[PATCH/RFT] clk: shmobile: div6: Fix .recalc_rate() using a stale divisor

[PATCH/RFT] clk: shmobile: div6: Fix .recalc_rate() using a stale divisor

[Geert Uytterhoeven]

cpg_div6_clock_set_rate() only programs the new divisor if the clock
isn't stopped. If the clock is stopped, it will update the cached
divisor value only, which will be programmed into the clock registers
when enabling the clock later.

However, cpg_div6_clock_recalc_rate() reads the divisor from the clock
registers instead of using the cached value, leading to an incorrect
result if the clock is currently stopped.

Make cpg_div6_clock_recalc_rate() use the cached value to fix this.

Reported-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>
Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
Ramesh: Can you please give this a try? Thanks!
---
 drivers/clk/shmobile/clk-div6.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/clk/shmobile/clk-div6.c b/drivers/clk/shmobile/clk-div6.c
index 9999947694509d58..0627860233cbf97e 100644
--- a/drivers/clk/shmobile/clk-div6.c
+++ b/drivers/clk/shmobile/clk-div6.c
@@ -82,9 +82,8 @@ static unsigned long cpg_div6_clock_recalc_rate(struct clk_hw *hw,
 						unsigned long parent_rate)
 {
 	struct div6_clock *clock = to_div6_clock(hw);
-	unsigned int div = (clk_readl(clock->reg) & CPG_DIV6_DIV_MASK) + 1;
 
-	return parent_rate / div;
+	return parent_rate / clock->div;
 }
 
 static unsigned int cpg_div6_clock_calc_div(unsigned long rate,
-- 
1.9.1

Re: [PATCH/RFT] clk: shmobile: div6: Fix .recalc_rate() using a stale divisor

[Laurent Pinchart]

Hi Geert,

Thank you for the patch.

On Thursday 18 February 2016 15:30:12 Geert Uytterhoeven wrote:
> cpg_div6_clock_set_rate() only programs the new divisor if the clock
> isn't stopped. If the clock is stopped, it will update the cached
> divisor value only, which will be programmed into the clock registers
> when enabling the clock later.
> 
> However, cpg_div6_clock_recalc_rate() reads the divisor from the clock
> registers instead of using the cached value, leading to an incorrect
> result if the clock is currently stopped.
> 
> Make cpg_div6_clock_recalc_rate() use the cached value to fix this.
> 
> Reported-by: Ramesh Shanmugasundaram
> <ramesh.shanmugasundaram@bp.renesas.com>
> Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
> Ramesh: Can you please give this a try? Thanks!
> ---
>  drivers/clk/shmobile/clk-div6.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/shmobile/clk-div6.c
> b/drivers/clk/shmobile/clk-div6.c index 9999947694509d58..0627860233cbf97e
> 100644
> --- a/drivers/clk/shmobile/clk-div6.c
> +++ b/drivers/clk/shmobile/clk-div6.c
> @@ -82,9 +82,8 @@ static unsigned long cpg_div6_clock_recalc_rate(struct
> clk_hw *hw, unsigned long parent_rate)
>  {
>  	struct div6_clock *clock = to_div6_clock(hw);
> -	unsigned int div = (clk_readl(clock->reg) & CPG_DIV6_DIV_MASK) + 1;
> 
> -	return parent_rate / div;
> +	return parent_rate / clock->div;
>  }
> 
>  static unsigned int cpg_div6_clock_calc_div(unsigned long rate,

-- 
Regards,

Laurent Pinchart

RE: [PATCH/RFT] clk: shmobile: div6: Fix .recalc_rate() using a stale divisor

[Ramesh Shanmugasundaram]

Hi Geert,

Thanks for the patch.

> From: Geert Uytterhoeven [mailto:geert+renesas@glider.be]
> Sent: 18 February 2016 14:30
>
> cpg_div6_clock_set_rate() only programs the new divisor if the clock isn'=
t
> stopped. If the clock is stopped, it will update the cached divisor value
> only, which will be programmed into the clock registers when enabling the
> clock later.
>
> However, cpg_div6_clock_recalc_rate() reads the divisor from the clock
> registers instead of using the cached value, leading to an incorrect
> result if the clock is currently stopped.
>
> Make cpg_div6_clock_recalc_rate() use the cached value to fix this.
>
> Reported-by: Ramesh Shanmugasundaram
> <ramesh.shanmugasundaram@bp.renesas.com>
> Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> Ramesh: Can you please give this a try? Thanks!

Tested-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>

> ---
>  drivers/clk/shmobile/clk-div6.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/clk/shmobile/clk-div6.c b/drivers/clk/shmobile/clk-
> div6.c index 9999947694509d58..0627860233cbf97e 100644
> --- a/drivers/clk/shmobile/clk-div6.c
> +++ b/drivers/clk/shmobile/clk-div6.c
> @@ -82,9 +82,8 @@ static unsigned long cpg_div6_clock_recalc_rate(struct
> clk_hw *hw,
>  unsigned long parent_rate)
>  {
>  struct div6_clock *clock =3D to_div6_clock(hw);
> -unsigned int div =3D (clk_readl(clock->reg) & CPG_DIV6_DIV_MASK) + 1;
>
> -return parent_rate / div;
> +return parent_rate / clock->div;
>  }
>
>  static unsigned int cpg_div6_clock_calc_div(unsigned long rate,
> --
> 1.9.1

Thanks,
Ramesh



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