On ma, 2016-11-28 at 17:58 +0200, Ville Syrjälä wrote: > On Mon, Nov 28, 2016 at 05:29:28PM +0200, Imre Deak wrote: > > commit 848496e5902833600f7992f4faa82dc1546051ba > > Author: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > 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 disable pre-emption to maximize the number of times we retry > > the request. Also increase the timeout to 10ms to account for interrupts > > that could reduce the number of these attempts. 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) > > > > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > 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 <imre.deak@xxxxxxxxx> > > --- > > drivers/gpu/drm/i915/i915_drv.h | 2 ++ > > drivers/gpu/drm/i915/intel_display.c | 31 ++++++++--------------- > > drivers/gpu/drm/i915/intel_pm.c | 49 ++++++++++++++++++++++++++++++++++++ > > 3 files changed, 61 insertions(+), 21 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > > index 01f5067..1be5bab 100644 > > --- a/drivers/gpu/drm/i915/i915_drv.h > > +++ b/drivers/gpu/drm/i915/i915_drv.h > > @@ -3593,6 +3593,8 @@ 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); > > > > /* 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 5d11002..3d220da 100644 > > --- a/drivers/gpu/drm/i915/intel_display.c > > +++ b/drivers/gpu/drm/i915/intel_display.c > > @@ -6245,35 +6245,24 @@ 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); > > + 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 66c62f3..aed88e0 100644 > > --- a/drivers/gpu/drm/i915/intel_pm.c > > +++ b/drivers/gpu/drm/i915/intel_pm.c > > @@ -7864,6 +7864,55 @@ 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 acknowledgement > > + * > > + * Keep resending the @request to @mbox until PCODE acknowledges it, PCODE > > + * reports an error or a 10ms timeout expires. The request is acknowledged > > + * once the PCODE reply dword equals @reply after aplying @reply_mask. > > + * > > + * 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) > > +{ > > + u32 status; > > + int ret; > > + > > + WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock)); > > + > > + /* > > + * The spec says to keep retrying the request for at most 3ms until > > This comment seems a little misplaced. The 3ms is specified for the > cdclk prep request, SAGV will have a different value. > If we don't want callers to pass in the timeout as well, I guess we'll > at least want to reword this comment to say which callers need what > kind of timeouts. How about "at most 3ms - which can be less depending on the given request"? > Though I kinda like the idea of callers passing that > in as well. The 10ms timeout I chose here is anyway an upper bound, considering that interrupts could reduce the number of requests we can send. Hence thought to make it a generic value. > > > + * acknowledgement, so disable pre-emption to maximize the number of > > + * attempts within this duration. Use a 10ms overall timeout to > > + * account for interrupts that could reduce the number of attempts. > > + */ > > + preempt_disable(); > > + ret = wait_for_atomic(skl_pcode_try_request(dev_priv, mbox, request, > > + reply_mask, reply, &status), > > + 10); > > + preempt_enable(); > > + > > + return ret ? ret : status; > > +} > > + > > static int byt_gpu_freq(struct drm_i915_private *dev_priv, int val) > > { > > /* > > -- > > 2.5.0 > _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
