Re: [PATCH 1/2] drm/i915/bxt: Set oscaledcompmethod to enable scale value

[Imre Deak <imre.deak@intel.com>]

On ma, 2015-09-21 at 23:00 +0530, Sivakumar Thulasimani wrote:
> Reviewed-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
> 
> On 9/18/2015 2:11 PM, Sonika Jindal wrote:
> > Bspec update tells that we have to enable oscaledcompmethod instead of
> > ouniqetrangenmethod for enabling scale value during swing programming.
> > Also, scale value is 'don't care' for other levels except the last entry
> > translation table. So, make it 0 instead of 0x9A.
> >
> > Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
> > ---
> >   drivers/gpu/drm/i915/i915_reg.h  |    2 +-
> >   drivers/gpu/drm/i915/intel_ddi.c |   22 +++++++++++-----------
> >   2 files changed, 12 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index 812b7b2..cec6546 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -1395,7 +1395,7 @@ enum skl_disp_power_wells {
> >   #define BXT_PORT_TX_DW3_LN0(port)	_PORT3(port, _PORT_TX_DW3_LN0_A,  \
> >   						     _PORT_TX_DW3_LN0_B,  \
> >   						     _PORT_TX_DW3_LN0_C)
> > -#define   UNIQE_TRANGE_EN_METHOD	(1 << 27)
> > +#define   SCALE_DCOMP_METHOD		(1 << 26)
> >   
> >   #define _PORT_TX_DW4_LN0_A		0x162510
> >   #define _PORT_TX_DW4_LN0_B		0x6C510
> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > index fec51df..0d9b304 100644
> > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > @@ -261,15 +261,15 @@ struct bxt_ddi_buf_trans {
> >    */
> >   static const struct bxt_ddi_buf_trans bxt_ddi_translations_dp[] = {
> >   					/* Idx	NT mV diff	db  */
> > -	{ 52,  0x9A, 0, 128, true  },	/* 0:	400		0   */
> > -	{ 78,  0x9A, 0, 85,  false },	/* 1:	400		3.5 */
> > -	{ 104, 0x9A, 0, 64,  false },	/* 2:	400		6   */
> > -	{ 154, 0x9A, 0, 43,  false },	/* 3:	400		9.5 */
> > -	{ 77,  0x9A, 0, 128, false },	/* 4:	600		0   */
> > -	{ 116, 0x9A, 0, 85,  false },	/* 5:	600		3.5 */
> > -	{ 154, 0x9A, 0, 64,  false },	/* 6:	600		6   */
> > -	{ 102, 0x9A, 0, 128, false },	/* 7:	800		0   */
> > -	{ 154, 0x9A, 0, 85,  false },	/* 8:	800		3.5 */
> > +	{ 52,  0, 0, 128, true  },	/* 0:	400		0   */
> > +	{ 78,  0, 0, 85,  false },	/* 1:	400		3.5 */
> > +	{ 104, 0, 0, 64,  false },	/* 2:	400		6   */
> > +	{ 154, 0, 0, 43,  false },	/* 3:	400		9.5 */
> > +	{ 77,  0, 0, 128, false },	/* 4:	600		0   */
> > +	{ 116, 0, 0, 85,  false },	/* 5:	600		3.5 */
> > +	{ 154, 0, 0, 64,  false },	/* 6:	600		6   */
> > +	{ 102, 0, 0, 128, false },	/* 7:	800		0   */
> > +	{ 154, 0, 0, 85,  false },	/* 8:	800		3.5 */

There is no point in changing the above values as they are don't-care in
any case. In fact the reset value is 0x98 so I'd program that for these
cases if we ever wanted to change them. For now I'd leave this as-is to
keep in sync with the bxt_ddi_translations_hdmi table and also what CHV
does.

> >   	{ 154, 0x9A, 1, 128, false },	/* 9:	1200		0   */
> >   };


> >   
> > @@ -2151,9 +2151,9 @@ static void bxt_ddi_vswing_sequence(struct drm_device *dev, u32 level,
> >   	I915_WRITE(BXT_PORT_TX_DW2_GRP(port), val);
> >   
> >   	val = I915_READ(BXT_PORT_TX_DW3_LN0(port));
> > -	val &= ~UNIQE_TRANGE_EN_METHOD;
> > +	val &= ~SCALE_DCOMP_METHOD;
> >   	if (ddi_translations[level].enable)
> > -		val |= UNIQE_TRANGE_EN_METHOD;
> > +		val |= SCALE_DCOMP_METHOD;

Please still leave behind a DRM_ERROR in case UNIQE_TRANGE_EN_METHOD was
set in the register and we are disabling scaling. The scaling value does
seem to depend on this bit too, so seeing if it was set can help
tracking down problems.

> >   	I915_WRITE(BXT_PORT_TX_DW3_GRP(port), val);
> >   
> >   	val = I915_READ(BXT_PORT_TX_DW4_LN0(port));
> 


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