Thanks Imre for the explanation.
I will repost the patch..
Regards,
Sonika
-----Original Message-----
From: Deak, Imre
Sent: Wednesday, September 23, 2015 5:15 PM
To: Jindal, Sonika
Cc: Thulasimani, Sivakumar; intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Ville Syrjälä
Subject: Re: [PATCH 1/2] drm/i915/bxt: Set oscaledcompmethod to enable scale value
On ke, 2015-09-23 at 09:37 +0530, Jindal, Sonika wrote:
>
> On 9/23/2015 1:02 AM, Imre Deak wrote:
> > On Wed, 2015-09-23 at 00:01 +0530, Sivakumar Thulasimani wrote:
> >>
> >> On 9/22/2015 6:32 PM, Imre Deak wrote:
> >>> On ma, 2015-09-21 at 23:00 +0530, Sivakumar Thulasimani wrote:
> >>>> Reviewed-by: Sivakumar Thulasimani
> >>>> <sivakumar.thulasimani@xxxxxxxxx>
> >>>>
> >>>> 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@xxxxxxxxx>
> >>>>> ---
> >>>>> 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.
> >>>
> Now it doesn't make a difference after we have set the
> oscalecompmethod correctly. But when we were not doing that, this
> 'don't care' value was making a difference. It was being considered.
> I am sure of this because with low vswing table, only when I added
> 0x9A, it worked for me because we were not unsetting the oscaledcompmenthod.
Yes, that's expected. BIOS has set oscaledcompmethod and the driver didn't change it, so it remained set. With that bit set the scale value does matter, so setting the scale value to zero (or some other low
value) will definitely not work.
> So, I think its better to reset it to some value other than 0x9A.
It wouldn't make sense based on the updated Bspec and test results. It would also be different from what we do for HDMI and CHV (which has the same PHY) again without any explanation.
> Regarding 0x98 being the reset value, is it mentioned in bspec?
You can check this by reading out the register right after toggling the relevant power well. Bspec doesn't seem to provide the reset values for any of the PHY registers.
> I couldn't find that in the table. If that is the case, we can make it
> 0x98 instead of 0x9A.
I wouldn't change these values for now. If in the future testing shows that these values matter even if both oscaledcompmethod and ouniqetrangenmethod is clear, we could change them in a separate patch explaining the reason for the change, considering also HDMI and other platforms (CHV). Also we should then get an explanation from the HW people why things don't work according to the specification.
> >>>>> { 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.
> >>>
> Again, I couldn't find it mentioned anywhere that scaling value
> depends on "ouniqetrangenmethod" ? Is it in bspec?
This can be seen just by setting ouniqetrangenmethod and leaving oscaledcompmethod clear. Setting a low scale value in this case will result in no valid signal and blank screen.
> Although it does seem to make a difference in case of low vswing table.
> With default table, it edp continues to work if set or not set this bit.
> I will add back the unsetting of this bit and then setting of this bit
> when 'enable' is set.
According to Bspec we should do an RMW on this register and don't change ouniqetrangenmethod. So I wouldn't set or clear it, but have the check and DRM_ERROR in case BIOS has set it for some reason (maybe old/buggy
BIOS) which could help understanding if things don't work.
--Imre
> Regards,
> Sonik
> >> This was the only place UNIQE_TRANGE_EN_METHOD was set before, with
> >> that removed only possibility for it to be set is by GOP/VBIOS.
> >> (who are also expected to make this change if not done already.) in
> >> such a scenario wont an error message be useless here ?
> >
> > Yes, this is exactly a check for BIOS settings. It wouldn't be the
> > first case that BIOS didn't program something according to our
> > expectations, especially given the multiple versions out there.
> >
> >>>>> I915_WRITE(BXT_PORT_TX_DW3_GRP(port), val);
> >>>>>
> >>>>> val = I915_READ(BXT_PORT_TX_DW4_LN0(port));
> >>>
> >>>
> >>>
> >>
> >>
> >
> >
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