[4.2.y-ckt stable] Patch "i2c: designware: fix IO timeout issue for AMD controller" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    i2c: designware: fix IO timeout issue for AMD controller

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From cee20efb98210238bffed7d9091accd8645d570e Mon Sep 17 00:00:00 2001
From: Xiangliang Yu <Xiangliang.Yu at amd.com>
Date: Fri, 11 Dec 2015 20:02:53 +0800
Subject: i2c: designware: fix IO timeout issue for AMD controller

commit 2d244c81481fa5142a2ba6656ab7a8e40c849c27 upstream.

Because of some hardware limitation, AMD I2C controller can't
trigger pending interrupt if interrupt status has been changed
after clearing interrupt status bits. Then, I2C will lost
interrupt and IO timeout.

According to hardware design, this patch implements a workaround
to disable i2c controller interrupt and re-enable i2c interrupt
before exiting ISR.

To reduce the performance impacts on other vendors, use unlikely
function to check flag in ISR.

Signed-off-by: Xiangliang Yu <Xiangliang.Yu at amd.com>
Acked-by: Jarkko Nikula <jarkko.nikula at linux.intel.com>
Signed-off-by: Wolfram Sang <wsa at the-dreams.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/i2c/busses/i2c-designware-core.c    | 6 ++++++
 drivers/i2c/busses/i2c-designware-core.h    | 1 +
 drivers/i2c/busses/i2c-designware-platdrv.c | 7 ++++++-
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 6f19a33..75b1ffd 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -811,6 +811,12 @@ irqreturn_t i2c_dw_isr(int this_irq, void *dev_id)
 tx_aborted:
 	if ((stat & (DW_IC_INTR_TX_ABRT | DW_IC_INTR_STOP_DET)) || dev->msg_err)
 		complete(&dev->cmd_complete);
+	else if (unlikely(dev->accessor_flags & ACCESS_INTR_MASK)) {
+		/* workaround to trigger pending interrupt */
+		stat = dw_readl(dev, DW_IC_INTR_MASK);
+		i2c_dw_disable_int(dev);
+		dw_writel(dev, stat, DW_IC_INTR_MASK);
+	}

 	return IRQ_HANDLED;
 }
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index 9630222..808ef6a 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -111,6 +111,7 @@ struct dw_i2c_dev {

 #define ACCESS_SWAP		0x00000001
 #define ACCESS_16BIT		0x00000002
+#define ACCESS_INTR_MASK	0x00000004

 extern u32 dw_readl(struct dw_i2c_dev *dev, int offset);
 extern void dw_writel(struct dw_i2c_dev *dev, u32 b, int offset);
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 4bf5fc1..13a7f10 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -97,6 +97,7 @@ static void dw_i2c_acpi_params(struct platform_device *pdev, char method[],
 static int dw_i2c_acpi_configure(struct platform_device *pdev)
 {
 	struct dw_i2c_dev *dev = platform_get_drvdata(pdev);
+	const struct acpi_device_id *id;

 	dev->adapter.nr = -1;
 	dev->tx_fifo_depth = 32;
@@ -110,6 +111,10 @@ static int dw_i2c_acpi_configure(struct platform_device *pdev)
 	dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev->fs_lcnt,
 			   &dev->sda_hold_time);

+	id = acpi_match_device(pdev->dev.driver->acpi_match_table, &pdev->dev);
+	if (id && id->driver_data)
+		dev->accessor_flags |= (u32)id->driver_data;
+
 	return 0;
 }

@@ -120,7 +125,7 @@ static const struct acpi_device_id dw_i2c_acpi_match[] = {
 	{ "INT3433", 0 },
 	{ "80860F41", 0 },
 	{ "808622C1", 0 },
-	{ "AMD0010", 0 },
+	{ "AMD0010", ACCESS_INTR_MASK },
 	{ }
 };
 MODULE_DEVICE_TABLE(acpi, dw_i2c_acpi_match);
--
1.9.1