Re: [RFC 11/14] drm/i915: Enable MIPI display self refresh mode

["Singh, Gaurav K" <gaurav.k.singh@intel.com>]

On 6/15/2015 4:03 PM, Daniel Vetter wrote:
> On Sat, Jun 13, 2015 at 12:24:57PM +0530, Mohan Marimuthu, Yogesh wrote:
>>
>> On 5/29/2015 10:51 PM, Daniel Vetter wrote:
>>> On Fri, May 29, 2015 at 04:07:03PM +0530, Gaurav K Singh wrote:
>>>> During enable sequence for MIPI encoder in command mode, enable
>>>> MIPI display self-refresh mode bit in Pipe Ctrl reg.
>>>>
>>>> Signed-off-by: Gaurav K Singh <gaurav.k.singh@intel.com>
>>>> Signed-off-by: Yogesh Mohan Marimuthu <yogesh.mohan.marimuthu@intel.com>
>>>> Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
>>>> ---
>>>>   drivers/gpu/drm/i915/intel_display.c |   15 +++++++++++++++
>>>>   1 file changed, 15 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
>>>> index cab2ac8..fc84313 100644
>>>> --- a/drivers/gpu/drm/i915/intel_display.c
>>>> +++ b/drivers/gpu/drm/i915/intel_display.c
>>>> @@ -44,6 +44,7 @@
>>>>   #include <drm/drm_plane_helper.h>
>>>>   #include <drm/drm_rect.h>
>>>>   #include <linux/dma_remapping.h>
>>>> +#include "intel_dsi.h"
>>>>   /* Primary plane formats supported by all gen */
>>>>   #define COMMON_PRIMARY_FORMATS \
>>>> @@ -2110,6 +2111,8 @@ static void intel_enable_pipe(struct intel_crtc *crtc)
>>>>   {
>>>>   	struct drm_device *dev = crtc->base.dev;
>>>>   	struct drm_i915_private *dev_priv = dev->dev_private;
>>>> +	struct intel_encoder *encoder;
>>>> +	struct intel_dsi *intel_dsi;
>>>>   	enum pipe pipe = crtc->pipe;
>>>>   	enum transcoder cpu_transcoder = intel_pipe_to_cpu_transcoder(dev_priv,
>>>>   								      pipe);
>>>> @@ -2154,6 +2157,18 @@ static void intel_enable_pipe(struct intel_crtc *crtc)
>>>>   		return;
>>>>   	}
>>>> +	for_each_encoder_on_crtc(dev, &crtc->base, encoder) {
>>>> +		if (encoder->type == INTEL_OUTPUT_DSI) {
>>>> +			intel_dsi = enc_to_intel_dsi(&encoder->base);
>>>> +			if (intel_dsi && (intel_dsi->operation_mode ==
>>>> +			    INTEL_DSI_COMMAND_MODE)) {
>>>> +				val = val | PIPECONF_MIPI_DSR_ENABLE;
>>>> +				I915_WRITE(reg, val);
>>>> +			}
>>>> +			break;
>>>> +		}
>>>> +	}
>>> When we have these kind of encoder/crtc state depencies we resolve them by
>>> adding a bit of state to intel_crtc_state which is set as needed in the
>>> encoder's compute_config callback. Then all you need here is
>>>
>>> 	if (intel_state->dsi_self_refresh)
>>> 		val |= PIPECONF_MIPI_DSR_ENABLE;
>>>
>>> Also is that additional write really required?
>>> -Daniel
>> Yes additional write is required. MIPI_DSR_ENABLE has to be written first
>> then followed
>> by pipe enable. if MIPI_DSR_ENABLE and pipe enable is done in same write,
>> observed
>> that the image from pipe is not sent to panel when issued mem write command.
>>
>> Having a state variable instead of looping through the encoders definitely
>> looks good.
>> Need to find a place to update the state variable. I will get back on this.
> Like I said such state is precomputed in the encoder callbacks, in this
> case intel_dsi_compute_config.
>
> Cheers, Daniel
Agree with you daniel regarding state flag. Updated patch is ready, will 
upload shortly.

Regarding additional write, as Yogesh confirmed, both the writes are 
required.

With regards,
Gaurav
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