Hello Andrew, > From: Andrew Lunn, Sent: Monday, September 25, 2023 11:18 PM > > On Mon, Sep 25, 2023 at 09:34:16AM +0900, Yoshihiro Shimoda wrote: > > From: Tam Nguyen <tam.nguyen.xa@xxxxxxxxxxx> > > > > Fix the MPIC.PSMCS value following the programming example in the > > section 6.4.2 Management Data Clock (MDC) Setting, Ethernet MAC IP, > > S4 Hardware User Manual Rev.1.00. > > > > The value is calculated by > > MPIC.PSMCS = clk[MHz] / ((MDC frequency[MHz] + 1) * 2) > > with the input clock frequency of 320MHz and MDC frequency of 2.5MHz. > > Otherwise, this driver cannot communicate PHYs on the R-Car S4 Starter > > Kit board. > > If you run this calculation backwards, what frequency does > MPIC_PSMCS(0x3f) map to? Thank you for your review! I completely misunderstood the formula. In other words, the formula cannot calculate backwards. The correct formula is: MPIC.PSMCS = clk[MHz] / (MDC frequency[MHz] * 2) - 1 > Is 320MHz really fixed? For all silicon variants? Is it possible to do > a clk_get_rate() on a clock to get the actual clock rate? 320MHz is really fixed on the current existing all silicon variants. Yes, it is possible to do a clk_get_rate() on a clock to get the actual clock rate. So, I'll use clk_get_rate() on v2. Best regards, Yoshihiro Shimoda > Andrew
