linux-kernel - Re: [PATCH v2 05/10] drivers: qcom: rpmh-rsc: write sleep/wake requests to TCS

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Message-ID: <CAE=gft5vEa69ML7mu=-=dg8Djb5dGdbs01PnwAYcJmSPioNasg@mail.gmail.com>
Date:   Fri, 16 Feb 2018 15:50:29 -0800
From:   Evan Green <evgreen@...omium.org>
To:     Lina Iyer <ilina@...eaurora.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 05/10] drivers: qcom: rpmh-rsc: write sleep/wake
 requests to TCS

Hello Lina,

On Thu, Feb 15, 2018 at 9:35 AM, Lina Iyer <ilina@...eaurora.org> 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 job of this controller
> driver to find arrange the requests into the available TCSes.
>
> Signed-off-by: Lina Iyer <ilina@...eaurora.org>
> ---
>  drivers/soc/qcom/rpmh-internal.h |   7 +++
>  drivers/soc/qcom/rpmh-rsc.c      | 126 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 133 insertions(+)
>
[...]
> +static int find_slots(struct tcs_group *tcs, struct tcs_request *msg,
> +                    int *m, int *n)
> +{
> +       int slot, offset;
> +       int i = 0;
> +
> +       /* Find if we already have the msg in our TCS */
> +       slot = find_match(tcs, msg->payload, msg->num_payload);
> +       if (slot >= 0)
> +               goto copy_data;
> +
> +       /* Do over, until we can fit the full payload in a TCS */
> +       do {
> +               slot = bitmap_find_next_zero_area(tcs->slots, MAX_TCS_SLOTS,
> +                                                i, msg->num_payload, 0);
> +               if (slot == MAX_TCS_SLOTS)
> +                       break;
> +               i += tcs->ncpt;
> +       } while (slot + msg->num_payload - 1 >= i);
> +
> +       if (slot == MAX_TCS_SLOTS)
> +               return -ENOMEM;
> +
> +copy_data:
> +       bitmap_set(tcs->slots, slot, msg->num_payload);
> +       /* Copy the addresses of the resources over to the slots */
> +       for (i = 0; tcs->cmd_addr && i < msg->num_payload; i++)

I don't think tcs->cmd_addr can be null, can it? Above, find_match()
is already reaching through cmd_addr with enthusiasm. If kept, it
could at least be moved outside of the loop.

Evan