Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: > Quoting Sagar Arun Kamble (2018-04-20 11:23:50) >> >> >> On 4/20/2018 3:24 PM, Mika Kuoppala wrote: >> > We use jiffies to determine when wait expires. However >> > Imre did find out that jiffies can and will do a >1 >> > increments on certain situations [1]. When this happens >> > in a wait_for loop, we return timeout errorneously >> > much earlier than what the real wallclock would say. >> > >> > We can't afford our waits to timeout prematurely. >> > Discard jiffies and change to ktime to detect timeouts. >> > >> > Reported-by: Imre Deak <imre.deak@xxxxxxxxx> >> > References: https://lkml.org/lkml/2018/4/18/798 [1] >> > Cc: Imre Deak <imre.deak@xxxxxxxxx> >> > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> >> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >> > Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> >> > --- >> > drivers/gpu/drm/i915/intel_drv.h | 4 ++-- >> > 1 file changed, 2 insertions(+), 2 deletions(-) >> > >> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h >> > index 8b20824e806e..ac7565220aa3 100644 >> > --- a/drivers/gpu/drm/i915/intel_drv.h >> > +++ b/drivers/gpu/drm/i915/intel_drv.h >> > @@ -49,12 +49,12 @@ >> > * check the condition before the timeout. >> > */ >> > #define __wait_for(OP, COND, US, Wmin, Wmax) ({ \ >> > - unsigned long timeout__ = jiffies + usecs_to_jiffies(US) + 1; \ >> > + const ktime_t end__ = ktime_add_ns(ktime_get_raw(), 1000ll * (US)); \ >> Is ktime_get_raw() monotonic? Thomas suggested ktime_get() > > It proclaims to be monotonic, without the clock drift calibration. For > the milliseconds we should be sleeping at most, I hope that is > immaterial. Agreed. And even if we would be affected by drift, we would want to extend the end a little instead of accepting a drift calibration while we are waiting. Here is how the code size is affected: add/remove: 0/0 grow/shrink: 5/29 up/down: 77/-1099 (-1022) Function old new delta __intel_wait_for_register_fw 462 496 +34 swsci 576 596 +20 skl_pcode_request 488 507 +19 intel_hdcp_auth 3806 3809 +3 __intel_wait_for_register 436 437 +1 hsw_power_well_disable 548 539 -9 i915_gem_idle_work_handler 608 593 -15 guc_fw_xfer 875 854 -21 bxt_ddi_pll_disable 324 303 -21 chv_set_cdclk 357 334 -23 vlv_wm_get_hw_state 2474 2450 -24 gmbus_wait 564 538 -26 cnl_cdclk_pll_enable 286 259 -27 cnl_cdclk_pll_disable 247 220 -27 hsw_enable_pc8 1699 1671 -28 bdw_set_cdclk 1006 977 -29 wait_for_pipe_scanline_moving 388 358 -30 intel_enable_dsi_pll 1060 1028 -32 i915_gem_wait_for_idle 348 314 -34 chv_set_memory_dvfs 258 223 -35 vlv_set_power_well 321 282 -39 intel_hdmi_hdcp_check_link 485 446 -39 chv_set_pipe_power_well.constprop 359 320 -39 g33_do_reset 216 175 -41 vlv_wait_for_pw_status 210 168 -42 intel_engines_park 348 306 -42 vlv_set_cdclk 711 662 -49 lspcon_wait_mode 265 211 -54 lpt_init_pch_refclk 1542 1488 -54 g4x_do_reset 595 541 -54 bxt_ddi_pll_enable 2407 2353 -54 ironlake_crtc_enable 3279 3211 -68 i915_do_reset 443 375 -68 intel_guc_send_ct 1691 1616 -75 Total: Before=1232834, After=1231812, chg -0.08% -Mika _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
