linux-kernel - Re: [PATCH v6 05/10] drivers: qcom: rpmh-rsc: write sleep/wake requests to TCS

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Message-ID: <20180427173943.GD6380@codeaurora.org>
Date:   Fri, 27 Apr 2018 11:39:43 -0600
From:   Lina Iyer <ilina@...eaurora.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     andy.gross@...aro.org, david.brown@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        rnayak@...eaurora.org, bjorn.andersson@...aro.org,
        linux-kernel@...r.kernel.org, sboyd@...nel.org,
        evgreen@...omium.org, dianders@...omium.org
Subject: Re: [PATCH v6 05/10] drivers: qcom: rpmh-rsc: write sleep/wake
 requests to TCS

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@...eaurora.org>
>> Reviewed-by: Evan Green <evgreen@...omium.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.

-- Lina

>> +				return -EINVAL;
>> +			} else if (j == len - 1) {
>> +				return i;
>> +			}
>> +		}
>> +	}
>> +
>> +	return -ENODATA;
>> +}