On Mon, 27 Mar 2023 10:47:25 -0700, Rodrigo Vivi wrote: > Hi Rodrigo, Sorry for the delay, I got pulled away into a couple of other things and could only now get back to this. > > +Daniel > > On Mon, Mar 27, 2023 at 09:58:52AM -0700, Dixit, Ashutosh wrote: > > On Sun, 26 Mar 2023 04:52:59 -0700, Rodrigo Vivi wrote: > > > > > > > Hi Rodrigo, > > > > > On Fri, Mar 24, 2023 at 04:31:22PM -0700, Dixit, Ashutosh wrote: > > > > On Fri, 24 Mar 2023 11:15:02 -0700, Belgaumkar, Vinay wrote: > > > > > > > > > > > > > Hi Vinay, > > > > > > > > Thanks for the review. Comments inline below. > > > > > > > > > On 3/15/2023 8:59 PM, Ashutosh Dixit wrote: > > > > > > On dGfx, the PL1 power limit being enabled and set to a low value results > > > > > > in a low GPU operating freq. It also negates the freq raise operation which > > > > > > is done before GuC firmware load. As a result GuC firmware load can time > > > > > > out. Such timeouts were seen in the GL #8062 bug below (where the PL1 power > > > > > > limit was enabled and set to a low value). Therefore disable the PL1 power > > > > > > limit when allowed by HW when loading GuC firmware. > > > > > v3 label missing in subject. > > > > > > > > > > > > v2: > > > > > > - Take mutex (to disallow writes to power1_max) across GuC reset/fw load > > > > > > - Add hwm_power_max_restore to error return code path > > > > > > > > > > > > v3 (Jani N): > > > > > > - Add/remove explanatory comments > > > > > > - Function renames > > > > > > - Type corrections > > > > > > - Locking annotation > > > > > > > > > > > > Link: https://gitlab.freedesktop.org/drm/intel/-/issues/8062 > > > > > > Signed-off-by: Ashutosh Dixit <ashutosh.dixit@xxxxxxxxx> > > > > > > --- > > > > > > drivers/gpu/drm/i915/gt/uc/intel_uc.c | 9 +++++++ > > > > > > drivers/gpu/drm/i915/i915_hwmon.c | 39 +++++++++++++++++++++++++++ > > > > > > drivers/gpu/drm/i915/i915_hwmon.h | 7 +++++ > > > > > > 3 files changed, 55 insertions(+) > > > > > > > > > > > > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c > > > > > > index 4ccb4be4c9cba..aa8e35a5636a0 100644 > > > > > > --- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c > > > > > > +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c > > > > > > @@ -18,6 +18,7 @@ > > > > > > #include "intel_uc.h" > > > > > > #include "i915_drv.h" > > > > > > +#include "i915_hwmon.h" > > > > > > static const struct intel_uc_ops uc_ops_off; > > > > > > static const struct intel_uc_ops uc_ops_on; > > > > > > @@ -461,6 +462,7 @@ static int __uc_init_hw(struct intel_uc *uc) > > > > > > struct intel_guc *guc = &uc->guc; > > > > > > struct intel_huc *huc = &uc->huc; > > > > > > int ret, attempts; > > > > > > + bool pl1en; > > > > > > > > > > Init to 'false' here > > > > > > > > See next comment. > > > > > > > > > > > > > > > > > > > > GEM_BUG_ON(!intel_uc_supports_guc(uc)); > > > > > > GEM_BUG_ON(!intel_uc_wants_guc(uc)); > > > > > > @@ -491,6 +493,9 @@ static int __uc_init_hw(struct intel_uc *uc) > > > > > > else > > > > > > attempts = 1; > > > > > > + /* Disable a potentially low PL1 power limit to allow freq to be > > > > > > raised */ > > > > > > + i915_hwmon_power_max_disable(gt->i915, &pl1en); > > > > > > + > > > > > > intel_rps_raise_unslice(&uc_to_gt(uc)->rps); > > > > > > while (attempts--) { > > > > > > @@ -547,6 +552,8 @@ static int __uc_init_hw(struct intel_uc *uc) > > > > > > intel_rps_lower_unslice(&uc_to_gt(uc)->rps); > > > > > > } > > > > > > + i915_hwmon_power_max_restore(gt->i915, pl1en); > > > > > > + > > > > > > guc_info(guc, "submission %s\n", str_enabled_disabled(intel_uc_uses_guc_submission(uc))); > > > > > > guc_info(guc, "SLPC %s\n", str_enabled_disabled(intel_uc_uses_guc_slpc(uc))); > > > > > > @@ -563,6 +570,8 @@ static int __uc_init_hw(struct intel_uc *uc) > > > > > > /* Return GT back to RPn */ > > > > > > intel_rps_lower_unslice(&uc_to_gt(uc)->rps); > > > > > > + i915_hwmon_power_max_restore(gt->i915, pl1en); > > > > > > > > > > if (pl1en) > > > > > > > > > > i915_hwmon_power_max_enable(). > > > > > > > > IMO it's better not to have checks in the main __uc_init_hw() function (if > > > > we do this we'll need to add 2 checks in __uc_init_hw()). If you really > > > > want we could do something like this inside > > > > i915_hwmon_power_max_disable/i915_hwmon_power_max_restore. But for now I > > > > am not making any changes. > > > > > > > > (I can send a patch with the changes if you want to take a look but IMO it > > > > will add more logic/code but without real benefits (it will save a rmw if > > > > the limit was already disabled, but IMO this code is called so infrequently > > > > (only during GuC resets) as to not have any significant impact)). > > > > > > > > > > > > > > > + > > > > > > __uc_sanitize(uc); > > > > > > if (!ret) { > > > > > > diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c > > > > > > index ee63a8fd88fc1..769b5bda4d53f 100644 > > > > > > --- a/drivers/gpu/drm/i915/i915_hwmon.c > > > > > > +++ b/drivers/gpu/drm/i915/i915_hwmon.c > > > > > > @@ -444,6 +444,45 @@ hwm_power_write(struct hwm_drvdata *ddat, u32 attr, int chan, long val) > > > > > > } > > > > > > } > > > > > > +void i915_hwmon_power_max_disable(struct drm_i915_private *i915, bool > > > > > > *old) > > > > > Shouldn't we call this i915_hwmon_package_pl1_disable()? > > > > > > > > I did think of using "pl1" in the function name but then decided to retain > > > > "power_max" because other hwmon functions for PL1 limit also use > > > > "power_max" (hwm_power_max_read/hwm_power_max_write) and currently > > > > "hwmon_power_max" is mapped to the PL1 limit. So "power_max" is used to > > > > show that all these functions deal with the PL1 power limit. > > > > > > > > There is a comment in __uc_init_hw() explaining "power_max" means the PL1 > > > > power limit. > > > > > > > > > > + __acquires(i915->hwmon->hwmon_lock) > > > > > > +{ > > > > > > + struct i915_hwmon *hwmon = i915->hwmon; > > > > > > + intel_wakeref_t wakeref; > > > > > > + u32 r; > > > > > > + > > > > > > + if (!hwmon || !i915_mmio_reg_valid(hwmon->rg.pkg_rapl_limit)) > > > > > > + return; > > > > > > + > > > > > > + /* Take mutex to prevent concurrent hwm_power_max_write */ > > > > > > + mutex_lock(&hwmon->hwmon_lock); > > > > > > + > > > > > > + with_intel_runtime_pm(hwmon->ddat.uncore->rpm, wakeref) > > > > > > + r = intel_uncore_rmw(hwmon->ddat.uncore, > > > > > > + hwmon->rg.pkg_rapl_limit, > > > > > > + PKG_PWR_LIM_1_EN, 0); > > > > > Most of this code (lock and rmw parts) is already inside static void > > > > > hwm_locked_with_pm_intel_uncore_rmw() , can we reuse that here? > > > > > > > > This was the case in v1 of the patch: > > > > > > > > https://patchwork.freedesktop.org/patch/526393/?series=115003&rev=1 > > > > > > > > But now this cannot be done because if you notice we acquire the mutex in > > > > i915_hwmon_power_max_disable() and release the mutex in > > > > i915_hwmon_power_max_restore(). > > > > > > > > I explained the reason why this the mutex is handled this way in my reply > > > > to Jani Nikula here: > > > > > > > > https://patchwork.freedesktop.org/patch/526598/?series=115003&rev=2 > > > > > > > > Quoting below: > > > > > > > > ``` > > > > > > + /* hwmon_lock mutex is unlocked in hwm_power_max_restore */ > > > > > > > > > > Not too happy about that... any better ideas? > > > > > > > > Afais, taking the mutex is the only fully correct solution (when we disable > > > > the power limit, userspace can go re-enable it). Examples of partly > > > > incorrect solutions (which don't take the mutex) include: > > > > > > > > a. Don't take the mutex, don't do anything, ignore any changes to the value > > > > if it has changed during GuC reset/fw load (just overwrite the changed > > > > value). Con: changed value is lost. > > > > > > > > b. Detect if the value has changed (the limit has been re-enabled) after we > > > > have disabled the limit and in that case skip restoring the value. But > > > > then someone can say why do we allow enabling the PL1 limit since we > > > > want to disable it. > > > > > > > > Both these are very unlikely scenarios so they might work. But I would > > > > first like to explore if holding a mutex across GuC reset is prolebmatic > > > > since that is /the/ correct solution. But if anyone comes up with a reason > > > > why that cannot be done we can look at these other not completely correct > > > > options. > > > > > > I see what you are doing and it looks indeed a very safe approach to ensure > > > the pl1 won't be toggled by other paths while we need some guaranteed state > > > here, or hw init fails badly. > > > > > > But in the end you are making your lock to protect the code from another path > > > and not protecting the data itself. The data was already protected in the > > > first version with the lock in the rmw. > > > > Sorry I am not really following. Daniel had mentioned this "protecting code > > vs protecting data" but I am wondering how it is applicable in this > > case. IMO here the data we are protecting is the register which we don't > > want written to by userland while GuC load is in progress. To do that we > > need to block the code path writing to register. So what we have here seems > > to me to be the simplest and cleanest approach for solving this issue. > > I believe your cases here is exactly what Daniel had mentioned as protecting > code and not data. Well, in the end we are of course protecting data to be > modified, but in your case you use that mutex to also protect the code path > and avoid other calls while you are in this guc_init_path... > > Please Daniel, correct me here if I got it wrong. > > What I don't like here is that we lock from one function and keep that for a > while and unlock from the other function. To protect the data itself in general > we just need for a very minimal time while we are modifying the data itself. > > > > > > maybe we need to have some kind of a state check with other state-lock and > > > then if we are in this forced state for init path, the request for the normal path > > > ignores and move one, > > > > I don't see how this will *not* be racy... > > maybe something like this?: > > at power_max_disable: > mutex_lock(data_lock); > > mutex_lock(state_lock); > state = in_use; > mutex_unlock(state_lock); > > mmio_rmw(); > mutex_unlock(data_lock); > > > at power_max_restoration: > > at power_max_disable: > mutex_lock(data_lock); > > mutex_lock(state_lock); > state = available; > mutex_unlock(state_lock); > > mmio_rmw(); > mutex_unlock(data_lock); > > at sysfs fn: > > mutex_lock(data_lock); > mutex_lock(state_lock); > if (state == in_use) { > ret = -EAGAIN > goto out; > } > mutex_unlock(state_lock); > > .... > > out: > > mutex_unlock(data_lock); Thanks for suggesting this, actually it worked out quite nicely and I have implemented this in the latest version. Though I believe state_lock is not needed (data_lock is sufficient) so I have skipped that. Please take a look at: https://patchwork.freedesktop.org/series/116172/ Thanks. -- Ashutosh > > > > > > or maybe we queue some request... > > > > Queuing a request will not be enough (even if this is possible), the > > request will need to wait to complete till GuC load completes. So we'll > > have to complete the request when GuC load completes, similar to releasing > > the mutex in the current patch. Looks like a much more complicated way of > > doing what the mutex does very simply. > > The wq would sleep/delay while state == in_use, then process the next request... > > > > > So: > > > > a. What is the real problem with the current implementation? > > probably the big lock used to protect the state machinery... > > but if other folks believe that we don't have an actual problem here > and this big lock is acceptable as long as it has the annotation for > the static analyzers, I'm okay to just let it go... > > > > > > b. What would be the correct solution for it? That is how, specifically, > > should we implement it? > > state handling with separated lock from the data itself is my suggestion. > > > > > Some more guidance will be helpful if you think this patch has issues. > > I hope Daniel and/or other i915 maintainers can jump here. Specially if > I'm being to paranoid and the current patch is enough... > > > > > Thanks. > > -- > > Ashutosh > > > > > > ``` > > > > > > > > > > + > > > > > > + *old = !!(r & PKG_PWR_LIM_1_EN); > > > > > > +} > > > > > > + > > > > > > +void i915_hwmon_power_max_restore(struct drm_i915_private *i915, bool old) > > > > > > + __releases(i915->hwmon->hwmon_lock) > > > > > We can just call this i915_hwmon_power_max_enable() and call whenever the > > > > > old value was actually enabled. That way, we have proper mirror functions. > > > > > > > > As I explained that would mean adding two checks in the main __uc_init_hw() > > > > function which I am trying to avoid. So we have disable/restore pair. > > > > > > > > > > +{ > > > > > > + struct i915_hwmon *hwmon = i915->hwmon; > > > > > > + intel_wakeref_t wakeref; > > > > > > + > > > > > > + if (!hwmon || !i915_mmio_reg_valid(hwmon->rg.pkg_rapl_limit)) > > > > > > + return; > > > > > > + > > > > > > + with_intel_runtime_pm(hwmon->ddat.uncore->rpm, wakeref) > > > > > > + intel_uncore_rmw(hwmon->ddat.uncore, > > > > > > + hwmon->rg.pkg_rapl_limit, > > > > > > + PKG_PWR_LIM_1_EN, > > > > > > + old ? PKG_PWR_LIM_1_EN : 0); > > > > > > > > > > 3rd param should be 0 here, else we will end up clearing other bits. > > > > > > > > No see intel_uncore_rmw(), it will only clear the PKG_PWR_LIM_1_EN bit, so > > > > the code here is correct. intel_uncore_rmw() does: > > > > > > > > val = (old & ~clear) | set; > > > > > > > > So for now I am not making any changes, if you feel strongly about > > > > something one way or another let me know. Anyway these comments should help > > > > you understand the patch better so take a look and we can go from there. > > > > > > > > Thanks. > > > > -- > > > > Ashutosh > > > > > > > > > > + > > > > > > + mutex_unlock(&hwmon->hwmon_lock); > > > > > > +} > > > > > > + > > > > > > static umode_t > > > > > > hwm_energy_is_visible(const struct hwm_drvdata *ddat, u32 attr) > > > > > > { > > > > > > diff --git a/drivers/gpu/drm/i915/i915_hwmon.h b/drivers/gpu/drm/i915/i915_hwmon.h > > > > > > index 7ca9cf2c34c96..0fcb7de844061 100644 > > > > > > --- a/drivers/gpu/drm/i915/i915_hwmon.h > > > > > > +++ b/drivers/gpu/drm/i915/i915_hwmon.h > > > > > > @@ -7,14 +7,21 @@ > > > > > > #ifndef __I915_HWMON_H__ > > > > > > #define __I915_HWMON_H__ > > > > > > +#include <linux/types.h> > > > > > > + > > > > > > struct drm_i915_private; > > > > > > +struct intel_gt; > > > > > > #if IS_REACHABLE(CONFIG_HWMON) > > > > > > void i915_hwmon_register(struct drm_i915_private *i915); > > > > > > void i915_hwmon_unregister(struct drm_i915_private *i915); > > > > > > +void i915_hwmon_power_max_disable(struct drm_i915_private *i915, bool *old); > > > > > > +void i915_hwmon_power_max_restore(struct drm_i915_private *i915, bool old); > > > > > > #else > > > > > > static inline void i915_hwmon_register(struct drm_i915_private *i915) { }; > > > > > > static inline void i915_hwmon_unregister(struct drm_i915_private *i915) { }; > > > > > > +static inline void i915_hwmon_power_max_disable(struct drm_i915_private *i915, bool *old) { }; > > > > > > +static inline void i915_hwmon_power_max_restore(struct drm_i915_private *i915, bool old) { }; > > > > > > #endif > > > > > > #endif /* __I915_HWMON_H__ */
