[OpenWrt-Devel] [PATCH 08/10] imx6: add i2c retries for Ventana /dev/i2c-0

[Pushpal Sidhu]

On Ventana boards the Gateworks System Controller is the only device on I2C1
(/dev/i2c-0) and it can NAK transfers if it is busy in an ADC loop. Because
this is a multi-function device with several slave addresses it is best to
add retries at the controller level instead of within each slave driver. This
adds a patch that adds 3 retries for i2c transactions only for Ventana boards
and only for I2C1

Signed-off-by: Tim Harvey <tharvey at gateworks.com>
Signed-off-by: Pushpal Sidhu <psidhu at gateworks.com>
---
 ...x-add-retries-for-NAK-s-on-ventana-boards.patch | 24 ++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 target/linux/imx6/patches-4.3/207-i2c-imx-add-retries-for-NAK-s-on-ventana-boards.patch

diff --git a/target/linux/imx6/patches-4.3/207-i2c-imx-add-retries-for-NAK-s-on-ventana-boards.patch b/target/linux/imx6/patches-4.3/207-i2c-imx-add-retries-for-NAK-s-on-ventana-boards.patch
new file mode 100644
index 0000000..bfb5707
--- /dev/null
+++ b/target/linux/imx6/patches-4.3/207-i2c-imx-add-retries-for-NAK-s-on-ventana-boards.patch
@@ -0,0 +1,24 @@
+Index: linux-4.3/drivers/i2c/busses/i2c-imx.c
+===================================================================
+--- linux-4.3.orig/drivers/i2c/busses/i2c-imx.c	2015-11-01 16:05:25.000000000 -0800
++++ linux-4.3/drivers/i2c/busses/i2c-imx.c	2015-12-18 10:39:44.971158318 -0800
+@@ -461,6 +461,8 @@
+ {
+ 	if (imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR) & I2SR_RXAK) {
+ 		dev_dbg(&i2c_imx->adapter.dev, "<%s> No ACK\n", __func__);
++		if (i2c_imx->adapter.retries)
++			return -EAGAIN;
+ 		return -EIO;  /* No ACK */
+ 	}
+ 
+@@ -1010,6 +1012,10 @@
+ 	i2c_imx->adapter.nr		= pdev->id;
+ 	i2c_imx->adapter.dev.of_node	= pdev->dev.of_node;
+ 	i2c_imx->base			= base;
++	if (of_machine_is_compatible("gw,ventana") && phy_addr == 0x021a0000) {
++		dev_info(&pdev->dev, "Adding retries for Ventana GSC\n");
++		i2c_imx->adapter.retries = 3;
++	}
+ 
+ 	/* Get I2C clock */
+ 	i2c_imx->clk = devm_clk_get(&pdev->dev, NULL);
-- 
2.6.4
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