[PATCH] drm/amd/pm: Prevent divide by zero

[Christian König]

Am 09.07.22 um 04:31 schrieb Mr. B34r:
> From: Vannoonnoo <mr.b34r at kolabnow.com>
>
> divide error: 0000 [#1] SMP PTI
> CPU: 3 PID: 78925 Comm: tee Not tainted 5.15.50-1-lts #1 5c320a339f0e397222fdfc9449eff04c0b12ea83
> Hardware name: MSI MS-7A59/Z270 SLI PLUS (MS-7A59), BIOS 1.90 01/30/2018
> RIP: 0010:smu_v11_0_set_fan_speed_rpm+0x11/0x110 [amdgpu]
>
> Speed is user-configurable through a file. I accidentally set it to zero, and the driver crashed.

Good catch, just some minor style problems. Your Signed-of-by line is 
missing for example.

There is a checkpath.pl script in the Linux kernel source which can 
point out such trivial mistakes.

Please run it on your patch and resend, apart from that looks good to me.

Christian.

>
> ---
>   drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c b/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c
> index 5f8809f6990d..69cebdb58c04 100644
> --- a/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c
> +++ b/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c
> @@ -1236,6 +1236,10 @@ int smu_v11_0_set_fan_speed_rpm(struct smu_context *smu,
>   	 * - For some Sienna Cichlid SKU, the fan speed cannot be set
>   	 *   lower than 500 RPM.
>   	 */
> +
> +	if (speed == 0)
> +		return -EINVAL;
> +
>   	tach_period = 60 * crystal_clock_freq * 10000 / (8 * speed);
>   	WREG32_SOC15(THM, 0, mmCG_TACH_CTRL,
>   		     REG_SET_FIELD(RREG32_SOC15(THM, 0, mmCG_TACH_CTRL),