* [RFC] i2c: Providing hooks for i2c multimaster bus arbitration.
@ 2013-02-04 9:03 Yuvaraj Kumar C D
2013-02-04 11:13 ` Yuvaraj Kumar
` (3 more replies)
0 siblings, 4 replies; 10+ messages in thread
From: Yuvaraj Kumar C D @ 2013-02-04 9:03 UTC (permalink / raw)
To: linux-i2c, linux-samsung-soc, linux-arm-kernel, w.sang
Cc: broonie, ch.naveen, sjg, grundler, Yuvaraj Kumar C D
This RFC patch is w.r.t multimaster bus arbitration which is already
being discussing in the mainline.
This patch provides hooks for the i2c multimaster bus arbitration
and to have the arbitration parameters.
Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd@samsung.com>
---
drivers/i2c/i2c-core.c | 13 ++++++++++++-
include/linux/i2c.h | 12 ++++++++++++
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index e388590..ed89fc8 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -1408,18 +1408,29 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
(msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : "");
}
#endif
+ if (adap->mm_arbit_algo) {
+ ret = adap->mm_arbit_algo->i2c_mm_bus_get(adap);
+ if (ret)
+ /* I2C bus under control of another master. */
+ return -EAGAIN;
+ }
if (in_atomic() || irqs_disabled()) {
ret = i2c_trylock_adapter(adap);
- if (!ret)
+ if (!ret && adap->mm_arbit_algo) {
+ adap->mm_arbit_algo->i2c_mm_bus_release(adap);
+
/* I2C activity is ongoing. */
return -EAGAIN;
+ }
} else {
i2c_lock_adapter(adap);
}
ret = __i2c_transfer(adap, msgs, num);
i2c_unlock_adapter(adap);
+ if (adap->mm_arbit_algo)
+ adap->mm_arbit_algo->i2c_mm_bus_release(adap);
return ret;
} else {
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index d0c4db7..61fbfe3 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -371,6 +371,17 @@ struct i2c_algorithm {
};
/*
+ *This struct provides hooks for i2c multi-master arbitration needs.
+ */
+struct i2c_mm_arbitration {
+ void *arbitration_data;
+
+ /* Should return 0 if mastership could be successfully established */
+ int (*i2c_mm_bus_get)(struct i2c_adapter *adap);
+ void (*i2c_mm_bus_release)(struct i2c_adapter *adap);
+};
+
+/*
* i2c_adapter is the structure used to identify a physical i2c bus along
* with the access algorithms necessary to access it.
*/
@@ -393,6 +404,7 @@ struct i2c_adapter {
struct mutex userspace_clients_lock;
struct list_head userspace_clients;
+ struct i2c_mm_arbitration *mm_arbit_algo;
};
#define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
--
1.7.9.5
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [RFC] i2c: Providing hooks for i2c multimaster bus arbitration.
2013-02-04 9:03 [RFC] i2c: Providing hooks for i2c multimaster bus arbitration Yuvaraj Kumar C D
@ 2013-02-04 11:13 ` Yuvaraj Kumar
2013-02-06 0:23 ` Doug Anderson
` (2 subsequent siblings)
3 siblings, 0 replies; 10+ messages in thread
From: Yuvaraj Kumar @ 2013-02-04 11:13 UTC (permalink / raw)
To: linux-i2c, linux-samsung-soc, linux-arm-kernel, w.sang
Cc: broonie, ch.naveen, sjg, grundler, Yuvaraj Kumar C D
Below are the links on multi master bus arbitration where it has been
discussing.
http://comments.gmane.org/gmane.linux.kernel/1410276
http://www.kernelhub.org/?msg=179505&p=2
On Mon, Feb 4, 2013 at 2:33 PM, Yuvaraj Kumar C D <yuvaraj.cd@gmail.com> wrote:
> This RFC patch is w.r.t multimaster bus arbitration which is already
> being discussing in the mainline.
> This patch provides hooks for the i2c multimaster bus arbitration
> and to have the arbitration parameters.
>
> Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd@samsung.com>
> ---
> drivers/i2c/i2c-core.c | 13 ++++++++++++-
> include/linux/i2c.h | 12 ++++++++++++
> 2 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index e388590..ed89fc8 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -1408,18 +1408,29 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> (msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : "");
> }
> #endif
> + if (adap->mm_arbit_algo) {
> + ret = adap->mm_arbit_algo->i2c_mm_bus_get(adap);
> + if (ret)
> + /* I2C bus under control of another master. */
> + return -EAGAIN;
> + }
>
> if (in_atomic() || irqs_disabled()) {
> ret = i2c_trylock_adapter(adap);
> - if (!ret)
> + if (!ret && adap->mm_arbit_algo) {
> + adap->mm_arbit_algo->i2c_mm_bus_release(adap);
> +
> /* I2C activity is ongoing. */
> return -EAGAIN;
> + }
> } else {
> i2c_lock_adapter(adap);
> }
>
> ret = __i2c_transfer(adap, msgs, num);
> i2c_unlock_adapter(adap);
> + if (adap->mm_arbit_algo)
> + adap->mm_arbit_algo->i2c_mm_bus_release(adap);
>
> return ret;
> } else {
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index d0c4db7..61fbfe3 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -371,6 +371,17 @@ struct i2c_algorithm {
> };
>
> /*
> + *This struct provides hooks for i2c multi-master arbitration needs.
> + */
> +struct i2c_mm_arbitration {
> + void *arbitration_data;
> +
> + /* Should return 0 if mastership could be successfully established */
> + int (*i2c_mm_bus_get)(struct i2c_adapter *adap);
> + void (*i2c_mm_bus_release)(struct i2c_adapter *adap);
> +};
> +
> +/*
> * i2c_adapter is the structure used to identify a physical i2c bus along
> * with the access algorithms necessary to access it.
> */
> @@ -393,6 +404,7 @@ struct i2c_adapter {
>
> struct mutex userspace_clients_lock;
> struct list_head userspace_clients;
> + struct i2c_mm_arbitration *mm_arbit_algo;
> };
> #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
>
> --
> 1.7.9.5
>
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [RFC] i2c: Providing hooks for i2c multimaster bus arbitration.
2013-02-04 9:03 [RFC] i2c: Providing hooks for i2c multimaster bus arbitration Yuvaraj Kumar C D
2013-02-04 11:13 ` Yuvaraj Kumar
@ 2013-02-06 0:23 ` Doug Anderson
[not found] ` <CAD=FV=VQywwQ3YAFb=1qFmd3UEW39Xu=ok6fdjhvBXdwOQOa1Q@mail.gmail.com>
2013-02-10 18:17 ` Wolfram Sang
3 siblings, 0 replies; 10+ messages in thread
From: Doug Anderson @ 2013-02-06 0:23 UTC (permalink / raw)
To: Yuvaraj Kumar C D
Cc: linux-i2c@vger.kernel.org, linux-samsung-soc,
linux-arm-kernel@lists.infradead.org, Wolfram Sang,
Grant Grundler, Yuvaraj Kumar C D, Simon Glass, Mark Brown,
naveen krishna, Grant Likely
Yavaraj,
On Mon, Feb 4, 2013 at 1:03 AM, Yuvaraj Kumar C D <yuvaraj.cd@gmail.com> wrote:
>
> This RFC patch is w.r.t multimaster bus arbitration which is already
> being discussing in the mainline.
> This patch provides hooks for the i2c multimaster bus arbitration
> and to have the arbitration parameters.
I may have missed something in all the threads, but my recollection
was that the request was that this should be implemented without
touching the i2c core code. Your patch modifies the i2c core code.
My impression was that the best solution was to use the infrastructure
in place for i2c multiplexing. ...but in your case you would only
multiplex one thing. This was suggested by Grant Likely and seems the
cleanest...
[apologies for double-email; darn gmail and HTML email]
-Doug
^ permalink raw reply [flat|nested] 10+ messages in thread[parent not found: <CAD=FV=VQywwQ3YAFb=1qFmd3UEW39Xu=ok6fdjhvBXdwOQOa1Q@mail.gmail.com>]
* Re: [RFC] i2c: Providing hooks for i2c multimaster bus arbitration.
2013-02-04 9:03 [RFC] i2c: Providing hooks for i2c multimaster bus arbitration Yuvaraj Kumar C D
` (2 preceding siblings ...)
[not found] ` <CAD=FV=VQywwQ3YAFb=1qFmd3UEW39Xu=ok6fdjhvBXdwOQOa1Q@mail.gmail.com>
@ 2013-02-10 18:17 ` Wolfram Sang
2013-02-11 23:53 ` Doug Anderson
3 siblings, 1 reply; 10+ messages in thread
From: Wolfram Sang @ 2013-02-10 18:17 UTC (permalink / raw)
To: Yuvaraj Kumar C D
Cc: linux-i2c, linux-samsung-soc, linux-arm-kernel, broonie,
ch.naveen, sjg, grundler, Yuvaraj Kumar C D
On Mon, Feb 04, 2013 at 02:33:15PM +0530, Yuvaraj Kumar C D wrote:
> This RFC patch is w.r.t multimaster bus arbitration which is already
> being discussing in the mainline.
> This patch provides hooks for the i2c multimaster bus arbitration
> and to have the arbitration parameters.
I still haven't understood why the arbitration specified in the I2C
standard is not enough for you. Or what you would need to make use of
it.
Thanks,
Wolfram
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [RFC] i2c: Providing hooks for i2c multimaster bus arbitration.
2013-02-10 18:17 ` Wolfram Sang
@ 2013-02-11 23:53 ` Doug Anderson
2013-02-12 0:17 ` Simon Glass
0 siblings, 1 reply; 10+ messages in thread
From: Doug Anderson @ 2013-02-11 23:53 UTC (permalink / raw)
To: Wolfram Sang
Cc: Yuvaraj Kumar C D, Yuvaraj Kumar C D, linux-samsung-soc,
Grant Grundler, Simon Glass, Mark Brown,
linux-i2c@vger.kernel.org, naveen krishna,
linux-arm-kernel@lists.infradead.org
Wolfram,
On Sun, Feb 10, 2013 at 10:17 AM, Wolfram Sang <w.sang@pengutronix.de> wrote:
> On Mon, Feb 04, 2013 at 02:33:15PM +0530, Yuvaraj Kumar C D wrote:
>> This RFC patch is w.r.t multimaster bus arbitration which is already
>> being discussing in the mainline.
>> This patch provides hooks for the i2c multimaster bus arbitration
>> and to have the arbitration parameters.
>
> I still haven't understood why the arbitration specified in the I2C
> standard is not enough for you. Or what you would need to make use of
> it.
At the moment perhaps the strongest argument for why this particular
arbitration scheme is needed is that's what the EC (embedded
controller) on the ARM Chromebook uses. There have been several
arguments in-house about whether this was the most ideal way to
structure things, but that's what we shipped with. Thus, if we want
to be able to talk to i2c devices on this bus (contains the keyboard,
battery, and a bunch of power switches) we need something in the
system that implements this arbitration scheme.
As a side note: I'm trying to code up a quick arbitrator now using the
muxing framework as Grant suggested. I will play with this and post
it if I can get it to work. It's quite short so far.
-Doug
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [RFC] i2c: Providing hooks for i2c multimaster bus arbitration.
2013-02-11 23:53 ` Doug Anderson
@ 2013-02-12 0:17 ` Simon Glass
[not found] ` <CAPnjgZ3HnXDp9ErsbZEfpc-NexuAt1C5cUWbFn=BW2TMGiMJEg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
0 siblings, 1 reply; 10+ messages in thread
From: Simon Glass @ 2013-02-12 0:17 UTC (permalink / raw)
To: Doug Anderson
Cc: Wolfram Sang, Yuvaraj Kumar C D, Yuvaraj Kumar C D,
linux-samsung-soc, Grant Grundler, Mark Brown,
linux-i2c@vger.kernel.org, naveen krishna,
linux-arm-kernel@lists.infradead.org
On Mon, Feb 11, 2013 at 3:53 PM, Doug Anderson <dianders@chromium.org> wrote:
> Wolfram,
>
> On Sun, Feb 10, 2013 at 10:17 AM, Wolfram Sang <w.sang@pengutronix.de> wrote:
>> On Mon, Feb 04, 2013 at 02:33:15PM +0530, Yuvaraj Kumar C D wrote:
>>> This RFC patch is w.r.t multimaster bus arbitration which is already
>>> being discussing in the mainline.
>>> This patch provides hooks for the i2c multimaster bus arbitration
>>> and to have the arbitration parameters.
>>
>> I still haven't understood why the arbitration specified in the I2C
>> standard is not enough for you. Or what you would need to make use of
>> it.
>
> At the moment perhaps the strongest argument for why this particular
> arbitration scheme is needed is that's what the EC (embedded
> controller) on the ARM Chromebook uses. There have been several
> arguments in-house about whether this was the most ideal way to
> structure things, but that's what we shipped with. Thus, if we want
> to be able to talk to i2c devices on this bus (contains the keyboard,
> battery, and a bunch of power switches) we need something in the
> system that implements this arbitration scheme.
>
There was some discussion about using the built-in I2C multi-master
support but no one had had a good experience getting it to work
reliably in a real system so we ended up deciding not to rely on this.
> As a side note: I'm trying to code up a quick arbitrator now using the
> muxing framework as Grant suggested. I will play with this and post
> it if I can get it to work. It's quite short so far.
>
> -Doug
^ permalink raw reply [flat|nested] 10+ messages in thread
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2013-02-04 9:03 [RFC] i2c: Providing hooks for i2c multimaster bus arbitration Yuvaraj Kumar C D
2013-02-04 11:13 ` Yuvaraj Kumar
2013-02-06 0:23 ` Doug Anderson
[not found] ` <CAD=FV=VQywwQ3YAFb=1qFmd3UEW39Xu=ok6fdjhvBXdwOQOa1Q@mail.gmail.com>
[not found] ` <CAD=FV=VQywwQ3YAFb=1qFmd3UEW39Xu=ok6fdjhvBXdwOQOa1Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-02-06 5:28 ` Yuvaraj Kumar
2013-02-06 5:33 ` Yuvaraj Kumar
2013-02-06 6:00 ` Simon Glass
2013-02-10 18:17 ` Wolfram Sang
2013-02-11 23:53 ` Doug Anderson
2013-02-12 0:17 ` Simon Glass
[not found] ` <CAPnjgZ3HnXDp9ErsbZEfpc-NexuAt1C5cUWbFn=BW2TMGiMJEg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-02-12 10:03 ` Wolfram Sang
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