Messages in this thread | | | Date | Fri, 27 Apr 2018 13:45:59 -0600 | From | Lina Iyer <> | Subject | Re: [PATCH v6 05/10] drivers: qcom: rpmh-rsc: write sleep/wake requests to TCS |
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On Fri, Apr 27 2018 at 12:40 -0600, Matthias Kaehlcke wrote: >On Fri, Apr 27, 2018 at 11:39:43AM -0600, Lina Iyer wrote: >> On Wed, Apr 25 2018 at 15:41 -0600, Matthias Kaehlcke wrote: >> > On Thu, Apr 19, 2018 at 04:16:30PM -0600, Lina Iyer wrote: >> > > Sleep and wake requests are sent when the application processor >> > > subsystem of the SoC is entering deep sleep states like in suspend. >> > > These requests help lower the system power requirements when the >> > > resources are not in use. >> > > >> > > Sleep and wake requests are written to the TCS slots but are not >> > > triggered at the time of writing. The TCS are triggered by the firmware >> > > after the last of the CPUs has executed its WFI. Since these requests >> > > may come in different batches of requests, it is the job of this >> > > controller driver to find and arrange the requests into the available >> > > TCSes. >> > > >> > > Signed-off-by: Lina Iyer <ilina@codeaurora.org> >> > > Reviewed-by: Evan Green <evgreen@chromium.org> >> > > --- >> > > drivers/soc/qcom/rpmh-internal.h | 8 +++ >> > > drivers/soc/qcom/rpmh-rsc.c | 120 +++++++++++++++++++++++++++++++ >> > > 2 files changed, 128 insertions(+) >> > > >> > > diff --git a/drivers/soc/qcom/rpmh-internal.h b/drivers/soc/qcom/rpmh-internal.h >> > > index d9a21726e568..6e19fe458c31 100644 >> > > --- a/drivers/soc/qcom/rpmh-internal.h >> > > +++ b/drivers/soc/qcom/rpmh-internal.h >> > >> > <snip> >> > >> > > +static int find_match(const struct tcs_group *tcs, const struct tcs_cmd *cmd, >> > > + int len) >> > > +{ >> > > + int i, j; >> > > + >> > > + /* Check for already cached commands */ >> > > + for_each_set_bit(i, tcs->slots, MAX_TCS_SLOTS) { >> > > + for (j = 0; j < len; j++) { >> > > + if (tcs->cmd_cache[i] != cmd[0].addr) { >> > >> > Shouldn't the condition be 'tcs->cmd_cache[i + j] != cmd[j].addr'? >> > >> Here, we are trying to find the first address from the request and its >> position 'i' in the cmd_cache. >> >> > Otherwise the code below the following if branch will never be >> > executed. Either the 'tcs->cmd_cache[i] != cmd[0].addr' branch isn't >> > entered because the addresses match, or the addresses don't match >> > and the inner loop is aborted after the first iteration. >> > >> > > + if (j == 0) >> > > + break; >> > > + WARN(tcs->cmd_cache[i + j] != cmd[j].addr, >> > > + "Message does not match previous sequence.\n"); >> We now check for the sequence using the iterator 'j' only after we have >> found 'i' (the beginning of our request). >> >> I hope that helps clear the concern. > >It doesn't, maybe I'm just confused, the driver has a certain >complexity and I don't claim to have a comprehensive understanding :) > >If I understand correctly find_match() is used to find a sequence of >commands of length 'len' in the command cache. If that is correct I >would expect it to do the following: > >1. iterate through the commands in the command cache and find a >command that matches the first command in the sequence > >2. verify that the (len - 1) subsequent commands match those in the >sequence, otherwise bail out > >If I'm not mistaken the current version of find_match() only checks >that the first command exists. After that it happily increases the >command index, but doesn't perform any checks (after finding the first >command 'tcs->cmd_cache[i] != cmd[0].addr' remains false for the >subsequent values of j). When j reaches (len - 1) the function >returns the index of the first command in the cache, regardless of >whether the other commands match or not. > Did you miss the check inside the WARN? WARN(tcs->cmd_cache[i + j] != cmd[j].addr,
--Lina
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