[2/6] clk: bcm2835: add locking to pll*_on/off methods

Commit Message

Martin Sperl Feb. 29, 2016, 11:39 a.m. UTC

From: Martin Sperl <[e-mail]>

Add missing locking to:
* bcm2835_pll_divider_on
* bcm2835_pll_divider_off
to protect the read modify write cycle for the
register access protecting both cm_ctl and a2w_ctl
registers.

Fixes: 41691b8862e2 ("clk: bcm2835: Add support for programming the
audio domain clocks")

Signed-off-by: Martin Sperl <[e-mail]>
---
 drivers/clk/bcm/clk-bcm2835.c |    4 ++++
 1 file changed, 4 insertions(+)

--
1.7.10.4

Comments

Eric Anholt Feb. 29, 2016, 8:06 p.m. UTC | #1

[e-mail] writes:

> From: Martin Sperl <[e-mail]>
>
> Add missing locking to:
> * bcm2835_pll_divider_on
> * bcm2835_pll_divider_off
> to protect the read modify write cycle for the
> register access protecting both cm_ctl and a2w_ctl
> registers.

s/ctl/reg/ in the commit message

bcm2835_pll_divider_set_rate() also does an RMW on cm_reg, why was it
left out?

Since the a2w reg is only modified by _on and _off, and the core holds
the prepare lock across those, I think it was already safe and doesn't
need to be mentioned here.

Patch

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index 2b7c6af..30d6486 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -1088,10 +1088,12 @@  static void bcm2835_pll_divider_off(struct clk_hw *hw)
 	struct bcm2835_cprman *cprman = divider->cprman;
 	const struct bcm2835_pll_divider_data *data = divider->data;

+	spin_lock(&cprman->regs_lock);
 	cprman_write(cprman, data->cm_reg,
 		     (cprman_read(cprman, data->cm_reg) &
 		      ~data->load_mask) | data->hold_mask);
 	cprman_write(cprman, data->a2w_reg, A2W_PLL_CHANNEL_DISABLE);
+	spin_unlock(&cprman->regs_lock);
 }

 static int bcm2835_pll_divider_on(struct clk_hw *hw)
@@ -1100,12 +1102,14 @@  static int bcm2835_pll_divider_on(struct clk_hw *hw)
 	struct bcm2835_cprman *cprman = divider->cprman;
 	const struct bcm2835_pll_divider_data *data = divider->data;

+	spin_lock(&cprman->regs_lock);
 	cprman_write(cprman, data->a2w_reg,
 		     cprman_read(cprman, data->a2w_reg) &
 		     ~A2W_PLL_CHANNEL_DISABLE);

 	cprman_write(cprman, data->cm_reg,
 		     cprman_read(cprman, data->cm_reg) & ~data->hold_mask);
+	spin_unlock(&cprman->regs_lock);

 	return 0;
 }