Re: [PATCH 45/62] drm/i915/bdw: add support for BDW DP voltage swings and pre-emphasis

Ben Widawsky
2013-11-05T00:45:16Z

On Sat, Nov 02, 2013 at 09:07:43PM -0700, Ben Widawsky wrote:
> From: Paulo Zanoni <paulo.r.zanoni@intel.com>
>
> They're not the same as the Haswell ones.
>
> Reviewed-by: Art Runyan <arthur.j.runyan@intel.com>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> ---
> drivers/gpu/drm/i915/i915_reg.h | 11 +++++++++
> drivers/gpu/drm/i915/intel_dp.c | 55 ++++++++++++++++++++++++++++++++++++++---
> 2 files changed, 63 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 4131223..6f834b3 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -5176,6 +5176,7 @@
> #define DDI_BUF_CTL_B 0x64100
> #define DDI_BUF_CTL(port) _PORT(port, DDI_BUF_CTL_A, DDI_BUF_CTL_B)
> #define DDI_BUF_CTL_ENABLE (1<<31)
> +/* Haswell */
> #define DDI_BUF_EMP_400MV_0DB_HSW (0<<24) /* Sel0 */
> #define DDI_BUF_EMP_400MV_3_5DB_HSW (1<<24) /* Sel1 */
> #define DDI_BUF_EMP_400MV_6DB_HSW (2<<24) /* Sel2 */
> @@ -5185,6 +5186,16 @@
> #define DDI_BUF_EMP_600MV_6DB_HSW (6<<24) /* Sel6 */
> #define DDI_BUF_EMP_800MV_0DB_HSW (7<<24) /* Sel7 */
> #define DDI_BUF_EMP_800MV_3_5DB_HSW (8<<24) /* Sel8 */
> +/* Broadwell */
> +#define DDI_BUF_EMP_400MV_0DB_BDW (0<<24) /* Sel0 */
> +#define DDI_BUF_EMP_400MV_3_5DB_BDW (1<<24) /* Sel1 */
> +#define DDI_BUF_EMP_400MV_6DB_BDW (2<<24) /* Sel2 */
> +#define DDI_BUF_EMP_600MV_0DB_BDW (3<<24) /* Sel3 */
> +#define DDI_BUF_EMP_600MV_3_5DB_BDW (4<<24) /* Sel4 */
> +#define DDI_BUF_EMP_600MV_6DB_BDW (5<<24) /* Sel5 */

Maybe I am misreading this, isn't this:
600mV, 4.5dB?

> +#define DDI_BUF_EMP_800MV_0DB_BDW (6<<24) /* Sel6 */

850, .5

> +#define DDI_BUF_EMP_800MV_3_5DB_BDW (7<<24) /* Sel7 */

750, 2.5

> +#define DDI_BUF_EMP_1200MV_0DB_BDW (8<<24) /* Sel8 */

1000, 0

Sorry if I just misunderstood how you're getting these values.

> #define DDI_BUF_EMP_MASK (0xf<<24)
> #define DDI_BUF_PORT_REVERSAL (1<<16)
> #define DDI_BUF_IS_IDLE (1<<7)
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index b3cc333..7725f81 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1950,7 +1950,7 @@ intel_dp_voltage_max(struct intel_dp *intel_dp)
> struct drm_device *dev = intel_dp_to_dev(intel_dp);
> enum port port = dp_to_dig_port(intel_dp)->port;
>
> - if (IS_VALLEYVIEW(dev))
> + if (IS_VALLEYVIEW(dev) || IS_BROADWELL(dev))
> return DP_TRAIN_VOLTAGE_SWING_1200;
> else if (IS_GEN7(dev) && port == PORT_A)
> return DP_TRAIN_VOLTAGE_SWING_800;
> @@ -1966,7 +1966,18 @@ intel_dp_pre_emphasis_max(struct intel_dp *intel_dp, uint8_t voltage_swing)
> struct drm_device *dev = intel_dp_to_dev(intel_dp);
> enum port port = dp_to_dig_port(intel_dp)->port;
>
> - if (HAS_DDI(dev)) {
> + if (IS_BROADWELL(dev)) {
> + switch (voltage_swing & DP_TRAIN_VOLTAGE_SWING_MASK) {
> + case DP_TRAIN_VOLTAGE_SWING_400:
> + case DP_TRAIN_VOLTAGE_SWING_600:
> + return DP_TRAIN_PRE_EMPHASIS_6;
> + case DP_TRAIN_VOLTAGE_SWING_800:
> + return DP_TRAIN_PRE_EMPHASIS_3_5;
> + case DP_TRAIN_VOLTAGE_SWING_1200:
> + default:
> + return DP_TRAIN_PRE_EMPHASIS_0;
> + }
> + } else if (IS_HASWELL(dev)) {
> switch (voltage_swing & DP_TRAIN_VOLTAGE_SWING_MASK) {
> case DP_TRAIN_VOLTAGE_SWING_400:
> return DP_TRAIN_PRE_EMPHASIS_9_5;
> @@ -2278,6 +2289,41 @@ intel_hsw_signal_levels(uint8_t train_set)
> }
> }
>
> +static uint32_t
> +intel_bdw_signal_levels(uint8_t train_set)
> +{
> + int signal_levels = train_set & (DP_TRAIN_VOLTAGE_SWING_MASK |
> + DP_TRAIN_PRE_EMPHASIS_MASK);
> + switch (signal_levels) {
> + case DP_TRAIN_VOLTAGE_SWING_400 | DP_TRAIN_PRE_EMPHASIS_0:
> + return DDI_BUF_EMP_400MV_0DB_BDW; /* Sel0 */
> + case DP_TRAIN_VOLTAGE_SWING_400 | DP_TRAIN_PRE_EMPHASIS_3_5:
> + return DDI_BUF_EMP_400MV_3_5DB_BDW; /* Sel1 */
> + case DP_TRAIN_VOLTAGE_SWING_400 | DP_TRAIN_PRE_EMPHASIS_6:
> + return DDI_BUF_EMP_400MV_6DB_BDW; /* Sel2 */
> +
> + case DP_TRAIN_VOLTAGE_SWING_600 | DP_TRAIN_PRE_EMPHASIS_0:
> + return DDI_BUF_EMP_600MV_0DB_BDW; /* Sel3 */
> + case DP_TRAIN_VOLTAGE_SWING_600 | DP_TRAIN_PRE_EMPHASIS_3_5:
> + return DDI_BUF_EMP_600MV_3_5DB_BDW; /* Sel4 */
> + case DP_TRAIN_VOLTAGE_SWING_600 | DP_TRAIN_PRE_EMPHASIS_6:
> + return DDI_BUF_EMP_600MV_6DB_BDW; /* Sel5 */
> +
> + case DP_TRAIN_VOLTAGE_SWING_800 | DP_TRAIN_PRE_EMPHASIS_0:
> + return DDI_BUF_EMP_800MV_0DB_BDW; /* Sel6 */
> + case DP_TRAIN_VOLTAGE_SWING_800 | DP_TRAIN_PRE_EMPHASIS_3_5:
> + return DDI_BUF_EMP_800MV_3_5DB_BDW; /* Sel7 */
> +
> + case DP_TRAIN_VOLTAGE_SWING_1200 | DP_TRAIN_PRE_EMPHASIS_0:
> + return DDI_BUF_EMP_1200MV_0DB_BDW; /* Sel8 */
> +
> + default:
> + DRM_DEBUG_KMS("Unsupported voltage swing/pre-emphasis level:"
> + "0x%x\n", signal_levels);
> + return DDI_BUF_EMP_400MV_0DB_BDW; /* Sel0 */
> + }
> +}
> +
> /* Properly updates "DP" with the correct signal levels. */
> static void
> intel_dp_set_signal_levels(struct intel_dp *intel_dp, uint32_t *DP)
> @@ -2288,7 +2334,10 @@ intel_dp_set_signal_levels(struct intel_dp *intel_dp, uint32_t *DP)
> uint32_t signal_levels, mask;
> uint8_t train_set = intel_dp->train_set[0];
>
> - if (HAS_DDI(dev)) {
> + if (IS_BROADWELL(dev)) {
> + signal_levels = intel_bdw_signal_levels(train_set);
> + mask = DDI_BUF_EMP_MASK;
> + } else if (IS_HASWELL(dev)) {
> signal_levels = intel_hsw_signal_levels(train_set);
> mask = DDI_BUF_EMP_MASK;
> } else if (IS_VALLEYVIEW(dev)) {

Forgive my ignorance, but I really have no idea how to review this
patch. Daniel, I think we have to settle for Art's r-b on this one, or
finds someone who understands why this programming is the way it is. (Or
wait)

--
Ben Widawsky, Intel Open Source Technology Center