Hi Paul, On 09/12/2012 12:28 AM, Paul Walmsley wrote: > Hi Kishon, Benoît, > > On Fri, 7 Sep 2012, Kishon Vijay Abraham I wrote: > >> Made *ocp2scp_usb_phy_phy_48m* as the main_clk for ocp2scp. Since this >> ocp2scp module does not have any fck but does have a single opt_clock, >> it is added as the main_clk for ocp2scp. Also removed phy_48m as the >> optional clock since it is now made as the main clock. By this the >> driver need not enable/disable phy_48m clk separately and >> runtime_get/runtime_put will take care of that. > > Looking at this patch, it doesn't seem to make sense from a hardware point > of view. If you look at the OMAP4430 TRM Rev. AE, Table 23-1166 "Clocks > and Resets", the 48MHz clock input is listed as an "Optional functional > clock". The main functional clock is listed as "INIT_960M_FCLK", which > according to the same TRM, Section 3.6.3.9.1 "Overview", is an alias for > the clock we call "dpll_usb_clkdcoldo_ck". > > So if any clock should be the main functional clock in the hwmod data, > shouldn't it be dpll_usb_clkdcoldo_ck? The goal with the hwmod data > is/was to have it match the hardware. In this case, the ocp2scp IP is just the *bus controller* to access the real USB_UTMI_PHY IP. The TRM diagram does not show that level of detail unfortunately. You can check the PRCM spec (Figure 78 : CD_L3_INIT_USB clock scheme) to see the two modules. So considering phy_48m as the main clock is still correct for the ocp2scp IP. The INIT_960M_FCLK will be a fck associated with the child of the ocp2scp nodes which is the usb_phy. Upgrading the opt_clk to fck does make sense as soon as we don't have any other functional clock and as soon as this clock is *mandatory*. The optional aspect in that case is just a wrong PRCM naming for a clock that is mandatory. It is similar to the DSS case that does have only optional clocks that are mandatory. I do agree that we must stick to the HW definition as far as we can. But the optional attribute is something that is wrong/inaccurate for a couple of IPs. HW folks agreed on that point and will fix that in the future. Regards, Benoit -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
