linux-kernel - Re: [PATCH] clk: qcom: clk-rpmh: Wait for completion when enabling clocks

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Message-ID: <158378825407.66766.14135857856613969751@swboyd.mtv.corp.google.com>
Date:   Mon, 09 Mar 2020 14:10:54 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Mike Tipton <mdtipton@...eaurora.org>, tdas@...eaurora.org
Cc:     bjorn.andersson@...aro.org, mturquette@...libre.com,
        agross@...nel.org, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mike Tipton <mdtipton@...eaurora.org>
Subject: Re: [PATCH] clk: qcom: clk-rpmh: Wait for completion when enabling clocks

Quoting Mike Tipton (2020-02-14 18:12:32)
> 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@...eaurora.org>
> ---

Applied to clk-next but I squashed in some changes to make it easier for
me to read.