Patch "clk-divider: make sure read-only dividers do not write to their register" has been added to the 4.5-stable tree

Patch "clk-divider: make sure read-only dividers do not write to their register" has been added to the 4.5-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    clk-divider: make sure read-only dividers do not write to their register

to the 4.5-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     clk-divider-make-sure-read-only-dividers-do-not-write-to-their-register.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 50359819794b4a16ae35051cd80f2dab025f6019 Mon Sep 17 00:00:00 2001
From: Heiko Stuebner <heiko@sntech.de>
Date: Thu, 21 Jan 2016 21:53:09 +0100
Subject: clk-divider: make sure read-only dividers do not write to their register

From: Heiko Stuebner <heiko@sntech.de>

commit 50359819794b4a16ae35051cd80f2dab025f6019 upstream.

Commit e6d5e7d90be9 ("clk-divider: Fix READ_ONLY when divider > 1") removed
the special ops struct for read-only clocks and instead opted to handle
them inside the regular ops.

On the rk3368 this results in breakage as aclkm now gets set a value.
While it is the same divider value, the A53 core still doesn't like it,
which can result in the cpu ending up in a hang.
The reason being that "ACLKENMasserts one clock cycle before the rising
edge of ACLKM" and the clock should only be touched when STANDBYWFIL2
is asserted.

To fix this, reintroduce the read-only ops but do include the round_rate
callback. That way no writes that may be unsafe are done to the divider
register in any case.

The Rockchip use of the clk_divider_ops is adapted to this split again,
as is the nxp, lpc18xx-ccu driver that was included since the original
commit. On lpc18xx-ccu the divider seems to always be read-only
so only uses the new ops now.

Fixes: e6d5e7d90be9 ("clk-divider: Fix READ_ONLY when divider > 1")
Reported-by: Zhang Qing <zhangqing@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/clk/clk-divider.c         |   11 ++++++++++-
 drivers/clk/nxp/clk-lpc18xx-ccu.c |    2 +-
 drivers/clk/rockchip/clk.c        |    4 +++-
 include/linux/clk-provider.h      |    1 +
 4 files changed, 15 insertions(+), 3 deletions(-)

--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -423,6 +423,12 @@ const struct clk_ops clk_divider_ops = {
 };
 EXPORT_SYMBOL_GPL(clk_divider_ops);
 
+const struct clk_ops clk_divider_ro_ops = {
+	.recalc_rate = clk_divider_recalc_rate,
+	.round_rate = clk_divider_round_rate,
+};
+EXPORT_SYMBOL_GPL(clk_divider_ro_ops);
+
 static struct clk *_register_divider(struct device *dev, const char *name,
 		const char *parent_name, unsigned long flags,
 		void __iomem *reg, u8 shift, u8 width,
@@ -446,7 +452,10 @@ static struct clk *_register_divider(str
 		return ERR_PTR(-ENOMEM);
 
 	init.name = name;
-	init.ops = &clk_divider_ops;
+	if (clk_divider_flags & CLK_DIVIDER_READ_ONLY)
+		init.ops = &clk_divider_ro_ops;
+	else
+		init.ops = &clk_divider_ops;
 	init.flags = flags | CLK_IS_BASIC;
 	init.parent_names = (parent_name ? &parent_name: NULL);
 	init.num_parents = (parent_name ? 1 : 0);
--- a/drivers/clk/nxp/clk-lpc18xx-ccu.c
+++ b/drivers/clk/nxp/clk-lpc18xx-ccu.c
@@ -222,7 +222,7 @@ static void lpc18xx_ccu_register_branch_
 		div->width = 1;
 
 		div_hw = &div->hw;
-		div_ops = &clk_divider_ops;
+		div_ops = &clk_divider_ro_ops;
 	}
 
 	branch->gate.reg = branch->offset + reg_base;
--- a/drivers/clk/rockchip/clk.c
+++ b/drivers/clk/rockchip/clk.c
@@ -90,7 +90,9 @@ static struct clk *rockchip_clk_register
 		div->width = div_width;
 		div->lock = lock;
 		div->table = div_table;
-		div_ops = &clk_divider_ops;
+		div_ops = (div_flags & CLK_DIVIDER_READ_ONLY)
+						? &clk_divider_ro_ops
+						: &clk_divider_ops;
 	}
 
 	clk = clk_register_composite(NULL, name, parent_names, num_parents,
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -385,6 +385,7 @@ struct clk_divider {
 #define CLK_DIVIDER_MAX_AT_ZERO		BIT(6)
 
 extern const struct clk_ops clk_divider_ops;
+extern const struct clk_ops clk_divider_ro_ops;
 
 unsigned long divider_recalc_rate(struct clk_hw *hw, unsigned long parent_rate,
 		unsigned int val, const struct clk_div_table *table,


Patches currently in stable-queue which might be from heiko@sntech.de are

queue-4.5/clk-rockchip-fix-wrong-mmc-phase-shift-for-rk3228.patch
queue-4.5/clk-rockchip-free-memory-in-error-cases-when-registering-clock-branches.patch
queue-4.5/clk-divider-make-sure-read-only-dividers-do-not-write-to-their-register.patch
queue-4.5/soc-rockchip-power-domain-fix-err-handle-while-probing.patch