Messages in this thread |  | | From | Billy Tsai <> | Subject | Re: [v5 2/2] pwm: Add Aspeed ast2600 PWM support | Date | Mon, 17 May 2021 02:53:44 +0000 |
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Hello,
On 2021/5/15, 11:57 PM,Uwe Kleine-Königwrote:
> > + div_h = DIV_ROUND_DOWN_ULL(div_h, > > + (FIELD_MAX(PWM_ASPEED_CTRL_CLK_DIV_L) + 1)); > > + div_h = DIV_ROUND_DOWN_ULL(div_h, NSEC_PER_SEC);
> As a division is an expensive operation you can better first multiply > NSEC_PER_SEC and FIELD_MAX(PWM_ASPEED_CTRL_CLK_DIV_L) + 1 and divide by > the result.
When I multiply NSEC_PER_SEC and FIELD_MAX(PWM_ASPEED_CTRL_CLK_DIV_L) + 1 the result will overflow for 32-bits and the divisor type of do_div is 32-bits so I need to do div twice to avoid the issue. Can you give me some suggests?
Thanks
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