[PATCH] drm/radeon: warn users when hw_i2c is enabled

[PATCH] drm/radeon: warn users when hw_i2c is enabled

[Alex Deucher]

The hw i2c engines are disabled by default as the
current implementation is still experimental.  Print
a warning when users enable it so that it's obvious
when the option is enabled.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
---
 drivers/gpu/drm/radeon/radeon_i2c.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_i2c.c b/drivers/gpu/drm/radeon/radeon_i2c.c
index fc60b74..74bfbf8 100644
--- a/drivers/gpu/drm/radeon/radeon_i2c.c
+++ b/drivers/gpu/drm/radeon/radeon_i2c.c
@@ -1020,6 +1020,9 @@ void radeon_i2c_destroy(struct radeon_i2c_chan *i2c)
 /* Add the default buses */
 void radeon_i2c_init(struct radeon_device *rdev)
 {
+	if (radeon_hw_i2c == 1)
+		DRM_INFO("hw_i2c forced on, you may experience display detection problems!\n");
+
 	if (rdev->is_atom_bios)
 		radeon_atombios_i2c_init(rdev);
 	else
-- 
1.8.3.1

Re: [PATCH] drm/radeon: warn users when hw_i2c is enabled

[Christian König]

Am 07.01.2014 16:14, schrieb Alex Deucher:
> The hw i2c engines are disabled by default as the
> current implementation is still experimental.  Print
> a warning when users enable it so that it's obvious
> when the option is enabled.
>
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> Cc: stable@vger.kernel.org

Reviewed-by: Christian König <christian.koenig@amd.com>

> ---
>   drivers/gpu/drm/radeon/radeon_i2c.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_i2c.c b/drivers/gpu/drm/radeon/radeon_i2c.c
> index fc60b74..74bfbf8 100644
> --- a/drivers/gpu/drm/radeon/radeon_i2c.c
> +++ b/drivers/gpu/drm/radeon/radeon_i2c.c
> @@ -1020,6 +1020,9 @@ void radeon_i2c_destroy(struct radeon_i2c_chan *i2c)
>   /* Add the default buses */
>   void radeon_i2c_init(struct radeon_device *rdev)
>   {
> +	if (radeon_hw_i2c == 1)
> +		DRM_INFO("hw_i2c forced on, you may experience display detection problems!\n");
> +
>   	if (rdev->is_atom_bios)
>   		radeon_atombios_i2c_init(rdev);
>   	else

Re: [PATCH] drm/radeon: warn users when hw_i2c is enabled

[Grigori Goronzy]

On 07.01.2014 16:14, Alex Deucher wrote:
> The hw i2c engines are disabled by default as the
> current implementation is still experimental.  Print
> a warning when users enable it so that it's obvious
> when the option is enabled.
>

Does hardware I2C actually have any advantage in the DDC use case? 
AFAICT it's only transferring small amounts of data and mostly on 
display connect events, so not very often.

Best regards
Grigori

Re: [PATCH] drm/radeon: warn users when hw_i2c is enabled

[Alex Deucher]

On Tue, Jan 7, 2014 at 10:58 AM, Grigori Goronzy <greg@chown.ath.cx> wrote:
> On 07.01.2014 16:14, Alex Deucher wrote:
>>
>> The hw i2c engines are disabled by default as the
>> current implementation is still experimental.  Print
>> a warning when users enable it so that it's obvious
>> when the option is enabled.
>>
>
> Does hardware I2C actually have any advantage in the DDC use case? AFAICT
> it's only transferring small amounts of data and mostly on display connect
> events, so not very often.

It's lower CPU usage compared to bit-banging and can generate
interrupts if you want to do something else while it fetches the EDID.

Alex

Re: [PATCH] drm/radeon: warn users when hw_i2c is enabled

[Rafał Miłecki]

2014/1/7 Alex Deucher <alexdeucher@gmail.com>:
> +       if (radeon_hw_i2c == 1)
> +               DRM_INFO("hw_i2c forced on, you may experience display detection problems!\n");

What about simple
if (radeon_hw_i2c)
? Values 2, 3, ... also enable i2c.

Re: [PATCH] drm/radeon: warn users when hw_i2c is enabled

[Alex Deucher]

On Tue, Jan 7, 2014 at 11:16 AM, Rafał Miłecki <zajec5@gmail.com> wrote:
> 2014/1/7 Alex Deucher <alexdeucher@gmail.com>:
>> +       if (radeon_hw_i2c == 1)
>> +               DRM_INFO("hw_i2c forced on, you may experience display detection problems!\n");
>
> What about simple
> if (radeon_hw_i2c)
> ? Values 2, 3, ... also enable i2c.

Updated patch sent.  thanks!

Alex