2020-07-17 17:09:38

by Scott Branden

Subject: [PATCH] pwm: bcm-iproc: handle clk_get_rate() return

From: Rayagonda Kokatanur <[email protected]>

Handle clk_get_rate() returning <= 0 condition to avoid
possible division by zero.

Fixes: daa5abc41c80 ("pwm: Add support for Broadcom iProc PWM controller")
Signed-off-by: Rayagonda Kokatanur <[email protected]>
Signed-off-by: Scott Branden <[email protected]>
---
drivers/pwm/pwm-bcm-iproc.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/pwm/pwm-bcm-iproc.c b/drivers/pwm/pwm-bcm-iproc.c
index 1f829edd8ee7..72a8607b6c8d 100644
--- a/drivers/pwm/pwm-bcm-iproc.c
+++ b/drivers/pwm/pwm-bcm-iproc.c
@@ -86,6 +86,11 @@ static void iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
u32 value, prescale;

rate = clk_get_rate(ip->clk);
+ if (rate == 0) {
+ state->period = 0;
+ state->duty_cycle = 0;
+ return;
+ }

value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);

--
2.17.1

2020-07-17 17:23:40

by Ray Jui

Subject: Re: [PATCH] pwm: bcm-iproc: handle clk_get_rate() return

On 7/17/2020 10:07 AM, Scott Branden wrote:
> From: Rayagonda Kokatanur <[email protected]>
>
> Handle clk_get_rate() returning <= 0 condition to avoid
> possible division by zero.
>
> Fixes: daa5abc41c80 ("pwm: Add support for Broadcom iProc PWM controller")
> Signed-off-by: Rayagonda Kokatanur <[email protected]>
> Signed-off-by: Scott Branden <[email protected]>
> ---
> drivers/pwm/pwm-bcm-iproc.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/pwm/pwm-bcm-iproc.c b/drivers/pwm/pwm-bcm-iproc.c
> index 1f829edd8ee7..72a8607b6c8d 100644
> --- a/drivers/pwm/pwm-bcm-iproc.c
> +++ b/drivers/pwm/pwm-bcm-iproc.c
> @@ -86,6 +86,11 @@ static void iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> u32 value, prescale;
>
> rate = clk_get_rate(ip->clk);
> + if (rate == 0) {
> + state->period = 0;
> + state->duty_cycle = 0;
> + return;
> + }

Based on the pwm core code, 'get_state' expects the following fields to
be populated: 'polarity', 'enabled', 'period', and 'duty cycle'.

The above logic will leave 'polarity' and 'enabled' completely
unpopulated when clock rate is zero.

>
> value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
>
>

2020-07-17 18:25:24

by Scott Branden

Subject: Re: [PATCH] pwm: bcm-iproc: handle clk_get_rate() return

On 2020-07-17 10:22 a.m., Ray Jui wrote:
>
> On 7/17/2020 10:07 AM, Scott Branden wrote:
>> From: Rayagonda Kokatanur <[email protected]>
>>
>> Handle clk_get_rate() returning <= 0 condition to avoid
>> possible division by zero.
>>
>> Fixes: daa5abc41c80 ("pwm: Add support for Broadcom iProc PWM controller")
>> Signed-off-by: Rayagonda Kokatanur <[email protected]>
>> Signed-off-by: Scott Branden <[email protected]>
>> ---
>> drivers/pwm/pwm-bcm-iproc.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/pwm/pwm-bcm-iproc.c b/drivers/pwm/pwm-bcm-iproc.c
>> index 1f829edd8ee7..72a8607b6c8d 100644
>> --- a/drivers/pwm/pwm-bcm-iproc.c
>> +++ b/drivers/pwm/pwm-bcm-iproc.c
>> @@ -86,6 +86,11 @@ static void iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
>> u32 value, prescale;
>>
>> rate = clk_get_rate(ip->clk);
>> + if (rate == 0) {
>> + state->period = 0;
>> + state->duty_cycle = 0;
>> + return;
>> + }
I'll move the logic after the polarity and enabled fields are populated.
> Based on the pwm core code, 'get_state' expects the following fields to
> be populated: 'polarity', 'enabled', 'period', and 'duty cycle'.
>
> The above logic will leave 'polarity' and 'enabled' completely
> unpopulated when clock rate is zero.
>
>>
>> value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
>>
>>