From patchwork Tue Jul 26 07:04:29 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chen-Yu Tsai X-Patchwork-Id: 9247751 X-Patchwork-Delegate: sboyd@codeaurora.org Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 6A2C560868 for ; Tue, 26 Jul 2016 07:07:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5BF572621E for ; Tue, 26 Jul 2016 07:07:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5079A26A4D; Tue, 26 Jul 2016 07:07:02 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F1F93269B2 for ; Tue, 26 Jul 2016 07:07:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755704AbcGZHFq (ORCPT ); Tue, 26 Jul 2016 03:05:46 -0400 Received: from mirror2.csie.ntu.edu.tw ([140.112.30.76]:52032 "EHLO wens.csie.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755310AbcGZHEm (ORCPT ); Tue, 26 Jul 2016 03:04:42 -0400 Received: by wens.csie.org (Postfix, from userid 1000) id E361A5F99F; Tue, 26 Jul 2016 15:04:34 +0800 (CST) From: Chen-Yu Tsai To: Michael Turquette , Stephen Boyd , Rob Herring , Mark Rutland , Maxime Ripard Cc: dev@linux-sunxi.org, Chen-Yu Tsai , linux-clk@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH 7/9] clk: sunxi-ng: mux: Add clk notifier functions Date: Tue, 26 Jul 2016 15:04:29 +0800 Message-Id: <1469516671-19377-8-git-send-email-wens@csie.org> X-Mailer: git-send-email 2.8.1 In-Reply-To: <1469516671-19377-1-git-send-email-wens@csie.org> References: <1469516671-19377-1-git-send-email-wens@csie.org> Sender: linux-clk-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-clk@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On sunxi we support cpufreq by changing the clock rate of PLL-CPU. It's possible the clock output of the PLL goes out of the CPU's operational limits when the PLL's multipliers / dividers are changed and it hasn't stabilized yet. This would result in the CPU hanging. To circumvent this, we temporarily switch the CPU mux clock to another stable clock before the rate change, and switch it back after the PLL stabilizes. This is done with clk notifiers registered on the PLL. This patch adds common functions for notifiers to reparent mux clocks. Signed-off-by: Chen-Yu Tsai --- drivers/clk/sunxi-ng/ccu_mux.c | 36 ++++++++++++++++++++++++++++++++++++ drivers/clk/sunxi-ng/ccu_mux.h | 14 ++++++++++++++ 2 files changed, 50 insertions(+) diff --git a/drivers/clk/sunxi-ng/ccu_mux.c b/drivers/clk/sunxi-ng/ccu_mux.c index f96eabb5d1f3..8a6e9065cb85 100644 --- a/drivers/clk/sunxi-ng/ccu_mux.c +++ b/drivers/clk/sunxi-ng/ccu_mux.c @@ -8,7 +8,9 @@ * the License, or (at your option) any later version. */ +#include #include +#include #include "ccu_gate.h" #include "ccu_mux.h" @@ -199,3 +201,37 @@ const struct clk_ops ccu_mux_ops = { .determine_rate = __clk_mux_determine_rate, .recalc_rate = ccu_mux_recalc_rate, }; + +/* + * This clock notifier is called when the frequency of the of the parent + * PLL clock is to be changed. The idea is to switch the parent to a + * stable clock, such as the main oscillator, while the PLL frequency + * stabilizes. + */ +static int ccu_mux_notifier_cb(struct notifier_block *nb, + unsigned long event, void *data) +{ + struct ccu_mux_nb *mux = to_ccu_mux_nb(nb); + int ret = 0; + + if (event == PRE_RATE_CHANGE) { + mux->original_index = ccu_mux_helper_get_parent(mux->common, + mux->cm); + ret = ccu_mux_helper_set_parent(mux->common, mux->cm, + mux->bypass_index); + } else if (event == POST_RATE_CHANGE) { + ret = ccu_mux_helper_set_parent(mux->common, mux->cm, + mux->original_index); + } + + udelay(mux->delay_us); + + return notifier_from_errno(ret); +} + +int ccu_mux_notifier_register(struct clk *clk, struct ccu_mux_nb *mux_nb) +{ + mux_nb->clk_nb.notifier_call = ccu_mux_notifier_cb; + + return clk_notifier_register(clk, &mux_nb->clk_nb); +} diff --git a/drivers/clk/sunxi-ng/ccu_mux.h b/drivers/clk/sunxi-ng/ccu_mux.h index 28d16ec18d55..7ddd9b2c6dbc 100644 --- a/drivers/clk/sunxi-ng/ccu_mux.h +++ b/drivers/clk/sunxi-ng/ccu_mux.h @@ -98,4 +98,18 @@ int ccu_mux_helper_set_parent(struct ccu_common *common, struct ccu_mux_internal *cm, u8 index); +struct ccu_mux_nb { + struct notifier_block clk_nb; + struct ccu_common *common; + struct ccu_mux_internal *cm; + + u32 delay_us; /* How many us to wait after reparenting */ + u8 bypass_index; /* Which parent to temporarily use */ + u8 original_index; /* This is set by the notifier callback */ +}; + +#define to_ccu_mux_nb(_nb) container_of(_nb, struct ccu_mux_nb, clk_nb) + +int ccu_mux_notifier_register(struct clk *clk, struct ccu_mux_nb *mux_nb); + #endif /* _CCU_MUX_H_ */