[PATCH v4 0/3] Extend dt bindings to support I2C on sifive devices and a fix broken IRQ in polling mode.

[PATCH v4 0/3] Extend dt bindings to support I2C on sifive devices and a fix broken IRQ in polling mode.

[Sagar Shrikant Kadam]

The patch is based on mainline v5.1 and extends DT-bindings for Opencore based I2C IP block reimplemented 
in FU540 SoC, available on HiFive unleashed board (Rev A00), and also provides a workaround for broken IRQ
which affects the already available I2C polling mode interface in mainline, for FU540-C000 chipsets. 

The polling mode workaround patch fixes the CPU stall issue, when-ever i2c transfer are initiated.

This workaround checks if it's a FU540 chipset based on device tree information, and check's for open
core's IF(interrupt flag) and TIP flags to break from the polling loop upon completion of transfer.

To test the patch, a PMOD-AD2 sensor is connected to HiFive Unleashed board over J1 connector, and 
appropriate device node is added into board specific device tree as per the information provided in 
dt-bindings in Documentation/devicetree/bindings/i2c/i2c-sifive.txt.
Without this workaround, the CPU stall's infinitely.

Busybox i2c utilities used to verify workaround : i2cdetect, i2cdump, i2cset, i2cget


Patch History:

V3<->V4:
-Incorporated suggestions on v3 patch as follows:
-OCORES_FLAG_BROKEN_IRQ BIT position rectified.
-Updated BORKEN_IRQ flag checks such that if sifive device (Fu540-C000) is identified,then use polling mode as IRQ is broken.

V2<->V3:
-Incorporated review comments on v2 patch as follows:
-Rectified compatibility string sequence with the most specific one at the first (dt bindings). 
-Moved interrupts and interrupt-parent under optional property list (dt-bindings).
-Updated reference to sifive-blocks-ip-versioning.txt and URL to IP repository used (dt-bindings).
-Removed example for i2c0 device node from binding doc (dt-bindings).
-Included sifive,i2c0 device under compatibility table in i2c-ocores driver (i2c-ocores).
-Updated polling mode hooks for SoC specific fix to handle broken IRQ (i2c-ocores).


V1<->V2:
-Incorporate review comments from Andrew
-Extend dt bindings into i2c-ocores.txt instead of adding new file
-Rename SIFIVE_FLAG_POLL to OCORES_FLAG_BROKEN_IRQ

V1:
-Update dt bindings for sifive i2c devices
-Fix broken IRQ affecting i2c polling mode interface.

Sagar Shrikant Kadam (3):
  dt-bindings: i2c: extend existing opencore bindings.
  i2c-ocores: sifive: add support for i2c device on FU540-c000 SoC.
  i2c-ocores: sifive: add polling mode workaround for FU540-C000 SoC

 .../devicetree/bindings/i2c/i2c-ocores.txt         |  7 +++-
 drivers/i2c/busses/i2c-ocores.c                    | 40 +++++++++++++++++++---
 2 files changed, 41 insertions(+), 6 deletions(-)

-- 
1.9.1


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[PATCH v4 1/3] dt-bindings: i2c: extend existing opencore bindings.

[Sagar Shrikant Kadam]

Add FU540-C000 specific device tree bindings to already
available i2-ocores file. This device is available on
HiFive Unleashed Rev A00 board. Move interrupt and interrupt
parents under optional property list as these can be optional.

The FU540-C000 SoC from sifive, has an Opencore's I2C block
reimplementation.

The DT compatibility string for this IP is present in HDL and available at.
https://github.com/sifive/sifive-blocks/blob/master/src/main/scala/devices/i2c/I2C.scala#L73

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
 Documentation/devicetree/bindings/i2c/i2c-ocores.txt | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
index 17bef9a..b73960e 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
@@ -2,8 +2,11 @@ Device tree configuration for i2c-ocores
 
 Required properties:
 - compatible      : "opencores,i2c-ocores" or "aeroflexgaisler,i2cmst"
+                    "sifive,fu540-c000-i2c" or "sifive,i2c0".
+		    for Opencore based I2C IP block reimplemented in
+		    FU540-C000 SoC.Please refer sifive-blocks-ip-versioning.txt
+		    for additional details.
 - reg             : bus address start and address range size of device
-- interrupts      : interrupt number
 - clocks          : handle to the controller clock; see the note below.
                     Mutually exclusive with opencores,ip-clock-frequency
 - opencores,ip-clock-frequency: frequency of the controller clock in Hz;
@@ -12,6 +15,8 @@ Required properties:
 - #size-cells     : should be <0>
 
 Optional properties:
+- interrupt-parent: handle to interrupt controller.
+- interrupts      : interrupt number.
 - clock-frequency : frequency of bus clock in Hz; see the note below.
                     Defaults to 100 KHz when the property is not specified
 - reg-shift       : device register offsets are shifted by this value
-- 
1.9.1


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[PATCH v4 2/3] i2c-ocores: sifive: add support for i2c device on FU540-c000 SoC.

[Sagar Shrikant Kadam]

Update device id table for Opencore's I2C master based re-implementation
used in FU540-c000 chipset on HiFive Unleashed platform.

Device ID's include Sifive, soc-specific device for chip specific tweaks
and sifive IP block specific device for generic programming model.

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
 drivers/i2c/busses/i2c-ocores.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
index 4e1a077..aee1d86 100644
--- a/drivers/i2c/busses/i2c-ocores.c
+++ b/drivers/i2c/busses/i2c-ocores.c
@@ -85,6 +85,7 @@ struct ocores_i2c {
 
 #define TYPE_OCORES		0
 #define TYPE_GRLIB		1
+#define TYPE_SIFIVE_REV0	2
 
 static void oc_setreg_8(struct ocores_i2c *i2c, int reg, u8 value)
 {
@@ -468,6 +469,14 @@ static u32 ocores_func(struct i2c_adapter *adap)
 		.compatible = "aeroflexgaisler,i2cmst",
 		.data = (void *)TYPE_GRLIB,
 	},
+	{
+		.compatible = "sifive,fu540-c000-i2c",
+		.data = (void *)TYPE_SIFIVE_REV0,
+	},
+	{
+		.compatible = "sifive,i2c0",
+		.data = (void *)TYPE_SIFIVE_REV0,
+	},
 	{},
 };
 MODULE_DEVICE_TABLE(of, ocores_i2c_match);
-- 
1.9.1


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[PATCH v4 3/3] i2c-ocores: sifive: add polling mode workaround for FU540-C000 SoC

[Sagar Shrikant Kadam]

The i2c-ocore driver already has a polling mode interface.But it needs
a workaround for FU540 Chipset on HiFive unleashed board (RevA00).
There is an erratum in FU540 chip that prevents interrupt driven i2c
transfers from working, and also the I2C controller's interrupt bit
cannot be cleared if set, due to this the existing i2c polling mode
interface added in mainline earlier doesn't work, and CPU stall's
infinitely, when-ever i2c transfer is initiated.

Ref:previous polling mode support in mainline

	commit 69c8c0c0efa8 ("i2c: ocores: add polling interface")

The workaround / fix under OCORES_FLAG_BROKEN_IRQ is particularly for
FU540-COOO SoC.

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
 drivers/i2c/busses/i2c-ocores.c | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
index aee1d86..e0d7f24 100644
--- a/drivers/i2c/busses/i2c-ocores.c
+++ b/drivers/i2c/busses/i2c-ocores.c
@@ -27,6 +27,7 @@
 #include <linux/jiffies.h>
 
 #define OCORES_FLAG_POLL BIT(0)
+#define OCORES_FLAG_BROKEN_IRQ BIT(1) /* Broken IRQ for FU540-C000 SoC */
 
 /*
  * 'process_lock' exists because ocores_process() and ocores_process_timeout()
@@ -239,9 +240,13 @@ static irqreturn_t ocores_isr(int irq, void *dev_id)
 	struct ocores_i2c *i2c = dev_id;
 	u8 stat = oc_getreg(i2c, OCI2C_STATUS);
 
-	if (!(stat & OCI2C_STAT_IF))
+	if (i2c->flags & OCORES_FLAG_BROKEN_IRQ) {
+		if (stat & OCI2C_STAT_IF)
+			if (!(stat & OCI2C_STAT_BUSY))
+				return IRQ_NONE;
+	} else if (!(stat & OCI2C_STAT_IF)) {
 		return IRQ_NONE;
-
+	}
 	ocores_process(i2c, stat);
 
 	return IRQ_HANDLED;
@@ -356,6 +361,11 @@ static void ocores_process_polling(struct ocores_i2c *i2c)
 		ret = ocores_isr(-1, i2c);
 		if (ret == IRQ_NONE)
 			break; /* all messages have been transferred */
+		else {
+			if (i2c->flags & OCORES_FLAG_BROKEN_IRQ)
+				if (i2c->state == STATE_DONE)
+					break;
+		}
 	}
 }
 
@@ -406,7 +416,7 @@ static int ocores_xfer(struct i2c_adapter *adap,
 {
 	struct ocores_i2c *i2c = i2c_get_adapdata(adap);
 
-	if (i2c->flags & OCORES_FLAG_POLL)
+	if ((i2c->flags & (OCORES_FLAG_POLL | OCORES_FLAG_BROKEN_IRQ)))
 		return ocores_xfer_polling(adap, msgs, num);
 	return ocores_xfer_core(i2c, msgs, num, false);
 }
@@ -601,6 +611,7 @@ static int ocores_i2c_probe(struct platform_device *pdev)
 {
 	struct ocores_i2c *i2c;
 	struct ocores_i2c_platform_data *pdata;
+	const struct of_device_id *match;
 	struct resource *res;
 	int irq;
 	int ret;
@@ -682,13 +693,23 @@ static int ocores_i2c_probe(struct platform_device *pdev)
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq == -ENXIO) {
-		i2c->flags |= OCORES_FLAG_POLL;
+		/*
+		 * Set a OCORES_FLAG_BROKEN_IRQ to enable workaround for
+		 * FU540-C000 SoC in polling mode interface of i2c-ocore driver.
+		 * Else enable default polling mode interface for SIFIVE/OCORE
+		 * device types.
+		 */
+		match = of_match_node(ocores_i2c_match, pdev->dev.of_node);
+		if (match && (long)match->data == TYPE_SIFIVE_REV0)
+			i2c->flags |= OCORES_FLAG_BROKEN_IRQ;
+		else
+			i2c->flags |= OCORES_FLAG_POLL;
 	} else {
 		if (irq < 0)
 			return irq;
 	}
 
-	if (!(i2c->flags & OCORES_FLAG_POLL)) {
+	if (!(i2c->flags & (OCORES_FLAG_POLL | OCORES_FLAG_BROKEN_IRQ))) {
 		ret = devm_request_irq(&pdev->dev, irq, ocores_isr, 0,
 				       pdev->name, i2c);
 		if (ret) {
-- 
1.9.1


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Re: [PATCH v4 3/3] i2c-ocores: sifive: add polling mode workaround for FU540-C000 SoC

[Andrew Lunn]

> @@ -406,7 +416,7 @@ static int ocores_xfer(struct i2c_adapter *adap,
>  {
>  	struct ocores_i2c *i2c = i2c_get_adapdata(adap);
>  
> -	if (i2c->flags & OCORES_FLAG_POLL)
> +	if ((i2c->flags & (OCORES_FLAG_POLL | OCORES_FLAG_BROKEN_IRQ)))
>  		return ocores_xfer_polling(adap, msgs, num);
>  	return ocores_xfer_core(i2c, msgs, num, false);
>  }

You are not listening to what i said. All you need to know here is
that you must poll. It does not matter if the IRQ is broken or not.

>  	irq = platform_get_irq(pdev, 0);
>  	if (irq == -ENXIO) {
> -		i2c->flags |= OCORES_FLAG_POLL;

If there is no interrupt, you need to poll. So keep this line.

> +		/*
> +		 * Set a OCORES_FLAG_BROKEN_IRQ to enable workaround for
> +		 * FU540-C000 SoC in polling mode interface of i2c-ocore driver.
> +		 * Else enable default polling mode interface for SIFIVE/OCORE
> +		 * device types.
> +		 */
> +		match = of_match_node(ocores_i2c_match, pdev->dev.of_node);
> +		if (match && (long)match->data == TYPE_SIFIVE_REV0)
> +			i2c->flags |= OCORES_FLAG_BROKEN_IRQ;

If it is a OCORE, IRQ is broken, so OR in OCORES_FLAG_BROKEN_IRQ.

>  
> -	if (!(i2c->flags & OCORES_FLAG_POLL)) {
> +	if (!(i2c->flags & (OCORES_FLAG_POLL | OCORES_FLAG_BROKEN_IRQ))) {
>  		ret = devm_request_irq(&pdev->dev, irq, ocores_isr, 0,
>  				       pdev->name, i2c);

Here you just need to know if you are polling. Broken IRQ does not
matter.

	Andrew

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Re: [PATCH v4 3/3] i2c-ocores: sifive: add polling mode workaround for FU540-C000 SoC

[Sagar Kadam]

Hi Andrew,

On Mon, May 20, 2019 at 6:11 PM Andrew Lunn <andrew@lunn.ch> wrote:
>
> > @@ -406,7 +416,7 @@ static int ocores_xfer(struct i2c_adapter *adap,
> >  {
> >       struct ocores_i2c *i2c = i2c_get_adapdata(adap);
> >
> > -     if (i2c->flags & OCORES_FLAG_POLL)
> > +     if ((i2c->flags & (OCORES_FLAG_POLL | OCORES_FLAG_BROKEN_IRQ)))
> >               return ocores_xfer_polling(adap, msgs, num);
> >       return ocores_xfer_core(i2c, msgs, num, false);
> >  }
>
> You are not listening to what i said. All you need to know here is
> that you must poll. It does not matter if the IRQ is broken or not.
>

Apologies for my miss-understanding. I will rectify this and submit a v5.

> >       irq = platform_get_irq(pdev, 0);
> >       if (irq == -ENXIO) {
> > -             i2c->flags |= OCORES_FLAG_POLL;
>
> If there is no interrupt, you need to poll. So keep this line.

Will retain this.

> > +             /*
> > +              * Set a OCORES_FLAG_BROKEN_IRQ to enable workaround for
> > +              * FU540-C000 SoC in polling mode interface of i2c-ocore driver.
> > +              * Else enable default polling mode interface for SIFIVE/OCORE
> > +              * device types.
> > +              */
> > +             match = of_match_node(ocores_i2c_match, pdev->dev.of_node);
> > +             if (match && (long)match->data == TYPE_SIFIVE_REV0)
> > +                     i2c->flags |= OCORES_FLAG_BROKEN_IRQ;
>
> If it is a OCORE, IRQ is broken, so OR in OCORES_FLAG_BROKEN_IRQ.

Got it, as device type SIFIVE is based on OCORE's re-implementation,
will OR in the broken IRQ flag and submit a v5.

> >
> > -     if (!(i2c->flags & OCORES_FLAG_POLL)) {
> > +     if (!(i2c->flags & (OCORES_FLAG_POLL | OCORES_FLAG_BROKEN_IRQ))) {
> >               ret = devm_request_irq(&pdev->dev, irq, ocores_isr, 0,
> >                                      pdev->name, i2c);
>
> Here you just need to know if you are polling. Broken IRQ does not
> matter.
>
>         Andrew

Thanks & Regards,
Sagar

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