Messages in this thread |  | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH v2 0/3] powernv:stop: Use psscr_val,mask provided by firmware | Date | Tue, 01 Nov 2016 05:21:05 +0100 |
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On Thursday, October 27, 2016 02:05:04 PM Gautham R. Shenoy wrote: > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> > > Hi, > > This is the second iteration of the patchset to use the psscr_val and > psscr_mask provided by the firmware for each of the stop states. > > The previous version can be found here: > https://lkml.org/lkml/2016/9/29/45 > > The main changes in this version are: > > 1) Add a helper function in powernv-cpuidle.c to help initialize the > powernv_states cpuidle table. > > 2) Handle the older firmware which populates only the Requested Level > (RL) fields of the psscr and psscr_mask in the device tree. This > patchset ensures that in the presence of the older firmware, the > other fields of PSSCR are initalized to sane default values. > > > Synopsis > ========== > In the current implementation, the code for ISA v3.0 stop > implementation has a couple of shortcomings. > > a) The code hand-codes the values for ESL,EC,TR,MTL bits of PSSCR and > uses only the RL field from the firmware. While this is not > incorrect, since the hand-coded values are legitimate, it is not a > very flexible design since the firmware has the capability to > communicate these values via the "ibm,cpu-idle-state-psscr" and > "ibm,cpu-idle-state-psscr-mask" properties. In case where the > firmware provides values for these fields that is different from > the hand-coded values, the current code will not work as intended. > > b) Due to issue a), the current code assumes that ESL=EC=1 for all the > stop states and hence the wakeup from the stop instruction will > happen at 0x100, the system-reset vector. However, the ISA v3.0 > allows the ESL=EC=0 behaviour where the corresponding stop-state > loses no state and wakes up from the subsequent instruction. The > current code doesn't handle this case. > > This patch series addresses these issues. > > The first patch in the series renames the existing > IDLE_STATE_ENTER_SEQ macro to IDLE_STATE_ENTER_SEQ_NORET. It reuses > the name IDLE_STATE_ENTER_SEQ for entering into stop-states which wake > up at the subsequent instruction. > > The second patch adds a helper function in cpuidle-powernv.c for > initializing entries of the powernv_states[] table that is passed to > the cpu-idle core. This eliminates some of the code duplication in the > function that discovers and initializes the stop states. > > The third patch in the series fixes issues a) and b) by ensuring that > the psscr-value and the psscr-mask provided by the firmware are what > will be used to set a particular stop state. It also adds support for > handling wake-up from stop states which were entered with ESL=EC=0. > > The third patch also handles the older firmware which sets only the > Requested Level (RL) field in the psscr and psscr-mask exposed in the > device tree. In the presence of such older firmware, this patch will > set the default sane values for for remaining PSSCR fields (i.e PSLL, > MTL, ESL, EC, and TR). > > The skiboot patch populates all the relevant fields in the PSSCR > values and the mask for all the stop states can be found here: > https://lists.ozlabs.org/pipermail/skiboot/2016-September/004869.html > > The patches are based on top of > git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git fixes > > Gautham R. Shenoy (3): > powernv:idle: Add IDLE_STATE_ENTER_SEQ_NORET macro > cpuidle:powernv: Add helper function to populate powernv idle states. > powernv: Pass PSSCR value and mask to power9_idle_stop
OK
I need someone to review this for me.
Thanks, Rafael
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