[PATCH 3.16 194/305] drm/i915/ilk: Don't disable SSC source if it's in use

Ben Hutchings
2016-08-14T11:33:07Z

From: Lyude <cpaul@redhat.com>

commit 476490a945e1f0f6bd58e303058d2d8ca93a974c upstream.

Thanks to Ville Syrjälä for pointing me towards the cause of this issue.

Unfortunately one of the sideaffects of having the refclk for a DPLL set
to SSC is that as long as it's set to SSC, the GPU will prevent us from
powering down any of the pipes or transcoders using it. A couple of
BIOSes enable SSC in both PCH_DREF_CONTROL and in the DPLL
configurations. This causes issues on the first modeset, since we don't
expect SSC to be left on and as a result, can't successfully power down
the pipes or the transcoders using it. Here's an example from this Dell
OptiPlex 990:

[drm:intel_modeset_init] SSC enabled by BIOS, overriding VBT which says disabled
[drm:intel_modeset_init] 2 display pipes available.
[drm:intel_update_cdclk] Current CD clock rate: 400000 kHz
[drm:intel_update_max_cdclk] Max CD clock rate: 400000 kHz
[drm:intel_update_max_cdclk] Max dotclock rate: 360000 kHz
vgaarb: device changed decodes: PCI:0000:00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem
[drm:intel_crt_reset] crt adpa set to 0xf40000
[drm:intel_dp_init_connector] Adding DP connector on port C
[drm:intel_dp_aux_init] registering DPDDC-C bus for card0-DP-1
[drm:ironlake_init_pch_refclk] has_panel 0 has_lvds 0 has_ck505 0
[drm:ironlake_init_pch_refclk] Disabling SSC entirely
… later we try committing the first modeset …
[drm:intel_dump_pipe_config] [CRTC:26][modeset] config ffff88041b02e800 for pipe A
[drm:intel_dump_pipe_config] cpu_transcoder: A
…
[drm:intel_dump_pipe_config] dpll_hw_state: dpll: 0xc4016001, dpll_md: 0x0, fp0: 0x20e08, fp1: 0x30d07
[drm:intel_dump_pipe_config] planes on this crtc
[drm:intel_dump_pipe_config] STANDARD PLANE:23 plane: 0.0 idx: 0 enabled
[drm:intel_dump_pipe_config] FB:42, fb = 800x600 format = 0x34325258
[drm:intel_dump_pipe_config] scaler:0 src (0, 0) 800x600 dst (0, 0) 800x600
[drm:intel_dump_pipe_config] CURSOR PLANE:25 plane: 0.1 idx: 1 disabled, scaler_id = 0
[drm:intel_dump_pipe_config] STANDARD PLANE:27 plane: 0.1 idx: 2 disabled, scaler_id = 0
[drm:intel_get_shared_dpll] CRTC:26 allocated PCH DPLL A
[drm:intel_get_shared_dpll] using PCH DPLL A for pipe A
[drm:ilk_audio_codec_disable] Disable audio codec on port C, pipe A
[drm:intel_disable_pipe] disabling pipe A
------------[ cut here ]------------
WARNING: CPU: 1 PID: 130 at drivers/gpu/drm/i915/intel_display.c:1146 intel_disable_pipe+0x297/0x2d0 [i915]
pipe_off wait timed out
…
---[ end trace 94fc8aa03ae139e8 ]---
[drm:intel_dp_link_down]
[drm:ironlake_crtc_disable [i915]] *ERROR* failed to disable transcoder A

Later modesets succeed since they reset the DPLL's configuration anyway,
but this is enough to get stuck with a big fat warning in dmesg.

A better solution would be to add refcounts for the SSC source, but for
now leaving the source clock on should suffice.

Changes since v4:
- Fix calculation of final for systems with LVDS panels (fixes BUG() on
CI test suite)
Changes since v3:
- Move temp variable into loop
- Move checks for using_ssc_source to after we've figured out has_ck505
- Add using_ssc_source to debug output
Changes since v2:
- Fix debug output for when we disable the CPU source
Changes since v1:
- Leave the SSC source clock on instead of just shutting it off on all
of the DPLL configurations.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Lyude <cpaul@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1465916649-10228-1-git-send-email-cpaul@redhat.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/gpu/drm/i915/intel_display.c | 48 +++++++++++++++++++++++++-----------
1 file changed, 34 insertions(+), 14 deletions(-)

--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6263,12 +6263,14 @@ static void ironlake_init_pch_refclk(str
struct drm_i915_private *dev_priv = dev->dev_private;
struct drm_mode_config *mode_config = &dev->mode_config;
struct intel_encoder *encoder;
+ int i;
u32 val, final;
bool has_lvds = false;
bool has_cpu_edp = false;
bool has_panel = false;
bool has_ck505 = false;
bool can_ssc = false;
+ bool using_ssc_source = false;

/* We need to take the global config into account */
list_for_each_entry(encoder, &mode_config->encoder_list,
@@ -6294,8 +6296,22 @@ static void ironlake_init_pch_refclk(str
can_ssc = true;
}

- DRM_DEBUG_KMS("has_panel %d has_lvds %d has_ck505 %d\n",
- has_panel, has_lvds, has_ck505);
+ /* Check if any DPLLs are using the SSC source */
+ for (i = 0; i < dev_priv->num_shared_dpll; i++) {
+ u32 temp = I915_READ(PCH_DPLL(i));
+
+ if (!(temp & DPLL_VCO_ENABLE))
+ continue;
+
+ if ((temp & PLL_REF_INPUT_MASK) ==
+ PLLB_REF_INPUT_SPREADSPECTRUMIN) {
+ using_ssc_source = true;
+ break;
+ }
+ }
+
+ DRM_DEBUG_KMS("has_panel %d has_lvds %d has_ck505 %d using_ssc_source %d\n",
+ has_panel, has_lvds, has_ck505, using_ssc_source);

/* Ironlake: try to setup display ref clock before DPLL
* enabling. This is only under driver's control after
@@ -6332,9 +6348,9 @@ static void ironlake_init_pch_refclk(str
final |= DREF_CPU_SOURCE_OUTPUT_NONSPREAD;
} else
final |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
- } else {
- final |= DREF_SSC_SOURCE_DISABLE;
- final |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
+ } else if (using_ssc_source) {
+ final |= DREF_SSC_SOURCE_ENABLE;
+ final |= DREF_SSC1_ENABLE;
}

if (final == val)
@@ -6380,7 +6396,7 @@ static void ironlake_init_pch_refclk(str
POSTING_READ(PCH_DREF_CONTROL);
udelay(200);
} else {
- DRM_DEBUG_KMS("Disabling SSC entirely\n");
+ DRM_DEBUG_KMS("Disabling CPU source output\n");

val &= ~DREF_CPU_SOURCE_OUTPUT_MASK;

@@ -6391,16 +6407,20 @@ static void ironlake_init_pch_refclk(str
POSTING_READ(PCH_DREF_CONTROL);
udelay(200);

- /* Turn off the SSC source */
- val &= ~DREF_SSC_SOURCE_MASK;
- val |= DREF_SSC_SOURCE_DISABLE;
+ if (!using_ssc_source) {
+ DRM_DEBUG_KMS("Disabling SSC source\n");

- /* Turn off SSC1 */
- val &= ~DREF_SSC1_ENABLE;
+ /* Turn off the SSC source */
+ val &= ~DREF_SSC_SOURCE_MASK;
+ val |= DREF_SSC_SOURCE_DISABLE;

- I915_WRITE(PCH_DREF_CONTROL, val);
- POSTING_READ(PCH_DREF_CONTROL);
- udelay(200);
+ /* Turn off SSC1 */
+ val &= ~DREF_SSC1_ENABLE;
+
+ I915_WRITE(PCH_DREF_CONTROL, val);
+ POSTING_READ(PCH_DREF_CONTROL);
+ udelay(200);
+ }
}

BUG_ON(val != final);