From: Chris Packham <chris.packham@alliedtelesis.co.nz> Date: 2021-05-11 21:21:06
The P2040/P2041 has an erratum where the i2c recovery scheme
documented in the reference manual (and currently implemented
in the i2c-mpc.c driver) does not work. The errata document
provides an alternative that does work. This series implements
that alternative and uses a property in the devicetree to
decide when the alternative mechanism is needed.
Chris Packham (4):
dt-bindings: i2c: mpc: Add fsl,i2c-erratum-a004447 flag
powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P2041 i2c
controllers
powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P1010 i2c
controllers
i2c: mpc: implement erratum A-004447 workaround
.../devicetree/bindings/i2c/i2c-mpc.yaml | 7 ++
arch/powerpc/boot/dts/fsl/p1010si-post.dtsi | 8 ++
arch/powerpc/boot/dts/fsl/p2041si-post.dtsi | 16 ++++
drivers/i2c/busses/i2c-mpc.c | 81 ++++++++++++++++++-
4 files changed, 110 insertions(+), 2 deletions(-)
--
2.31.1
From: Chris Packham <chris.packham@alliedtelesis.co.nz> Date: 2021-05-11 21:21:03
Document the fsl,i2c-erratum-a004447 flag which indicates the presence
of an i2c erratum on some QorIQ SoCs.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Acked-by: Rob Herring <robh@kernel.org>
---
Notes:
Changes in v3:
- Add Ack from Rob
Documentation/devicetree/bindings/i2c/i2c-mpc.yaml | 7 +++++++
1 file changed, 7 insertions(+)
@@ -46,6 +46,13 @@ properties:description:|I2C bus timeout in microseconds+fsl,i2c-erratum-a004447:+$ref:/schemas/types.yaml#/definitions/flag+description:|+Indicates the presence of QorIQ erratum A-004447, which+says that the standard i2c recovery scheme mechanism does+not work and an alternate implementation is needed.+required:-compatible-reg
From: Chris Packham <chris.packham@alliedtelesis.co.nz> Date: 2021-05-11 21:21:03
The P2040/P2041 has an erratum where the normal i2c recovery mechanism
does not work. Implement the alternative recovery mechanism documented
in the P2040 Chip Errata Rev Q.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
Notes:
Changes in v3:
- Further code reduction in i2c_mpc_wait_sr()
Changes in v2:
- Use readb_poll_timeout instead of open-coded loop
drivers/i2c/busses/i2c-mpc.c | 81 +++++++++++++++++++++++++++++++++++-
1 file changed, 79 insertions(+), 2 deletions(-)
From: Chris Packham <chris.packham@alliedtelesis.co.nz> Date: 2021-05-11 21:21:05
The i2c controllers on the P2040/P2041 have an erratum where the
documented scheme for i2c bus recovery will not work (A-004447). A
different mechanism is needed which is documented in the P2040 Chip
Errata Rev Q (latest available at the time of writing).
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
arch/powerpc/boot/dts/fsl/p2041si-post.dtsi | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
From: Chris Packham <chris.packham@alliedtelesis.co.nz> Date: 2021-05-11 21:21:07
The i2c controllers on the P1010 have an erratum where the documented
scheme for i2c bus recovery will not work (A-004447). A different
mechanism is needed which is documented in the P1010 Chip Errata Rev L.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
Notes:
Changes in v3:
- New
arch/powerpc/boot/dts/fsl/p1010si-post.dtsi | 8 ++++++++
1 file changed, 8 insertions(+)
On Wed, 2021-05-12 at 09:20 +1200, Chris Packham wrote:
The P2040/P2041 has an erratum where the i2c recovery scheme
documented in the reference manual (and currently implemented
in the i2c-mpc.c driver) does not work. The errata document
provides an alternative that does work. This series implements
that alternative and uses a property in the devicetree to
decide when the alternative mechanism is needed.
Chris Packham (4):
dt-bindings: i2c: mpc: Add fsl,i2c-erratum-a004447 flag
powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P2041 i2c
controllers
powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P1010 i2c
controllers
i2c: mpc: implement erratum A-004447 workaround
.../devicetree/bindings/i2c/i2c-mpc.yaml | 7 ++
arch/powerpc/boot/dts/fsl/p1010si-post.dtsi | 8 ++
arch/powerpc/boot/dts/fsl/p2041si-post.dtsi | 16 ++++
drivers/i2c/busses/i2c-mpc.c | 81 ++++++++++++++++++-
4 files changed, 110 insertions(+), 2 deletions(-)
This now reminds me about the current I2C reset procedure, it didn't work for us and I came up with this one:
https://www.spinics.net/lists/linux-i2c/msg29490.html
it never got in but we are still using it.
Jocke
From: Chris Packham <Chris.Packham@alliedtelesis.co.nz> Date: 2021-05-12 01:48:52
On 12/05/21 10:10 am, Joakim Tjernlund wrote:
On Wed, 2021-05-12 at 09:20 +1200, Chris Packham wrote:
quoted
The P2040/P2041 has an erratum where the i2c recovery scheme
documented in the reference manual (and currently implemented
in the i2c-mpc.c driver) does not work. The errata document
provides an alternative that does work. This series implements
that alternative and uses a property in the devicetree to
decide when the alternative mechanism is needed.
Chris Packham (4):
dt-bindings: i2c: mpc: Add fsl,i2c-erratum-a004447 flag
powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P2041 i2c
controllers
powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P1010 i2c
controllers
i2c: mpc: implement erratum A-004447 workaround
.../devicetree/bindings/i2c/i2c-mpc.yaml | 7 ++
arch/powerpc/boot/dts/fsl/p1010si-post.dtsi | 8 ++
arch/powerpc/boot/dts/fsl/p2041si-post.dtsi | 16 ++++
drivers/i2c/busses/i2c-mpc.c | 81 ++++++++++++++++++-
4 files changed, 110 insertions(+), 2 deletions(-)
For those reading along the v2 mentioned in that thread was posted as
https://lore.kernel.org/linux-i2c/20170511122033.22471-1-joakim.tjernlund@infinera.com/
there was a bit of discussion but it seemed to die out without reaching
a conclusion.
The i2c-mpc driver is now using the generic recovery mechanism so that
addresses one bit of feedback from the original thread.
I do wonder if the reason the recovery wasn't working for your case was
because of the erratum. Do you happen to remember which SoC your issue
was on?
I've been doing my recent work with a P2040 and prior to that I did test
out the recovery on a T2081 (which isn't documented to have this
erratum) when I was re-working the driver. The "new" recovery actually
seems better but I don't have a reliably faulty i2c device so that's
only based on me writing some code to manually trigger the recovery
(using the snippet below) and observing it with an oscilloscope.
---8<---
device_attribute *attr,
}
static DEVICE_ATTR_WO(new_device);
+static ssize_t recover_store(struct device *dev, struct
device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct i2c_adapter *adap = to_i2c_adapter(dev);
+ int ret;
+
+ dev_info(dev, "Recovering bus\n");
+
+ ret = i2c_recover_bus(adap);
+ if (ret == -EOPNOTSUPP)
+ dev_info(dev, "recovery not supported\n");
+ else if (ret)
+ dev_err(dev, "recovery failed %d\n", ret);
+
+ return count;
+}
+
+static DEVICE_ATTR_WO(recover);
+
/*
* And of course let the users delete the devices they instantiated, if
* they got it wrong. This interface can only be used to delete devices
On Wed, 2021-05-12 at 01:48 +0000, Chris Packham wrote:
On 12/05/21 10:10 am, Joakim Tjernlund wrote:
quoted
On Wed, 2021-05-12 at 09:20 +1200, Chris Packham wrote:
quoted
The P2040/P2041 has an erratum where the i2c recovery scheme
documented in the reference manual (and currently implemented
in the i2c-mpc.c driver) does not work. The errata document
provides an alternative that does work. This series implements
that alternative and uses a property in the devicetree to
decide when the alternative mechanism is needed.
Chris Packham (4):
dt-bindings: i2c: mpc: Add fsl,i2c-erratum-a004447 flag
powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P2041 i2c
controllers
powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P1010 i2c
controllers
i2c: mpc: implement erratum A-004447 workaround
.../devicetree/bindings/i2c/i2c-mpc.yaml | 7 ++
arch/powerpc/boot/dts/fsl/p1010si-post.dtsi | 8 ++
arch/powerpc/boot/dts/fsl/p2041si-post.dtsi | 16 ++++
drivers/i2c/busses/i2c-mpc.c | 81 ++++++++++++++++++-
4 files changed, 110 insertions(+), 2 deletions(-)
It could only be P2010 or MPC8321, I think it was MPC8321, you could try my solution on your
CPU if you want to make sure.
I've been doing my recent work with a P2040 and prior to that I did test
out the recovery on a T2081 (which isn't documented to have this
erratum) when I was re-working the driver. The "new" recovery actually
seems better but I don't have a reliably faulty i2c device so that's
only based on me writing some code to manually trigger the recovery
(using the snippet below) and observing it with an oscilloscope.
You don't need a faulty device, just an aborted I2C read/write op.
You could force one such I2C op. by py pulling down the clock/SDA in the middle of a byte transfer.
Jocke
I've been doing my recent work with a P2040 and prior to that I did test
out the recovery on a T2081 (which isn't documented to have this
erratum) when I was re-working the driver. The "new" recovery actually
seems better but I don't have a reliably faulty i2c device so that's
only based on me writing some code to manually trigger the recovery
(using the snippet below) and observing it with an oscilloscope.
You don't need a faulty device, just an aborted I2C read/write op.
If you can wire GPIOs to the bus, you can use the I2C fault injector:
Documentation/i2c/gpio-fault-injection.rst
There are already two "incomplete transfer" injectors.
From: Chris Packham <Chris.Packham@alliedtelesis.co.nz> Date: 2021-05-20 03:37:04
On 13/05/21 3:01 am, wsa@kernel.org wrote:
quoted
quoted
I've been doing my recent work with a P2040 and prior to that I did test
out the recovery on a T2081 (which isn't documented to have this
erratum) when I was re-working the driver. The "new" recovery actually
seems better but I don't have a reliably faulty i2c device so that's
only based on me writing some code to manually trigger the recovery
(using the snippet below) and observing it with an oscilloscope.
You don't need a faulty device, just an aborted I2C read/write op.
If you can wire GPIOs to the bus, you can use the I2C fault injector:
Documentation/i2c/gpio-fault-injection.rst
There are already two "incomplete transfer" injectors.
Just giving this thread a poke. I have been looking at my options for
triggering an i2c recovery but haven't really had time to do much. I
think the best option given what I've got access to is a modified SFP
that grounds the SDA line but I need to find a system where I can attach
an oscilloscope (should be a few of these in the office when I can get
on-site).
I can confirm that when manually triggered the existing recovery and the
new erratum workaround produce what I'd expect to observe on an
oscilloscope.
I haven't explored Joakim's alternative recovery but I don't think that
should hold up these changes, any improvement to the existing recovery
can be done later as a follow-up.
For those reading along the v2 mentioned in that thread was posted as
https://lore.kernel.org/linux-i2c/20170511122033.22471-1-joakim.tjernlund@infinera.com/
there was a bit of discussion but it seemed to die out without reaching
a conclusion.
The i2c-mpc driver is now using the generic recovery mechanism so that
addresses one bit of feedback from the original thread.
Yes, and the generic recovery has been improved since then. There is an
"incomplete_write_byte" fault injector now and the generic recovery
handles it correctly meanwhile. Before, it actually could cause a write
to happen but we are sending STOPs now.
From: Wolfram Sang <wsa@kernel.org> Date: 2021-05-25 18:53:38
On Wed, May 12, 2021 at 09:20:48AM +1200, Chris Packham wrote:
The P2040/P2041 has an erratum where the i2c recovery scheme
documented in the reference manual (and currently implemented
in the i2c-mpc.c driver) does not work. The errata document
provides an alternative that does work. This series implements
that alternative and uses a property in the devicetree to
decide when the alternative mechanism is needed.
The series looks good to me. Usually, I don't take DTS patches. This
time I'd make an exception and apply all patches to for-current because
this is clearly a bugfix. For that, I'd need an ack from PPC
maintainers. Could I have those for patches 2+3?
From: Michael Ellerman <mpe@ellerman.id.au> Date: 2021-05-26 01:02:18
Chris Packham [off-list ref] writes:
The i2c controllers on the P2040/P2041 have an erratum where the
documented scheme for i2c bus recovery will not work (A-004447). A
different mechanism is needed which is documented in the P2040 Chip
Errata Rev Q (latest available at the time of writing).
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
arch/powerpc/boot/dts/fsl/p2041si-post.dtsi | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
cheers
From: Michael Ellerman <mpe@ellerman.id.au> Date: 2021-05-26 01:02:38
Chris Packham [off-list ref] writes:
The i2c controllers on the P1010 have an erratum where the documented
scheme for i2c bus recovery will not work (A-004447). A different
mechanism is needed which is documented in the P1010 Chip Errata Rev L.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
Notes:
Changes in v3:
- New
arch/powerpc/boot/dts/fsl/p1010si-post.dtsi | 8 ++++++++
1 file changed, 8 insertions(+)
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
cheers
From: Michael Ellerman <mpe@ellerman.id.au> Date: 2021-05-26 01:02:53
Wolfram Sang [off-list ref] writes:
On Wed, May 12, 2021 at 09:20:48AM +1200, Chris Packham wrote:
quoted
The P2040/P2041 has an erratum where the i2c recovery scheme
documented in the reference manual (and currently implemented
in the i2c-mpc.c driver) does not work. The errata document
provides an alternative that does work. This series implements
that alternative and uses a property in the devicetree to
decide when the alternative mechanism is needed.
The series looks good to me. Usually, I don't take DTS patches. This
time I'd make an exception and apply all patches to for-current because
this is clearly a bugfix. For that, I'd need an ack from PPC
maintainers. Could I have those for patches 2+3?
From: Wolfram Sang <wsa@kernel.org> Date: 2021-05-27 19:53:41
On Wed, May 26, 2021 at 11:02:45AM +1000, Michael Ellerman wrote:
Wolfram Sang [off-list ref] writes:
quoted
On Wed, May 12, 2021 at 09:20:48AM +1200, Chris Packham wrote:
quoted
The P2040/P2041 has an erratum where the i2c recovery scheme
documented in the reference manual (and currently implemented
in the i2c-mpc.c driver) does not work. The errata document
provides an alternative that does work. This series implements
that alternative and uses a property in the devicetree to
decide when the alternative mechanism is needed.
The series looks good to me. Usually, I don't take DTS patches. This
time I'd make an exception and apply all patches to for-current because
this is clearly a bugfix. For that, I'd need an ack from PPC
maintainers. Could I have those for patches 2+3?