linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
To: linux-amlogic@lists.infradead.org, linux-clk@vger.kernel.org,
	jbrunet@baylibre.com, narmstrong@baylibre.com
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, mturquette@baylibre.com,
	sboyd@kernel.org,
	Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Subject: [RFC v1 1/7] clk: meson: meson8b: run from the XTAL when changing the CPU frequency
Date: Wed, 14 Nov 2018 23:57:19 +0100	[thread overview]
Message-ID: <20181114225725.2821-2-martin.blumenstingl@googlemail.com> (raw)
In-Reply-To: <20181114225725.2821-1-martin.blumenstingl@googlemail.com>

Changing the CPU clock requires changing various clocks including the
SYS PLL. The existing meson clk-pll and clk-regmap drivers can change
all of the relevant clocks already.
However, changing for exampe the SYS PLL is problematic because as long
as the CPU is running off a clock derived from SYS PLL changing the
latter results in a full system lockup.
Fix this system lockup by switching the CPU clock to run off the XTAL
while we are changing the any of the clocks in the CPU clock tree.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
---
 drivers/clk/meson/meson8b.c | 63 +++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
index 9bd5920da0ff..40e77fe4ba7c 100644
--- a/drivers/clk/meson/meson8b.c
+++ b/drivers/clk/meson/meson8b.c
@@ -1103,6 +1103,53 @@ static const struct reset_control_ops meson8b_clk_reset_ops = {
 	.deassert = meson8b_clk_reset_deassert,
 };
 
+struct meson8b_nb_data {
+	struct notifier_block nb;
+	struct clk_hw_onecell_data *onecell_data;
+};
+
+static int meson8b_cpu_clk_notifier_cb(struct notifier_block *nb,
+				       unsigned long event, void *data)
+{
+	struct meson8b_nb_data *nb_data =
+		container_of(nb, struct meson8b_nb_data, nb);
+	struct clk_hw **hws = nb_data->onecell_data->hws;
+	struct clk_hw *cpu_clk_hw, *parent_clk_hw;
+	struct clk *cpu_clk, *parent_clk;
+	int ret;
+
+	switch (event) {
+	case PRE_RATE_CHANGE:
+		parent_clk_hw = hws[CLKID_XTAL];
+		break;
+
+	case POST_RATE_CHANGE:
+		parent_clk_hw = hws[CLKID_CPU_SCALE_OUT_SEL];
+		break;
+
+	default:
+		return NOTIFY_DONE;
+	}
+
+	cpu_clk_hw = hws[CLKID_CPUCLK];
+	cpu_clk = __clk_lookup(clk_hw_get_name(cpu_clk_hw));
+
+	parent_clk = __clk_lookup(clk_hw_get_name(parent_clk_hw));
+
+	ret = clk_set_parent(cpu_clk, parent_clk);
+	if (ret)
+		return notifier_from_errno(ret);
+
+	udelay(100);
+
+	return NOTIFY_OK;
+}
+
+static struct meson8b_nb_data meson8b_cpu_nb_data = {
+	.nb.notifier_call = meson8b_cpu_clk_notifier_cb,
+	.onecell_data = &meson8b_hw_onecell_data,
+};
+
 static const struct regmap_config clkc_regmap_config = {
 	.reg_bits       = 32,
 	.val_bits       = 32,
@@ -1112,6 +1159,8 @@ static const struct regmap_config clkc_regmap_config = {
 static void __init meson8b_clkc_init(struct device_node *np)
 {
 	struct meson8b_clk_reset *rstc;
+	const char *notifier_clk_name;
+	struct clk *notifier_clk;
 	void __iomem *clk_base;
 	struct regmap *map;
 	int i, ret;
@@ -1166,6 +1215,20 @@ static void __init meson8b_clkc_init(struct device_node *np)
 			return;
 	}
 
+	/*
+	 * FIXME we shouldn't program the muxes in notifier handlers. The
+	 * tricky programming sequence will be handled by the forthcoming
+	 * coordinated clock rates mechanism once that feature is released.
+	 */
+	notifier_clk_name = clk_hw_get_name(&meson8b_cpu_scale_out_sel.hw);
+	notifier_clk = __clk_lookup(notifier_clk_name);
+	ret = clk_notifier_register(notifier_clk, &meson8b_cpu_nb_data.nb);
+	if (ret) {
+		pr_err("%s: failed to register the CPU clock notifier\n",
+		       __func__);
+		return;
+	}
+
 	ret = of_clk_add_hw_provider(np, of_clk_hw_onecell_get,
 				     &meson8b_hw_onecell_data);
 	if (ret)
-- 
2.19.1


  reply	other threads:[~2018-11-14 22:58 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-14 22:57 [RFC v1 0/7] Meson8b: make the CPU clock mutable Martin Blumenstingl
2018-11-14 22:57 ` Martin Blumenstingl [this message]
2018-11-15  9:53   ` [RFC v1 1/7] clk: meson: meson8b: run from the XTAL when changing the CPU frequency Jerome Brunet
2018-11-14 22:57 ` [RFC v1 2/7] clk: meson: meson8b: do not use cpu_div3 for cpu_scale_out_sel Martin Blumenstingl
2018-11-15  9:42   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 3/7] clk: meson: clk-pll: check if the clock is already enabled Martin Blumenstingl
2018-11-15  9:14   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 4/7] clk: meson: clk-pll: add the is_enabled function in the clk_ops Martin Blumenstingl
2018-11-15  9:16   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 5/7] clk: meson: meson8b: mark the CPU clock as CLK_IS_CRITICAL Martin Blumenstingl
2018-11-15  9:46   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 6/7] clk: meson: meson8b: add support for more M/N values in sys_pll Martin Blumenstingl
2018-11-15  9:41   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 7/7] clk: meson: meson8b: allow changing the CPU clock tree Martin Blumenstingl
2018-11-15  9:46   ` Jerome Brunet
2018-11-15 10:08 ` [RFC v1 0/7] Meson8b: make the CPU clock mutable Neil Armstrong

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181114225725.2821-2-martin.blumenstingl@googlemail.com \
    --to=martin.blumenstingl@googlemail.com \
    --cc=jbrunet@baylibre.com \
    --cc=linux-amlogic@lists.infradead.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-clk@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mturquette@baylibre.com \
    --cc=narmstrong@baylibre.com \
    --cc=sboyd@kernel.org \
    --subject='Re: [RFC v1 1/7] clk: meson: meson8b: run from the XTAL when changing the CPU frequency' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).