From 2c7d0602c815277f7cb7c932b091288710d8aba7 Mon Sep 17 00:00:00 2001 From: Imre Deak Date: Mon, 5 Dec 2016 18:27:37 +0200 Subject: [PATCH] drm/i915/gen9: Fix PCODE polling during CDCLK change notification MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 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/i915_drv.h | 2 + drivers/gpu/drm/i915/intel_display.c | 31 ++++-------- drivers/gpu/drm/i915/intel_pm.c | 75 ++++++++++++++++++++++++++++ 3 files changed, 87 insertions(+), 21 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 56002a52936d..243224aeabf8 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -3509,6 +3509,8 @@ extern void intel_display_print_error_state(struct drm_i915_error_state_buf *e, int sandybridge_pcode_read(struct drm_i915_private *dev_priv, u32 mbox, u32 *val); int sandybridge_pcode_write(struct drm_i915_private *dev_priv, u32 mbox, u32 val); +int skl_pcode_request(struct drm_i915_private *dev_priv, u32 mbox, u32 request, + u32 reply_mask, u32 reply, int timeout_base_ms); /* intel_sideband.c */ u32 vlv_punit_read(struct drm_i915_private *dev_priv, u32 addr); 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; } diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c index cbd0f3269b2d..90e42e094b13 100644 --- a/drivers/gpu/drm/i915/intel_pm.c +++ b/drivers/gpu/drm/i915/intel_pm.c @@ -7890,6 +7890,81 @@ int sandybridge_pcode_write(struct drm_i915_private *dev_priv, return 0; } +static bool skl_pcode_try_request(struct drm_i915_private *dev_priv, u32 mbox, + u32 request, u32 reply_mask, u32 reply, + u32 *status) +{ + u32 val = request; + + *status = sandybridge_pcode_read(dev_priv, mbox, &val); + + return *status || ((val & reply_mask) == reply); +} + +/** + * skl_pcode_request - send PCODE request until acknowledgment + * @dev_priv: device private + * @mbox: PCODE mailbox ID the request is targeted for + * @request: request ID + * @reply_mask: mask used to check for request acknowledgment + * @reply: value used to check for request acknowledgment + * @timeout_base_ms: timeout for polling with preemption enabled + * + * Keep resending the @request to @mbox until PCODE acknowledges it, PCODE + * reports an error or an overall timeout of @timeout_base_ms+10 ms expires. + * The request is acknowledged once the PCODE reply dword equals @reply after + * applying @reply_mask. Polling is first attempted with preemption enabled + * for @timeout_base_ms and if this times out for another 10 ms with + * preemption disabled. + * + * Returns 0 on success, %-ETIMEDOUT in case of a timeout, <0 in case of some + * other error as reported by PCODE. + */ +int skl_pcode_request(struct drm_i915_private *dev_priv, u32 mbox, u32 request, + u32 reply_mask, u32 reply, int timeout_base_ms) +{ + u32 status; + int ret; + + WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock)); + +#define COND skl_pcode_try_request(dev_priv, mbox, request, reply_mask, reply, \ + &status) + + /* + * Prime the PCODE by doing a request first. Normally it guarantees + * that a subsequent request, at most @timeout_base_ms later, succeeds. + * _wait_for() doesn't guarantee when its passed condition is evaluated + * first, so send the first request explicitly. + */ + if (COND) { + ret = 0; + goto out; + } + ret = _wait_for(COND, timeout_base_ms * 1000, 10); + if (!ret) + goto out; + + /* + * The above can time out if the number of requests was low (2 in the + * worst case) _and_ PCODE was busy for some reason even after a + * (queued) request and @timeout_base_ms delay. As a workaround retry + * the poll with preemption disabled to maximize the number of + * requests. Increase the timeout from @timeout_base_ms to 10ms to + * account for interrupts that could reduce the number of these + * requests. + */ + DRM_DEBUG_KMS("PCODE timeout, retrying with preemption disabled\n"); + WARN_ON_ONCE(timeout_base_ms > 3); + preempt_disable(); + ret = wait_for_atomic(COND, 10); + preempt_enable(); + +out: + return ret ? ret : status; +#undef COND +} + static int byt_gpu_freq(struct drm_i915_private *dev_priv, int val) { /* -- 2.30.2