From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe Kleine-König Date: Fri, 9 Jul 2021 07:53:25 +0200 Subject: [v8 2/2] pwm: Add Aspeed ast2600 PWM support In-Reply-To: References: <20210608064658.14262-1-billy_tsai@aspeedtech.com> <20210608064658.14262-3-billy_tsai@aspeedtech.com> <20210702143147.6a7psfup4tlidq2x@pengutronix.de> Message-ID: <20210709055325.4y4ufjvoiwo2pcvi@pengutronix.de> List-Id: To: linux-aspeed@lists.ozlabs.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hello Billy, On Fri, Jul 09, 2021 at 05:40:45AM +0000, Billy Tsai wrote: > On 2021/7/2, 10:32 PM, "Uwe Kleine-K?nig" wrote: > > The multiplication can be up to: > > > 100000000 * (1 << 31) * (31 + 1) * (255 + 1) > > > right? This needs 71 bits and so might overflow a u64. > > No, the multiplication can be up to: > > Max(div_h) = 15 > Max(div_l) = 255 > Max(clk_period) = 255 > 1000000000 * (1 << 15) * (255 + 1) * (255 + 1) < 2^64 - 1 > it doesn't overflow a u64. Ah, you're right. Please note this in a comment (not that you were right, but that it doesn't overflow :-) Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | https://www.pengutronix.de/ | -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 488 bytes Desc: not available URL: