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    SubjectRe: [PATCH] clk: qcom: clk-rpmh: Wait for completion when enabling clocks
    On Fri 14 Feb 18:12 PST 2020, Mike Tipton wrote:

    > The current implementation always uses rpmh_write_async, which doesn't
    > wait for completion. That's fine for disable requests since there's no
    > immediate need for the clocks and they can be disabled in the
    > background. However, for enable requests we need to ensure the clocks
    > are actually enabled before returning to the client. Otherwise, clients
    > can end up accessing their HW before the necessary clocks are enabled,
    > which can lead to bus errors.
    >
    > Use the synchronous version of this API (rpmh_write) for enable requests
    > in the active set to ensure completion.
    >
    > Completion isn't required for sleep/wake sets, since they don't take
    > effect until after we enter sleep. All rpmh requests are automatically
    > flushed prior to entering sleep.
    >
    > Fixes: 9c7e47025a6b ("clk: qcom: clk-rpmh: Add QCOM RPMh clock driver")
    > Signed-off-by: Mike Tipton <mdtipton@codeaurora.org>

    Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

    Regards,
    Bjorn

    > ---
    > drivers/clk/qcom/clk-rpmh.c | 18 ++++++++++++++++--
    > 1 file changed, 16 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/clk/qcom/clk-rpmh.c b/drivers/clk/qcom/clk-rpmh.c
    > index 12bd8715dece..3137595a736b 100644
    > --- a/drivers/clk/qcom/clk-rpmh.c
    > +++ b/drivers/clk/qcom/clk-rpmh.c
    > @@ -143,6 +143,19 @@ static inline bool has_state_changed(struct clk_rpmh *c, u32 state)
    > != (c->aggr_state & BIT(state));
    > }
    >
    > +static int clk_rpmh_send(struct clk_rpmh *c, enum rpmh_state state,
    > + struct tcs_cmd *cmd, bool wait_for_completion)
    > +{
    > + int ret;
    > +
    > + if (wait_for_completion)
    > + ret = rpmh_write(c->dev, state, cmd, 1);
    > + else
    > + ret = rpmh_write_async(c->dev, state, cmd, 1);
    > +
    > + return ret;
    > +}
    > +
    > static int clk_rpmh_send_aggregate_command(struct clk_rpmh *c)
    > {
    > struct tcs_cmd cmd = { 0 };
    > @@ -159,7 +172,8 @@ static int clk_rpmh_send_aggregate_command(struct clk_rpmh *c)
    > if (cmd_state & BIT(state))
    > cmd.data = on_val;
    >
    > - ret = rpmh_write_async(c->dev, state, &cmd, 1);
    > + ret = clk_rpmh_send(c, state, &cmd,
    > + cmd_state && state == RPMH_ACTIVE_ONLY_STATE);
    > if (ret) {
    > dev_err(c->dev, "set %s state of %s failed: (%d)\n",
    > !state ? "sleep" :
    > @@ -267,7 +281,7 @@ static int clk_rpmh_bcm_send_cmd(struct clk_rpmh *c, bool enable)
    > cmd.addr = c->res_addr;
    > cmd.data = BCM_TCS_CMD(1, enable, 0, cmd_state);
    >
    > - ret = rpmh_write_async(c->dev, RPMH_ACTIVE_ONLY_STATE, &cmd, 1);
    > + ret = clk_rpmh_send(c, RPMH_ACTIVE_ONLY_STATE, &cmd, enable);
    > if (ret) {
    > dev_err(c->dev, "set active state of %s failed: (%d)\n",
    > c->res_name, ret);
    > --
    > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
    > a Linux Foundation Collaborative Project

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