| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <CAGETcx-CX7aR66XAvZbD9MLeLgtbPPHaFaAOY5f-OqOcWLGndw@mail.gmail.com>
Date: Mon, 25 Nov 2019 17:40:46 -0800
From: Saravana Kannan <saravanak@...gle.com>
To: Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>
Cc: Android Kernel Team <kernel-team@...roid.com>,
linux-clk@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] clk: Keep boot clocks on for multiple consumers
On Mon, Nov 18, 2019 at 3:42 PM Saravana Kannan <saravanak@...gle.com> wrote:
>
> Clocks can turned on (by the hardware, bootloader, etc) upon a
> reset/boot of a hardware platform. These "boot clocks" could be clocking
> devices that are active before the kernel starts running. For example,
> clocks needed for the interconnects, UART console, display, CPUs, DDR,
> etc.
>
> When a boot clock is used by more than one consumer or multiple boot
> clocks share a parent clock, the boot clock (or the common parent) can
> be turned off when the first consumer probes. This can potentially crash
> the device or cause poor user experience.
>
> This patch fixes this by explicitly enabling the boot clocks during
> clock registration and then disabling them at late_initcall_sync(). This
> gives all the consumers until late_initcall() to put their "votes" in to
> keep any of the boot clocks on past late_initcall().
>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
> drivers/clk/clk.c | 62 ++++++++++++++++++++++++++++++++++++
> include/linux/clk-provider.h | 1 +
> 2 files changed, 63 insertions(+)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 1c677d7f7f53..a1b09c9f8845 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -72,6 +72,8 @@ struct clk_core {
> unsigned long flags;
> bool orphan;
> bool rpm_enabled;
> + bool state_held;
> + bool boot_enabled;
> unsigned int enable_count;
> unsigned int prepare_count;
> unsigned int protect_count;
> @@ -1300,6 +1302,36 @@ static int clk_disable_unused(void)
> }
> late_initcall_sync(clk_disable_unused);
>
> +static void clk_unprepare_disable_subtree(struct clk_core *core)
> +{
> + struct clk_core *child;
> +
> + lockdep_assert_held(&prepare_lock);
> +
> + hlist_for_each_entry(child, &core->children, child_node)
> + clk_unprepare_disable_subtree(child);
> +
> + if (!core->state_held)
> + return;
> +
> + clk_core_disable_unprepare(core);
> +}
> +
> +static int clk_release_boot_state(void)
> +{
> + struct clk_core *core;
> +
> + clk_prepare_lock();
> +
> + hlist_for_each_entry(core, &clk_root_list, child_node)
> + clk_unprepare_disable_subtree(core);
> +
> + clk_prepare_unlock();
> +
> + return 0;
> +}
> +late_initcall_sync(clk_release_boot_state);
> +
> static int clk_core_determine_round_nolock(struct clk_core *core,
> struct clk_rate_request *req)
> {
> @@ -1674,6 +1706,30 @@ static int clk_fetch_parent_index(struct clk_core *core,
> return i;
> }
>
> +static void clk_core_hold_state(struct clk_core *core)
> +{
> + if (core->state_held || !core->boot_enabled ||
> + core->flags & CLK_DONT_HOLD_STATE)
> + return;
> +
> + WARN(core->orphan, "%s: Can't hold state for orphan clk\n", core->name);
> +
> + core->state_held = !clk_core_prepare_enable(core);
> +}
> +
> +static void __clk_core_update_orphan_hold_state(struct clk_core *core)
> +{
> + struct clk_core *child;
> +
> + if (core->orphan)
> + return;
> +
> + clk_core_hold_state(core);
> +
> + hlist_for_each_entry(child, &core->children, child_node)
> + __clk_core_update_orphan_hold_state(child);
> +}
> +
> /*
> * Update the orphan status of @core and all its children.
> */
> @@ -3374,6 +3430,8 @@ static int __clk_core_init(struct clk_core *core)
> rate = 0;
> core->rate = core->req_rate = rate;
>
> + core->boot_enabled = clk_core_is_enabled(core);
> +
> /*
> * Enable CLK_IS_CRITICAL clocks so newly added critical clocks
> * don't get accidentally disabled when walking the orphan tree and
> @@ -3389,6 +3447,9 @@ static int __clk_core_init(struct clk_core *core)
> clk_enable_unlock(flags);
> }
>
> + if (!core->orphan)
> + clk_core_hold_state(core);
> +
> /*
> * walk the list of orphan clocks and reparent any that newly finds a
> * parent.
> @@ -3408,6 +3469,7 @@ static int __clk_core_init(struct clk_core *core)
> __clk_set_parent_after(orphan, parent, NULL);
> __clk_recalc_accuracies(orphan);
> __clk_recalc_rates(orphan, 0);
> + __clk_core_update_orphan_hold_state(orphan);
> }
> }
>
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 2fdfe8061363..f0e522ea793f 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -32,6 +32,7 @@
> #define CLK_OPS_PARENT_ENABLE BIT(12)
> /* duty cycle call may be forwarded to the parent clock */
> #define CLK_DUTY_CYCLE_PARENT BIT(13)
> +#define CLK_DONT_HOLD_STATE BIT(14) /* Don't hold state */
>
> struct clk;
> struct clk_hw;
> --
> 2.24.0.432.g9d3f5f5b63-goog
>
Stephen,
Nudge, nudge. Thoughts?
-Saravana
Powered by blists - more mailing lists