2c/mvtwsi.c
@@ -11,6 +11,7 @@
 #include <i2c.h>
 #include <linux/errno.h>
 #include <asm/io.h>
+#include <linux/bitops.h>
 #include <linux/compat.h>
 #ifdef CONFIG_DM_I2C
 #include <dm.h>
@@ -57,6 +58,7 @@ struct  mvtwsi_registers {
 	u32 status;
 	u32 baudrate;
 	u32 soft_reset;
+	u32 debug; /* Dummy field for build compatibility with mvebu */
 };
 
 #else
@@ -70,8 +72,10 @@ struct  mvtwsi_registers {
 		u32 baudrate;	/* When writing */
 	};
 	u32 xtnd_slave_addr;
-	u32 reserved[2];
+	u32 reserved0[2];
 	u32 soft_reset;
+	u32 reserved1[27];
+	u32 debug;
 };
 
 #endif
@@ -795,6 +799,23 @@ static int mvtwsi_i2c_ofdata_to_platdata(struct udevice *bus)
 	return 0;
 }
 
+static void twsi_disable_i2c_slave(struct mvtwsi_registers *twsi)
+{
+	clrbits_le32(&twsi->debug, BIT(18));
+}
+
+static int mvtwsi_i2c_bind(struct udevice *bus)
+{
+	struct mvtwsi_registers *twsi = devfdt_get_addr_ptr(bus);
+
+	/* Disable the hidden slave in i2c0 of these platforms */
+	if ((IS_ENABLED(CONFIG_ARMADA_38X) || IS_ENABLED(CONFIG_KIRKWOOD))
+			&& bus->req_seq == 0)
+		twsi_disable_i2c_slave(twsi);
+
+	return 0;
+}
+
 static int mvtwsi_i2c_probe(struct udevice *bus)
 {
 	struct mvtwsi_i2c_dev *dev = dev_get_priv(bus);
@@ -850,6 +871,7 @@ U_BOOT_DRIVER(i2c_mvtwsi) = {
 	.name = "i2c_mvtwsi",
 	.id = UCLASS_I2C,
 	.of_match = mvtwsi_i2c_ids,
+	.bind = mvtwsi_i2c_bind,
 	.probe = mvtwsi_i2c_probe,
 	.ofdata_to_platdata = mvtwsi_i2c_ofdata_to_platdata,
 	.priv_auto_alloc_size = sizeof(struct mvtwsi_i2c_dev),
-- 
2.17.1