Re: [v5 2/2] pwm: Add Aspeed ast2600 PWM support
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From: Billy Tsai <billy_tsai@aspeedtech.com>
Date: 2021-05-17 02:53:50
Also in:
linux-aspeed, linux-devicetree, linux-pwm, lkml
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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel