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    Subject[PATCH 1/2] soc: qcom: aoss: Don't wait for IRQ if we might be in suspend/resume noirq
    Date
    Running suspend/resume tests on a sc7180-based board with a modem I
    found that both system suspend and system resume would hang for 1
    second. These messages indicate where:

    genpd genpd:0:4080000.remoteproc: calling genpd_suspend_noirq+0x0/0x2c @ 18659, parent: none
    genpd genpd:0:4080000.remoteproc: genpd_suspend_noirq+0x0/0x2c returned 0 after 987917 usecs

    Adding a printout, I found that we were working with the power domain
    where "res->pd.name" was "modem".

    I found that we were hanging on the wait_event_interruptible_timeout()
    call in qmp_send(). Specifically we'd wait for the whole 1 second
    timeout to hit, then we'd notice that our condition was true and would
    continue on our merry way. Sure enough, I could confirm that
    wait_event_interruptible_timeout() was returning "1" which indicates
    that the condition evaluated to true and we also timed out.

    Dumping the stack at the time of the failure made the problem clear.
    Specifically the stack looked like:
    qmp_send+0x1cc/0x210
    qmp_pd_power_toggle+0x90/0xb8
    qmp_pd_power_off+0x20/0x2c
    genpd_sync_power_off+0x80/0x12c
    genpd_finish_suspend+0xd8/0x108
    genpd_suspend_noirq+0x20/0x2c
    dpm_run_callback+0xe0/0x1d4
    __device_suspend_noirq+0xfc/0x200
    dpm_suspend_noirq+0x174/0x3bc
    suspend_devices_and_enter+0x198/0x8a0
    pm_suspend+0x550/0x6f4
    As you can see we're running from the "noirq" callback. Looking at
    what was supposed to wake us up, it was qmp_intr() (our IRQ handler).
    Doh!

    I believe that the correct fix here is to assume that our power_off /
    power_on functions might be called at "noirq" time and just always
    poll if we're called via that path. Other paths can continue to wait
    for the IRQ.

    Fixes: 2209481409b7 ("soc: qcom: Add AOSS QMP driver")
    Signed-off-by: Douglas Anderson <dianders@chromium.org>
    ---
    This problem was observed on the Chrome OS 5.4 tree which has some
    extra patches in it compared to mainline. The top of the current
    Qualcomm tree didn't have the delay, but that's probably because
    everything isn't fully enabled there yet. I at least confirmed that
    this patch doesn't actually _break_ anything on mainline, though.

    drivers/soc/qcom/qcom_aoss.c | 26 +++++++++++++++++++-------
    1 file changed, 19 insertions(+), 7 deletions(-)

    diff --git a/drivers/soc/qcom/qcom_aoss.c b/drivers/soc/qcom/qcom_aoss.c
    index ed2c687c16b3..818cdf74a267 100644
    --- a/drivers/soc/qcom/qcom_aoss.c
    +++ b/drivers/soc/qcom/qcom_aoss.c
    @@ -6,6 +6,7 @@
    #include <linux/clk-provider.h>
    #include <linux/interrupt.h>
    #include <linux/io.h>
    +#include <linux/iopoll.h>
    #include <linux/mailbox_client.h>
    #include <linux/module.h>
    #include <linux/platform_device.h>
    @@ -215,6 +216,8 @@ static bool qmp_message_empty(struct qmp *qmp)
    * @qmp: qmp context
    * @data: message to be sent
    * @len: length of the message
    + * @noirq: If true we might have been called from the "noirq" suspend/resume
    + * callbacks, so fall back to polling mode for waiting for completion.
    *
    * Transmit @data to AOSS and wait for the AOSS to acknowledge the message.
    * @len must be a multiple of 4 and not longer than the mailbox size. Access is
    @@ -222,11 +225,12 @@ static bool qmp_message_empty(struct qmp *qmp)
    *
    * Return: 0 on success, negative errno on failure
    */
    -static int qmp_send(struct qmp *qmp, const void *data, size_t len)
    +static int qmp_send(struct qmp *qmp, const void *data, size_t len, bool noirq)
    {
    long time_left;
    size_t tlen;
    int ret;
    + bool is_empty;

    if (WARN_ON(len + sizeof(u32) > qmp->size))
    return -EINVAL;
    @@ -245,8 +249,16 @@ static int qmp_send(struct qmp *qmp, const void *data, size_t len)
    tlen = readl(qmp->msgram + qmp->offset);
    qmp_kick(qmp);

    - time_left = wait_event_interruptible_timeout(qmp->event,
    - qmp_message_empty(qmp), HZ);
    + /*
    + * We may be called from a suspend/resume "noirq" context. In such
    + * a case we have no choice but to poll.
    + */
    + if (noirq)
    + time_left = readx_poll_timeout_atomic(qmp_message_empty, qmp,
    + is_empty, is_empty, 1U, 1000000U);
    + else
    + time_left = wait_event_interruptible_timeout(qmp->event,
    + qmp_message_empty(qmp), HZ);
    if (!time_left) {
    dev_err(qmp->dev, "ucore did not ack channel\n");
    ret = -ETIMEDOUT;
    @@ -267,7 +279,7 @@ static int qmp_qdss_clk_prepare(struct clk_hw *hw)
    static const char buf[QMP_MSG_LEN] = "{class: clock, res: qdss, val: 1}";
    struct qmp *qmp = container_of(hw, struct qmp, qdss_clk);

    - return qmp_send(qmp, buf, sizeof(buf));
    + return qmp_send(qmp, buf, sizeof(buf), false);
    }

    static void qmp_qdss_clk_unprepare(struct clk_hw *hw)
    @@ -275,7 +287,7 @@ static void qmp_qdss_clk_unprepare(struct clk_hw *hw)
    static const char buf[QMP_MSG_LEN] = "{class: clock, res: qdss, val: 0}";
    struct qmp *qmp = container_of(hw, struct qmp, qdss_clk);

    - qmp_send(qmp, buf, sizeof(buf));
    + qmp_send(qmp, buf, sizeof(buf), false);
    }

    static const struct clk_ops qmp_qdss_clk_ops = {
    @@ -321,7 +333,7 @@ static int qmp_pd_power_toggle(struct qmp_pd *res, bool enable)
    snprintf(buf, sizeof(buf),
    "{class: image, res: load_state, name: %s, val: %s}",
    res->pd.name, enable ? "on" : "off");
    - return qmp_send(res->qmp, buf, sizeof(buf));
    + return qmp_send(res->qmp, buf, sizeof(buf), true);
    }

    static int qmp_pd_power_on(struct generic_pm_domain *domain)
    @@ -438,7 +450,7 @@ static int qmp_cdev_set_cur_state(struct thermal_cooling_device *cdev,
    qmp_cdev->name,
    cdev_state ? "on" : "off");

    - ret = qmp_send(qmp_cdev->qmp, buf, sizeof(buf));
    + ret = qmp_send(qmp_cdev->qmp, buf, sizeof(buf), false);

    if (!ret)
    qmp_cdev->state = cdev_state;
    --
    2.28.0.163.g6104cc2f0b6-goog
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