[PATCH v3 0/1] fix i2c polling mode workaround for FU540-C000 SoC

[PATCH v3 0/1] fix i2c polling mode workaround for FU540-C000 SoC

[Sagar Shrikant Kadam]

The polling mode workaround for the FU540-C000 on HiFive Unleashed A00
board was added earlier. The logic for this seems to work only in case
the interrupt property was missing/not added into the i2c0 device node.

Here we address this issue by identifying the SOC based on compatibility
string and set the master xfer's to polling mode if it's the FU540-C000
SoC.

The fix has been tested on Linux 5.9.0-rc8 with a PMOD based RTCC sensor
connected to I2C pins J1 header of the board. Log for reference

# uname -a
Linux buildroot 5.9.0-rc8-00001-g9da7791 #1 SMP Fri Oct 9 07:56:13 PDT 2020 riscv64 GNU/Linux
# i2cdetect -y 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- 57 -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 6f
70: -- -- -- -- -- -- -- --
# i2cget 0 0x57 0 b -y
0xa5
# i2cset 0 0x57 0 0x9f b -y
# i2cget 0 0x57 0 b -y
0x9f
# i2cget 0 0x57 1 b -y
0xff
# i2cset 0 0x57 1 0xa9 b -y
# i2cget 0 0x57 1 b -y
0xa9
# i2cget 0 0x6f 0x20 b -y
0x98
# i2cset 0 0x6f 0x20 0xa5 b -y
# i2cget 0 0x6f 0x20 b -y
0xa5
# i2cget 0 0x6f 0x5f b -y
0x55
# i2cset 0 0x6f 0x5f 0x5a b -y
# i2cget 0 0x6f 0x5f b -y
0x5a
#

Without the fix here, it's observed that "i2cdetect -y 0"
turns the system unresponsive, with CPU stall messages.

Patch History:
===============================
V3:
-Rectified typo as suggested here:
 https://lkml.org/lkml/2020/10/9/902

V2: 
-Incorporated changes as suggested by Peter Kosgaard
 https://lkml.org/lkml/2020/10/8/663

V1: Base version



Sagar Shrikant Kadam (1):
  i2c: ocores: fix polling mode workaround on FU540-C000 SoC

 drivers/i2c/busses/i2c-ocores.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

-- 
2.7.4


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[PATCH v3 1/1] i2c: ocores: fix polling mode workaround on FU540-C000 SoC

[Sagar Shrikant Kadam]

The FU540-C000 has a broken IRQ and support was added earlier
so that it will operate in polling mode, but seems to work only
in case interrupts property is missing from the i2c0 dt-node.
This should not be the case and the driver should handle polling
mode with the interrupt property present in i2c0 node of the
device tree.
So check if it's the FU540-C000 soc and enable polling mode master
xfers, as the IRQ for this chip is broken.

Fixes commit c45d4ba86731 ("i2c: ocores: add polling mode workaround
for Sifive FU540-C000 SoC")

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
 drivers/i2c/busses/i2c-ocores.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
index f5fc75b..1dab02d 100644
--- a/drivers/i2c/busses/i2c-ocores.c
+++ b/drivers/i2c/busses/i2c-ocores.c
@@ -686,17 +686,21 @@ static int ocores_i2c_probe(struct platform_device *pdev)
 
 	init_waitqueue_head(&i2c->wait);
 
+	/*
+	 * Set OCORES_FLAG_BROKEN_IRQ to enable workaround for
+	 * FU540-C000 SoC in polling mode.
+	 * Since the SoC does have interrupt its dt has the interrupt
+	 * defined but it should be bypassed in driver as this SoC has
+	 * a broken IRQ, hence update the master_xfer to use polling
+	 * transfers.
+	 */
+	if (of_device_is_compatible(pdev->dev.of_node,
+				    "sifive,fu540-c000-i2c"))
+		i2c->flags |= OCORES_FLAG_BROKEN_IRQ;
+
 	irq = platform_get_irq(pdev, 0);
-	if (irq == -ENXIO) {
+	if (i2c->flags & OCORES_FLAG_BROKEN_IRQ || irq == -ENXIO) {
 		ocores_algorithm.master_xfer = ocores_xfer_polling;
-
-		/*
-		 * Set in OCORES_FLAG_BROKEN_IRQ to enable workaround for
-		 * FU540-C000 SoC in polling mode.
-		 */
-		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 {
 		if (irq < 0)
 			return irq;
-- 
2.7.4


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Re: [PATCH v3 1/1] i2c: ocores: fix polling mode workaround on FU540-C000 SoC

[Peter Korsgaard]

>>>>> "Sagar" == Sagar Shrikant Kadam <sagar.kadam@sifive.com> writes:

 > The FU540-C000 has a broken IRQ and support was added earlier
 > so that it will operate in polling mode, but seems to work only
 > in case interrupts property is missing from the i2c0 dt-node.
 > This should not be the case and the driver should handle polling
 > mode with the interrupt property present in i2c0 node of the
 > device tree.
 > So check if it's the FU540-C000 soc and enable polling mode master
 > xfers, as the IRQ for this chip is broken.

 > Fixes commit c45d4ba86731 ("i2c: ocores: add polling mode workaround
 > for Sifive FU540-C000 SoC")

 > Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
 > ---
 >  drivers/i2c/busses/i2c-ocores.c | 22 +++++++++++++---------
 >  1 file changed, 13 insertions(+), 9 deletions(-)

 > diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
 > index f5fc75b..1dab02d 100644
 > --- a/drivers/i2c/busses/i2c-ocores.c
 > +++ b/drivers/i2c/busses/i2c-ocores.c
 > @@ -686,17 +686,21 @@ static int ocores_i2c_probe(struct platform_device *pdev)
 
 >  	init_waitqueue_head(&i2c->wait);
 
 > +	/*
 > +	 * Set OCORES_FLAG_BROKEN_IRQ to enable workaround for
 > +	 * FU540-C000 SoC in polling mode.
 > +	 * Since the SoC does have interrupt its dt has the interrupt
 > +	 * defined but it should be bypassed in driver as this SoC has

NIT: Looks like there some commas missing and the wording sounds a bit
odd to me. What about E.G.:

     /*
      * Since the SoC does have an interrupt, its DT has an interrupt
      * property - But this should be bypassed as the IRQ logic in this
      * SoC is broken.
      */

 > +	 * a broken IRQ, hence update the master_xfer to use polling
 > +	 * transfers.
 > +	 */
 > +	if (of_device_is_compatible(pdev->dev.of_node,
 > +				    "sifive,fu540-c000-i2c"))
 > +		i2c->flags |= OCORES_FLAG_BROKEN_IRQ;
 > +
 >  	irq = platform_get_irq(pdev, 0);
 > -	if (irq == -ENXIO) {
 > +	if (i2c->flags & OCORES_FLAG_BROKEN_IRQ || irq == -ENXIO) {


Alternatively you can move it after the irq = platform_get_irq(pdev, 0)
line and just clear irq, E.G.:

irq = platform_get_irq(pdev, 0);

if (of_device_is_compatible(..)) {
   i2c->flags |= OCORES_FLAG_BROKEN_IRQ;
   irq = -ENXIO;
}

if (irq == -ENXIO) {
..

-- 
Bye, Peter Korsgaard

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RE: [PATCH v3 1/1] i2c: ocores: fix polling mode workaround on FU540-C000 SoC

[Sagar Kadam]

Hello Peter,

> -----Original Message-----
> From: Peter Korsgaard <jacmet@gmail.com> On Behalf Of Peter Korsgaard
> Sent: Thursday, October 15, 2020 8:19 PM
> To: Sagar Kadam <sagar.kadam@openfive.com>
> Cc: linux-kernel@vger.kernel.org; linux-riscv@lists.infradead.org; linux-
> i2c@vger.kernel.org; andrew@lunn.ch; Paul Walmsley ( Sifive)
> <paul.walmsley@sifive.com>; palmer@dabbelt.com;
> aou@eecs.berkeley.edu
> Subject: Re: [PATCH v3 1/1] i2c: ocores: fix polling mode workaround on
> FU540-C000 SoC
> 
> [External Email] Do not click links or attachments unless you recognize the
> sender and know the content is safe
> 
> >>>>> "Sagar" == Sagar Shrikant Kadam <sagar.kadam@sifive.com> writes:
> 
>  > The FU540-C000 has a broken IRQ and support was added earlier
>  > so that it will operate in polling mode, but seems to work only
>  > in case interrupts property is missing from the i2c0 dt-node.
>  > This should not be the case and the driver should handle polling
>  > mode with the interrupt property present in i2c0 node of the
>  > device tree.
>  > So check if it's the FU540-C000 soc and enable polling mode master
>  > xfers, as the IRQ for this chip is broken.
> 
>  > Fixes commit c45d4ba86731 ("i2c: ocores: add polling mode workaround
>  > for Sifive FU540-C000 SoC")
> 
>  > Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
>  > ---
>  >  drivers/i2c/busses/i2c-ocores.c | 22 +++++++++++++---------
>  >  1 file changed, 13 insertions(+), 9 deletions(-)
> 
>  > diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-
> ocores.c
>  > index f5fc75b..1dab02d 100644
>  > --- a/drivers/i2c/busses/i2c-ocores.c
>  > +++ b/drivers/i2c/busses/i2c-ocores.c
>  > @@ -686,17 +686,21 @@ static int ocores_i2c_probe(struct
> platform_device *pdev)
> 
>  >      init_waitqueue_head(&i2c->wait);
> 
>  > +    /*
>  > +     * Set OCORES_FLAG_BROKEN_IRQ to enable workaround for
>  > +     * FU540-C000 SoC in polling mode.
>  > +     * Since the SoC does have interrupt its dt has the interrupt
>  > +     * defined but it should be bypassed in driver as this SoC has
> 
> NIT: Looks like there some commas missing and the wording sounds a bit
> odd to me. What about E.G.:
> 
Sorry for the confusing wordings here.
>      /*
>       * Since the SoC does have an interrupt, its DT has an interrupt
>       * property - But this should be bypassed as the IRQ logic in this
>       * SoC is broken.
>       */
> 
I will replace mine with your suggested one.

>  > +     * a broken IRQ, hence update the master_xfer to use polling
>  > +     * transfers.
>  > +     */
>  > +    if (of_device_is_compatible(pdev->dev.of_node,
>  > +                                "sifive,fu540-c000-i2c"))
>  > +            i2c->flags |= OCORES_FLAG_BROKEN_IRQ;
>  > +
>  >      irq = platform_get_irq(pdev, 0);
>  > -    if (irq == -ENXIO) {
>  > +    if (i2c->flags & OCORES_FLAG_BROKEN_IRQ || irq == -ENXIO) {
> 
> 
> Alternatively you can move it after the irq = platform_get_irq(pdev, 0)
> line and just clear irq, E.G.:
> 
> irq = platform_get_irq(pdev, 0);
> 
> if (of_device_is_compatible(..)) {
>    i2c->flags |= OCORES_FLAG_BROKEN_IRQ;
>    irq = -ENXIO;
> }
> 
Yeah..
This is a better alternative implementation.
I will push v4 with this.

Thanks & BR,
Sagar

> if (irq == -ENXIO) {
> ..
> 
> --
> Bye, Peter Korsgaard

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