From patchwork Mon Nov 18 23:42:28 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Saravana Kannan X-Patchwork-Id: 11250475 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2F2F6109A for ; Mon, 18 Nov 2019 23:42:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0DA8622304 for ; Mon, 18 Nov 2019 23:42:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="eLIHtQ5c" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726830AbfKRXmf (ORCPT ); Mon, 18 Nov 2019 18:42:35 -0500 Received: from mail-pl1-f202.google.com ([209.85.214.202]:45918 "EHLO mail-pl1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726809AbfKRXmf (ORCPT ); Mon, 18 Nov 2019 18:42:35 -0500 Received: by mail-pl1-f202.google.com with SMTP id f7so11986597plj.12 for ; Mon, 18 Nov 2019 15:42:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=0HR7354fwzZLoSsix3DSN5/aq9ZZkqFDIdkoEC/pg4Q=; b=eLIHtQ5cGODVB5oUClKGTxOm32S2L3VPlYuuJQy0HOf4Oecy2Eazi3odRqS8f+Gk1m PMOTqKF8xCcNqJysanPyICJC+k0lhf9Br26M+vCXz02RZBBLcMAHM0HJj4cN9vuASDks 3IlPLeAMK8tTLiygMX5F3EwDQNu7R4MhLRreq4QJKpRWwE0JrkKcZbw4HicZOUqL33hb RytiyzJvaja2Nni7oyTzsXjdEASIPNRKFRfrMhviC020dLwaaG9TWA5G/dCi6I5keRZU v3aeMDw+rM7eo+pOhNYWXWxsZ1lYe2xkJedMTNkmwXjTD0grPvzxGCZTcdT3uZcthtFd GCfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=0HR7354fwzZLoSsix3DSN5/aq9ZZkqFDIdkoEC/pg4Q=; b=B41/TOJhQm722Lw79TRIHIZblH0I6rTQvMOmUdss+XAWt1xFYYsLohJQCcNJeT50MJ lavJ9QqCyZvLh3mMp5s9kmyM1crj1Zrz/RQ8LqPSu2MOLt2tTyjUZl7uN3Wt+hKMCEv/ +RBmvM2nmwZHEPMEdWyLGmSA5Al/Ui4eaow9QAHfLxxFNekNCAEPgK08DPWNKj8THPCf jsHfH97NnZeoBEPA5Gp9RZ6y1h0Sf+fRLtpgXIDMCA/1S5x+H13KLcYW01Jg6oBrdOOH lyOhH4G3x7br+Cehklt6KIeyPJ8pvGmJTXNyO9K9S2ijLQ+IovLfEouiUu61ALXS0lzO Zuhw== X-Gm-Message-State: APjAAAV5W6wfDczvUDZ9R3gmktCGyS8l/sGShEt9y/izXuU0Q2krQToO 0FrdOBmyu+QMwrt8PE5Ff09FgfGY124L2D4= X-Google-Smtp-Source: APXvYqzwIk4iobTLY88s1QZ96OOGkhRDC6hNTVvwik6LaqYqTQYmEX70hUoCsiX+t+O0+E9UMBnv3z1Gnc0eNUo= X-Received: by 2002:a63:907:: with SMTP id 7mr2076044pgj.256.1574120554298; Mon, 18 Nov 2019 15:42:34 -0800 (PST) Date: Mon, 18 Nov 2019 15:42:28 -0800 Message-Id: <20191118234229.54085-1-saravanak@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.24.0.432.g9d3f5f5b63-goog Subject: [PATCH v1] clk: Keep boot clocks on for multiple consumers From: Saravana Kannan To: Michael Turquette , Stephen Boyd Cc: Saravana Kannan , kernel-team@android.com, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org Sender: linux-clk-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-clk@vger.kernel.org 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 --- 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;