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

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Date:   Wed, 25 Apr 2018 14:41:11 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Lina Iyer <ilina@...eaurora.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 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'?

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