[PATCH] pwm: rcar: Use div64_ul instead of do_div

[PATCH] pwm: rcar: Use div64_ul instead of do_div

[cgel.zte]

From: Changcheng Deng <deng.changcheng@zte.com.cn>

do_div() does a 64-by-32 division. If the divisor is unsigned long, using
div64_ul can avoid truncation to 32-bit.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
---
 drivers/pwm/pwm-rcar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
index b437192380e2..fb475c188e1e 100644
--- a/drivers/pwm/pwm-rcar.c
+++ b/drivers/pwm/pwm-rcar.c
@@ -111,7 +111,7 @@ static int rcar_pwm_set_counter(struct rcar_pwm_chip *rp, int div, int duty_ns,
 	u32 cyc, ph;
 
 	one_cycle = (unsigned long long)NSEC_PER_SEC * 100ULL * (1 << div);
-	do_div(one_cycle, clk_rate);
+	div64_ul(one_cycle, clk_rate);
 
 	tmp = period_ns * 100ULL;
 	do_div(tmp, one_cycle);
-- 
2.25.1

Re: [PATCH] pwm: rcar: Use div64_ul instead of do_div

[Uwe Kleine-König]

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On Wed, Nov 17, 2021 at 02:08:54AM +0000, cgel.zte@gmail.com wrote:
> From: Changcheng Deng <deng.changcheng@zte.com.cn>
> 
> do_div() does a 64-by-32 division. If the divisor is unsigned long, using
> div64_ul can avoid truncation to 32-bit.
> 
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
> ---
>  drivers/pwm/pwm-rcar.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
> index b437192380e2..fb475c188e1e 100644
> --- a/drivers/pwm/pwm-rcar.c
> +++ b/drivers/pwm/pwm-rcar.c
> @@ -111,7 +111,7 @@ static int rcar_pwm_set_counter(struct rcar_pwm_chip *rp, int div, int duty_ns,
>  	u32 cyc, ph;
>  
>  	one_cycle = (unsigned long long)NSEC_PER_SEC * 100ULL * (1 << div);
> -	do_div(one_cycle, clk_rate);
> +	div64_ul(one_cycle, clk_rate);

Same problem as with the atmel-hlcdc patch: The calling convention of
do_div and div64_ul are different and with the proposed patch the result
of the division is unused.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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[PATCH V2] pwm: rcar: Use div64_ul instead of do_div

[cgel.zte]

From: Changcheng Deng <deng.changcheng@zte.com.cn>

do_div() does a 64-by-32 division. If the divisor is unsigned long, using
div64_ul can avoid truncation to 32-bit.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
---
 drivers/pwm/pwm-rcar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
index b437192380e2..fb475c188e1e 100644
--- a/drivers/pwm/pwm-rcar.c
+++ b/drivers/pwm/pwm-rcar.c
@@ -111,7 +111,7 @@ static int rcar_pwm_set_counter(struct rcar_pwm_chip *rp, int div, int duty_ns,
 	u32 cyc, ph;
 
 	one_cycle = (unsigned long long)NSEC_PER_SEC * 100ULL * (1 << div);
-	do_div(one_cycle, clk_rate);
+	one_cycle = div64_ul(one_cycle, clk_rate);
 
 	tmp = period_ns * 100ULL;
 	do_div(tmp, one_cycle);
-- 
2.25.1

[PATCH V3] pwm: rcar: Use div64_ul instead of do_div

[cgel.zte]

From: Changcheng Deng <deng.changcheng@zte.com.cn>

do_div() does a 64-by-32 division. Here the divisor is an unsigned long
which on some platforms is 64 bit wide. So use div64_ul instead of do_div
to avoid a possible truncation.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
---
 drivers/pwm/pwm-rcar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
index b437192380e2..fb475c188e1e 100644
--- a/drivers/pwm/pwm-rcar.c
+++ b/drivers/pwm/pwm-rcar.c
@@ -111,7 +111,7 @@ static int rcar_pwm_set_counter(struct rcar_pwm_chip *rp, int div, int duty_ns,
 	u32 cyc, ph;
 
 	one_cycle = (unsigned long long)NSEC_PER_SEC * 100ULL * (1 << div);
-	do_div(one_cycle, clk_rate);
+	one_cycle = div64_ul(one_cycle, clk_rate);
 
 	tmp = period_ns * 100ULL;
 	do_div(tmp, one_cycle);
-- 
2.25.1

Re: [PATCH V3] pwm: rcar: Use div64_ul instead of do_div

[Uwe Kleine-König]

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On Thu, Nov 18, 2021 at 03:02:15AM +0000, cgel.zte@gmail.com wrote:
> From: Changcheng Deng <deng.changcheng@zte.com.cn>
> 
> do_div() does a 64-by-32 division. Here the divisor is an unsigned long
> which on some platforms is 64 bit wide. So use div64_ul instead of do_div
> to avoid a possible truncation.
> 
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>

You're supposed to add a S-o-b line for yourself with a email address
that matches the sender of the patch.

Other than that the patch looks fine now.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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