Re: [PATCH v2 13/13] drm/i915: Acquire P-Unit access when modifying P-Unit settings

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 30-01-17 16:11, Ville Syrjälä wrote:
> On Mon, Jan 30, 2017 at 04:02:19PM +0100, Hans de Goede wrote:
>> Hi,
>>
>> On 30-01-17 14:10, Ville Syrjälä wrote:
>>> On Sat, Jan 28, 2017 at 06:18:45PM +0100, Hans de Goede wrote:
>>>> Hi,
>>>>
>>>> On 01/28/2017 05:25 PM, Hans de Goede wrote:
>>>>> Hi,
>>>>>
>>>>> On 01/27/2017 02:51 PM, Ville Syrjälä wrote:
>>>>>> On Mon, Jan 23, 2017 at 10:09:58PM +0100, Hans de Goede wrote:
>>>>>>> Make sure the P-Unit or the PMIC i2c bus is not in use when we send a
>>>>>>> request to the P-Unit by calling iosf_mbi_punit_acquire() / _release()
>>>>>>> around P-Unit write accesses.
>>>>>>
>>>>>> Can't we just stuff the calls into the actual punit write function
>>>>>> rather than sprinkling them all over the place?
>>>>>
>>>>> punit access is acquired across sections like this:
>>>>>
>>>>>         iosf_mbi_punit_acquire();
>>>>>
>>>>>         val = vlv_punit_read(dev_priv, PUNIT_REG_DSPFREQ);
>>>>>         val &= ~DSPFREQGUAR_MASK;
>>>>>         val |= (cmd << DSPFREQGUAR_SHIFT);
>>>>>         vlv_punit_write(dev_priv, PUNIT_REG_DSPFREQ, val);
>>>>>         if (wait_for((vlv_punit_read(dev_priv, PUNIT_REG_DSPFREQ) &
>>>>>                       DSPFREQSTAT_MASK) == (cmd << DSPFREQSTAT_SHIFT),
>>>>>                      50)) {
>>>>>                 DRM_ERROR("timed out waiting for CDclk change\n");
>>>>>         }
>>>>>         iosf_mbi_punit_release();
>>>>>
>>>>> Where we want to wait for the requested change to have taken
>>>>> effect before releasing the punit.
>>>
>>> Hmm. That's somewhat unfortunate. It also highlights a problem with the
>>> patch wrt. RPS. We don't wait for the GPU to actually change frequencies
>>> in set_rps() because that would slow things down too much. So I have to
>>> wonder how much luck is needed to make this workaround really effective.
>>
>> So the history of this patch-set is that I wrote this patch before
>> writing the patch to get FORCEWAKE_ALL before the pmic bus becomes
>> active (patch 12/13). Since a lot of testing was done with this
>> patch included in the patch-set and since it seemed a good idea
>> regardless (given my experience with accessing the punit vs
>> pmic bus accesses) I decided to leave it in.
>>
>> Possibly just the patch to get FORCEWAKE_ALL is enough, that one
>> actually fixed things for me. That is also why I made this the
>> last patch in the set. I asked tagorereddy to test his system
>> without this patch, but he did not get around to that.
>>
>> After all we do tell the punit to not touch the bus by acquiring
>> the pmic bus semaphore from i2c-desigware-baytrail.c, so maybe
>> for RPS freq changes it honors that and properly waits. Maybe it
>> honors that for all punit requests i915 does and the only real
>> problem is the forcewake stuff ?
>>
>> I can try to drop this patch from my queue and run without it
>> for a while and see if things don't regress. And also ask
>> tagorereddy again to test his system that way.
>>
>> Does that (dropping this patch for now) sound like a good idea?
>
> More test results couldn't hurt at least. It also makes me wonder if
> just bumping the timeouts to some ridiculously high value would fix
> the problem as well.

I've already tried bumping the forcewake timeout from 50 to 250ms,
before writing the patch to just get forcewake_all before the pmic
bus access begins, that does not fix things, and since we busy wait
for this timeout from non-sleeping context 250ms already is way too
high.

>>>>>> + a comment would be nice why it's there.
>>>>>
>>>>> I will add comments to the acquire calls.
>>>>>
>>>>>> Do we need a kconfig select/depends on the iosf_mbi thing? Or some
>>>>>> ifdefs?
>>>>>
>>>>> No, the iosf_mbi header defines empty inline versions of
>>>>> iosf_mbi_punit_acquire / _release if IOSF_MBI is disabled,
>>>>> this does mean that iosf_mbi must be builtin if the i915
>>>>> driver is. I'll add:
>>>>>
>>>>>     depends on DRM_I915=IOSF_MBI || IOSF_MBI=y
>>>>>
>>>>> To the i915 Kconfig to enforce this.
>>>>
>>>> Hmm, ok so that does not work (long cyclic dependency through the
>>>> selection of ACPI_VIDEO).
>>>>
>>>> So I've now added this instead:
>>>>
>>>> 	# iosf_mbi needs to be builtin if we are builtin
>>>> 	select IOSF_MBI if DRM_I915=y
>>>
>>> That's probably not going to help anyone since i915 is usually a module.
>>
>> Right, that is fine, then either the IOSF_MBI symbols are available,
>> or IOSF_MBI is disabled and we get the inline nops from the header.
>>
>> The problem scenario is DRM_I915=y and IOSF_MBI=m, which is not very
>> realistic IMHO, but will get triggered by the random-config testing
>> several contributors do and lead to an unresolved symbol error there.
>
> Well, from the user POV anything with IOSF_MBI==n can be a problem.
> So I'm not sure if we should allow that.

So you're suggesting we just add an unconditional "select IOSF_MBI"
to the i915 Kconfig entry?

Regards,

Hans



>>>>>>> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=155241
>>>>>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>>>>>> Tested-by: tagorereddy <tagore.chandan@gmail.com>
>>>>>>> ---
>>>>>>> Changes in v2:
>>>>>>> -Spelling: P-Unit, PMIC
>>>>>>> -Adjust for iosf_mbi_punit_lock/_unlock to _acquire/_release rename
>>>>>>> ---
>>>>>>>  drivers/gpu/drm/i915/intel_display.c    | 6 ++++++
>>>>>>>  drivers/gpu/drm/i915/intel_pm.c         | 9 +++++++++
>>>>>>>  drivers/gpu/drm/i915/intel_runtime_pm.c | 9 +++++++++
>>>>>>>  3 files changed, 24 insertions(+)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
>>>>>>> index 5604701..13e5152 100644
>>>>>>> --- a/drivers/gpu/drm/i915/intel_display.c
>>>>>>> +++ b/drivers/gpu/drm/i915/intel_display.c
>>>>>>> @@ -47,6 +47,7 @@
>>>>>>>  #include <drm/drm_rect.h>
>>>>>>>  #include <linux/dma_remapping.h>
>>>>>>>  #include <linux/reservation.h>
>>>>>>> +#include <asm/iosf_mbi.h>
>>>>>>>
>>>>>>>  static bool is_mmio_work(struct intel_flip_work *work)
>>>>>>>  {
>>>>>>> @@ -6421,6 +6422,8 @@ static void valleyview_set_cdclk(struct drm_device *dev, int cdclk)
>>>>>>>          cmd = 0;
>>>>>>>
>>>>>>>      mutex_lock(&dev_priv->rps.hw_lock);
>>>>>>> +    iosf_mbi_punit_acquire();
>>>>>>> +
>>>>>>>      val = vlv_punit_read(dev_priv, PUNIT_REG_DSPFREQ);
>>>>>>>      val &= ~DSPFREQGUAR_MASK;
>>>>>>>      val |= (cmd << DSPFREQGUAR_SHIFT);
>>>>>>> @@ -6430,6 +6433,7 @@ static void valleyview_set_cdclk(struct drm_device *dev, int cdclk)
>>>>>>>               50)) {
>>>>>>>          DRM_ERROR("timed out waiting for CDclk change\n");
>>>>>>>      }
>>>>>>> +    iosf_mbi_punit_release();
>>>>>>>      mutex_unlock(&dev_priv->rps.hw_lock);
>>>>>>>
>>>>>>>      mutex_lock(&dev_priv->sb_lock);
>>>>>>> @@ -6497,6 +6501,7 @@ static void cherryview_set_cdclk(struct drm_device *dev, int cdclk)
>>>>>>>      cmd = DIV_ROUND_CLOSEST(dev_priv->hpll_freq << 1, cdclk) - 1;
>>>>>>>
>>>>>>>      mutex_lock(&dev_priv->rps.hw_lock);
>>>>>>> +    iosf_mbi_punit_acquire();
>>>>>>>      val = vlv_punit_read(dev_priv, PUNIT_REG_DSPFREQ);
>>>>>>>      val &= ~DSPFREQGUAR_MASK_CHV;
>>>>>>>      val |= (cmd << DSPFREQGUAR_SHIFT_CHV);
>>>>>>> @@ -6506,6 +6511,7 @@ static void cherryview_set_cdclk(struct drm_device *dev, int cdclk)
>>>>>>>               50)) {
>>>>>>>          DRM_ERROR("timed out waiting for CDclk change\n");
>>>>>>>      }
>>>>>>> +    iosf_mbi_punit_release();
>>>>>>>      mutex_unlock(&dev_priv->rps.hw_lock);
>>>>>>>
>>>>>>>      intel_update_cdclk(dev_priv);
>>>>>>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>>>>>>> index 249623d..adff84a 100644
>>>>>>> --- a/drivers/gpu/drm/i915/intel_pm.c
>>>>>>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>>>>>>> @@ -32,6 +32,7 @@
>>>>>>>  #include "../../../platform/x86/intel_ips.h"
>>>>>>>  #include <linux/module.h>
>>>>>>>  #include <drm/drm_atomic_helper.h>
>>>>>>> +#include <asm/iosf_mbi.h>
>>>>>>>
>>>>>>>  /**
>>>>>>>   * DOC: RC6
>>>>>>> @@ -276,6 +277,7 @@ static void chv_set_memory_dvfs(struct drm_i915_private *dev_priv, bool enable)
>>>>>>>      u32 val;
>>>>>>>
>>>>>>>      mutex_lock(&dev_priv->rps.hw_lock);
>>>>>>> +    iosf_mbi_punit_acquire();
>>>>>>>
>>>>>>>      val = vlv_punit_read(dev_priv, PUNIT_REG_DDR_SETUP2);
>>>>>>>      if (enable)
>>>>>>> @@ -290,6 +292,7 @@ static void chv_set_memory_dvfs(struct drm_i915_private *dev_priv, bool enable)
>>>>>>>                FORCE_DDR_FREQ_REQ_ACK) == 0, 3))
>>>>>>>          DRM_ERROR("timed out waiting for Punit DDR DVFS request\n");
>>>>>>>
>>>>>>> +    iosf_mbi_punit_release();
>>>>>>>      mutex_unlock(&dev_priv->rps.hw_lock);
>>>>>>>  }
>>>>>>>
>>>>>>> @@ -298,6 +301,7 @@ static void chv_set_memory_pm5(struct drm_i915_private *dev_priv, bool enable)
>>>>>>>      u32 val;
>>>>>>>
>>>>>>>      mutex_lock(&dev_priv->rps.hw_lock);
>>>>>>> +    iosf_mbi_punit_acquire();
>>>>>>>
>>>>>>>      val = vlv_punit_read(dev_priv, PUNIT_REG_DSPFREQ);
>>>>>>>      if (enable)
>>>>>>> @@ -306,6 +310,7 @@ static void chv_set_memory_pm5(struct drm_i915_private *dev_priv, bool enable)
>>>>>>>          val &= ~DSP_MAXFIFO_PM5_ENABLE;
>>>>>>>      vlv_punit_write(dev_priv, PUNIT_REG_DSPFREQ, val);
>>>>>>>
>>>>>>> +    iosf_mbi_punit_release();
>>>>>>>      mutex_unlock(&dev_priv->rps.hw_lock);
>>>>>>>  }
>>>>>>>
>>>>>>> @@ -4553,6 +4558,7 @@ void vlv_wm_get_hw_state(struct drm_device *dev)
>>>>>>>
>>>>>>>      if (IS_CHERRYVIEW(dev_priv)) {
>>>>>>>          mutex_lock(&dev_priv->rps.hw_lock);
>>>>>>> +        iosf_mbi_punit_acquire();
>>>>>>>
>>>>>>>          val = vlv_punit_read(dev_priv, PUNIT_REG_DSPFREQ);
>>>>>>>          if (val & DSP_MAXFIFO_PM5_ENABLE)
>>>>>>> @@ -4582,6 +4588,7 @@ void vlv_wm_get_hw_state(struct drm_device *dev)
>>>>>>>                  wm->level = VLV_WM_LEVEL_DDR_DVFS;
>>>>>>>          }
>>>>>>>
>>>>>>> +        iosf_mbi_punit_release();
>>>>>>>          mutex_unlock(&dev_priv->rps.hw_lock);
>>>>>>>      }
>>>>>>>
>>>>>>> @@ -4988,7 +4995,9 @@ static void valleyview_set_rps(struct drm_i915_private *dev_priv, u8 val)
>>>>>>>      I915_WRITE(GEN6_PMINTRMSK, gen6_rps_pm_mask(dev_priv, val));
>>>>>>>
>>>>>>>      if (val != dev_priv->rps.cur_freq) {
>>>>>>> +        iosf_mbi_punit_acquire();
>>>>>>>          vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ, val);
>>>>>>> +        iosf_mbi_punit_release();
>>>>>>>          if (!IS_CHERRYVIEW(dev_priv))
>>>>>>>              gen6_set_rps_thresholds(dev_priv, val);
>>>>>>>      }
>>>>>>> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
>>>>>>> index c0b7e95..e66bcc8 100644
>>>>>>> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
>>>>>>> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
>>>>>>> @@ -28,6 +28,7 @@
>>>>>>>
>>>>>>>  #include <linux/pm_runtime.h>
>>>>>>>  #include <linux/vgaarb.h>
>>>>>>> +#include <asm/iosf_mbi.h>
>>>>>>>
>>>>>>>  #include "i915_drv.h"
>>>>>>>  #include "intel_drv.h"
>>>>>>> @@ -1027,6 +1028,8 @@ static void vlv_set_power_well(struct drm_i915_private *dev_priv,
>>>>>>>      if (COND)
>>>>>>>          goto out;
>>>>>>>
>>>>>>> +    iosf_mbi_punit_acquire();
>>>>>>> +
>>>>>>>      ctrl = vlv_punit_read(dev_priv, PUNIT_REG_PWRGT_CTRL);
>>>>>>>      ctrl &= ~mask;
>>>>>>>      ctrl |= state;
>>>>>>> @@ -1037,6 +1040,8 @@ static void vlv_set_power_well(struct drm_i915_private *dev_priv,
>>>>>>>                state,
>>>>>>>                vlv_punit_read(dev_priv, PUNIT_REG_PWRGT_CTRL));
>>>>>>>
>>>>>>> +    iosf_mbi_punit_release();
>>>>>>> +
>>>>>>>  #undef COND
>>>>>>>
>>>>>>>  out:
>>>>>>> @@ -1643,6 +1648,8 @@ static void chv_set_pipe_power_well(struct drm_i915_private *dev_priv,
>>>>>>>      if (COND)
>>>>>>>          goto out;
>>>>>>>
>>>>>>> +    iosf_mbi_punit_acquire();
>>>>>>> +
>>>>>>>      ctrl = vlv_punit_read(dev_priv, PUNIT_REG_DSPFREQ);
>>>>>>>      ctrl &= ~DP_SSC_MASK(pipe);
>>>>>>>      ctrl |= enable ? DP_SSC_PWR_ON(pipe) : DP_SSC_PWR_GATE(pipe);
>>>>>>> @@ -1653,6 +1660,8 @@ static void chv_set_pipe_power_well(struct drm_i915_private *dev_priv,
>>>>>>>                state,
>>>>>>>                vlv_punit_read(dev_priv, PUNIT_REG_DSPFREQ));
>>>>>>>
>>>>>>> +    iosf_mbi_punit_release();
>>>>>>> +
>>>>>>>  #undef COND
>>>>>>>
>>>>>>>  out:
>>>>>>> --
>>>>>>> 2.9.3
>>>>>>
>>>
>
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