From 2c7d0602c815277f7cb7c932b091288710d8aba7 Mon Sep 17 00:00:00 2001 From: Imre Deak Date: Mon, 5 Dec 2016 18:27:37 +0200 Subject: drm/i915/gen9: Fix PCODE polling during CDCLK change notification MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 848496e5902833600f7992f4faa82dc1546051ba Author: Ville Syrjälä Date: Wed Jul 13 16:32:03 2016 +0300 drm/i915: Wait up to 3ms for the pcu to ack the cdclk change request on SKL increased the timeout to match the spec, but we still see a timeout on at least one SKL. A CDCLK change request following the failed one will succeed nevertheless. I could reproduce this problem easily by running kms_pipe_crc_basic in a loop. In all failure cases _wait_for() was pre-empted for >3ms and so in the worst case - when the pre-emption happened right after calculating timeout__ in _wait_for() - we called skl_cdclk_wait_for_pcu_ready() only once which failed and so _wait_for() timed out. As opposed to this the spec says to keep retrying the request for at most a 3ms period. To fix this send the first request explicitly to guarantee that there is 3ms between the first and last request. Though this matches the spec, I noticed that in rare cases this can still time out if we sent only a few requests (in the worst case 2) _and_ PCODE is busy for some reason even after a previous request and a 3ms delay. To work around this retry the polling with pre-emption disabled to maximize the number of requests. Also increase the timeout to 10ms to account for interrupts that could reduce the number of requests. With this change I couldn't trigger the problem. v2: - Use 1ms poll period instead of 10us. (Chris) v3: - Poll with pre-emption disabled to increase the number of request attempts. (Ville, Chris) - Factor out a helper to poll, it's also needed by the next patch. v4: - Pass reply_mask, reply to skl_pcode_request(), instead of assuming the reply is generic. (Ville) v5: - List the request specific timeout values as code comment. (Ville) v6: - Try the poll first with preemption enabled. - Add code comment about first request being queued by PCODE. (Art) - Add timeout_base_ms argument. (Ville) v7: - Clarify code comment about first queued request. (Chris) Cc: Ville Syrjälä Cc: Chris Wilson Cc: Art Runyan Cc: # v4.2- : 3b2c171 : drm/i915: Wait up to 3ms Cc: # v4.2- Fixes: 5d96d8afcfbb ("drm/i915/skl: Deinit/init the display at suspend/resume") Reference: https://bugs.freedesktop.org/show_bug.cgi?id=97929 Testcase: igt/kms_pipe_crc_basic/suspend-read-crc-pipe-B Signed-off-by: Imre Deak Reviewed-by: Chris Wilson Link: http://patchwork.freedesktop.org/patch/msgid/1480955258-26311-1-git-send-email-imre.deak@intel.com (cherry picked from commit a0b8a1fe34430c3a82258e8cb45f5968bdf31afd) Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/intel_display.c | 31 ++++++++++--------------------- 1 file changed, 10 insertions(+), 21 deletions(-) (limited to 'drivers/gpu/drm/i915/intel_display.c') diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 4ef5a39acc69..7d234043822d 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -6244,35 +6244,24 @@ skl_dpll0_disable(struct drm_i915_private *dev_priv) dev_priv->cdclk_pll.vco = 0; } -static bool skl_cdclk_pcu_ready(struct drm_i915_private *dev_priv) -{ - int ret; - u32 val; - - /* inform PCU we want to change CDCLK */ - val = SKL_CDCLK_PREPARE_FOR_CHANGE; - mutex_lock(&dev_priv->rps.hw_lock); - ret = sandybridge_pcode_read(dev_priv, SKL_PCODE_CDCLK_CONTROL, &val); - mutex_unlock(&dev_priv->rps.hw_lock); - - return ret == 0 && (val & SKL_CDCLK_READY_FOR_CHANGE); -} - -static bool skl_cdclk_wait_for_pcu_ready(struct drm_i915_private *dev_priv) -{ - return _wait_for(skl_cdclk_pcu_ready(dev_priv), 3000, 10) == 0; -} - static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk, int vco) { u32 freq_select, pcu_ack; + int ret; WARN_ON((cdclk == 24000) != (vco == 0)); DRM_DEBUG_DRIVER("Changing CDCLK to %d kHz (VCO %d kHz)\n", cdclk, vco); - if (!skl_cdclk_wait_for_pcu_ready(dev_priv)) { - DRM_ERROR("failed to inform PCU about cdclk change\n"); + mutex_lock(&dev_priv->rps.hw_lock); + ret = skl_pcode_request(dev_priv, SKL_PCODE_CDCLK_CONTROL, + SKL_CDCLK_PREPARE_FOR_CHANGE, + SKL_CDCLK_READY_FOR_CHANGE, + SKL_CDCLK_READY_FOR_CHANGE, 3); + mutex_unlock(&dev_priv->rps.hw_lock); + if (ret) { + DRM_ERROR("Failed to inform PCU about cdclk change (%d)\n", + ret); return; } -- cgit v1.2.3