Re: [PATCH v5 09/13] drm/i915/icl: Program TA_TIMING_PARAM registers

[Madhav Chauhan <madhav.chauhan@intel.com>]

On 9/12/2018 12:56 AM, Jani Nikula wrote:
> On Fri, 20 Jul 2018, "Chauhan, Madhav" <madhav.chauhan@intel.com> wrote:
>>> -----Original Message-----
>>> From: Ville Syrjälä [mailto:ville.syrjala@linux.intel.com]
>>> Sent: Thursday, July 19, 2018 9:51 PM
>>> To: Chauhan, Madhav <madhav.chauhan@intel.com>
>>> Cc: intel-gfx@lists.freedesktop.org; Nikula, Jani <jani.nikula@intel.com>;
>>> Zanoni, Paulo R <paulo.r.zanoni@intel.com>; Vivi, Rodrigo
>>> <rodrigo.vivi@intel.com>
>>> Subject: Re: [Intel-gfx] [PATCH v5 09/13] drm/i915/icl: Program
>>> TA_TIMING_PARAM registers
>>>
>>> On Tue, Jul 10, 2018 at 03:10:10PM +0530, Madhav Chauhan wrote:
>>>> This patch programs D-PHY timing parameters for the bus turn around
>>>> flow(in escape clocks) only if dsi link frequency <=800 MHz using
>>>> DPHY_TA_TIMING_PARAM and its identical register
>>> DSI_TA_TIMING_PARAM
>>>> (inside DSI Controller within the Display Core).
>>>>
>>>> Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
>>>> ---
>>>>   drivers/gpu/drm/i915/icl_dsi.c       | 21 +++++++++++++++++++++
>>>>   drivers/gpu/drm/i915/intel_dsi.h     |  1 +
>>>>   drivers/gpu/drm/i915/intel_dsi_vbt.c |  1 +
>>>>   3 files changed, 23 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/icl_dsi.c
>>>> b/drivers/gpu/drm/i915/icl_dsi.c index 832772d..8fd5284 100644
>>>> --- a/drivers/gpu/drm/i915/icl_dsi.c
>>>> +++ b/drivers/gpu/drm/i915/icl_dsi.c
>>>> @@ -302,6 +302,27 @@ static void gen11_dsi_setup_dphy_timings(struct
>>> intel_encoder *encoder)
>>>>   		I915_WRITE(DSI_DATA_TIMING_PARAM(port),
>>>>   			   intel_dsi->dphy_data_lane_reg);
>>>>   	}
>>>> +
>>>> +	/*
>>>> +	 * If DSI link operating at or below an 800 MHz,
>>>> +	 * TA_SURE should be override and programmed to
>>>> +	 * a value '0' inside TA_PARAM_REGISTERS otherwise
>>>> +	 * leave all fields at HW default values.
>>>> +	 */
>>>> +	if (intel_dsi->bitrate_khz <= KHz(800)) {
>>> The KHz(800) confuses me. My brain thinks this value is 800 kHz when it's
>>> not. So I'd write it without the KHz() macro.
>> Ok. Initially I wrote without using KHz macro, but got comment to use KHz macro :)
> Did I? Oh well. Go with 800000.

Ok  :)

>
> Please don't add additional state with intel_dsi->bitrate_khz when you
> can calculate the bitrate at any time. Add a function to do it if you
> like, and use it in both places.

Ok. But we will reusing this bitrate(same value) in multiple place. 
Shouldn't
we cache it rather than calculating everytime??

Regards,
Madhav

>
> BR,
> Jani.
>
>
>> Regards,
>> Madhav
>>
>>>> +		for_each_dsi_port(port, intel_dsi->ports) {
>>>> +			tmp = I915_READ(DPHY_TA_TIMING_PARAM(port));
>>>> +			tmp &= ~TA_SURE_TIME_MASK;
>>>> +			tmp |= (TA_SURE_OVERRIDE | TA_SURE_TIME(0));
>>>> +			I915_WRITE(DPHY_TA_TIMING_PARAM(port), tmp);
>>>> +
>>>> +			/* shadow register inside display core */
>>>> +			tmp = I915_READ(DSI_TA_TIMING_PARAM(port));
>>>> +			tmp &= ~TA_SURE_TIME_MASK;
>>>> +			tmp |= (TA_SURE_OVERRIDE | TA_SURE_TIME(0));
>>>> +			I915_WRITE(DSI_TA_TIMING_PARAM(port), tmp);
>>>> +		}
>>>> +	}
>>>>   }
>>>>
>>>>   static void gen11_dsi_enable_port_and_phy(struct intel_encoder
>>>> *encoder) diff --git a/drivers/gpu/drm/i915/intel_dsi.h
>>>> b/drivers/gpu/drm/i915/intel_dsi.h
>>>> index 9fd8526..25e7396 100644
>>>> --- a/drivers/gpu/drm/i915/intel_dsi.h
>>>> +++ b/drivers/gpu/drm/i915/intel_dsi.h
>>>> @@ -101,6 +101,7 @@ struct intel_dsi {
>>>>
>>>>   	u16 init_count;
>>>>   	u32 pclk;
>>>> +	u32 bitrate_khz;
>>>>   	u16 burst_mode_ratio;
>>>>
>>>>   	/* all delays in ms */
>>>> diff --git a/drivers/gpu/drm/i915/intel_dsi_vbt.c
>>>> b/drivers/gpu/drm/i915/intel_dsi_vbt.c
>>>> index 428290d..a9a98a4 100644
>>>> --- a/drivers/gpu/drm/i915/intel_dsi_vbt.c
>>>> +++ b/drivers/gpu/drm/i915/intel_dsi_vbt.c
>>>> @@ -589,6 +589,7 @@ bool intel_dsi_vbt_init(struct intel_dsi *intel_dsi,
>>> u16 panel_id)
>>>>   	intel_dsi->pclk = pclk;
>>>>
>>>>   	bitrate = (pclk * bpp) / intel_dsi->lane_count;
>>>> +	intel_dsi->bitrate_khz = bitrate;
>>>>
>>>>   	switch (intel_dsi->escape_clk_div) {
>>>>   	case 0:
>>>> --
>>>> 2.7.4
>>>>
>>>> _______________________________________________
>>>> Intel-gfx mailing list
>>>> Intel-gfx@lists.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>> --
>>> Ville Syrjälä
>>> Intel

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