Hi On Thu, 22 Sep 2011, Cousson, Benoit wrote: > ADDR_TYPE_RT is mainly use for sysconfig access inside hwmod core today, so > why should we use it in this case? Just for consistency, since the flag isn't defined to be SYSCONFIG-specific. That way, if there's another need -- other than SYSCONFIG access -- to identify the chunk of address space that's used for register access, we won't have to dig through and possibly repatch the hwmod data, just because some people didn't want to follow the rule. If the flag was simply defined to be SYSCONFIG-specific, then you're right, it wouldn't be needed. > To be honest, I've been confused with that flag for some time :-) > * ADDR_TYPE_RT: Address space contains module register target data. > Maybe that's my English, but what does "register target data" mean exactly? The name comes from the L3 section of the 34xx TRM - see for example section 9.1.1 "Terminology" of the rev ZR TRM. The L3 has several address space sections, and whoever wrote that text -- Sonics? -- called the one with the L3's own internal registers the "register target." And I was looking for a name that I did not have to make up, so I personally wouldn't have to defend the name ;-) > What was the intent? Providing a way to identify some register vs memory > space? As you suggest, the original impetus for the flag was to identify which chunk of address space needs to be mapped by the hwmod code for SYSCONFIG accesses to work. On current OMAPs, this seems to be the same thing as identifying the IP block's primary register area for every module with SYS* and REVISION registers. And I probably thought at the time that specifying the IP block's main register mapping seemed more useful and generally applicable than designating where the SYSCONFIG register was. Hence the current definition. > Regarding main_clk, I do not think that some internal IPs like ohci/ehci > should have a main_clk, since this is not visible at that level. Do you not agree that every IP block that contains sequential logic on current and foreseeable future SoCs must have some clock signal to drive that logic? The idea of the main_clk was not intended to be PRCM or OCP or even OMAP-specific. It's just intended to represent a clock that is used to drive the register logic inside the IP block. Therefore it must be enabled before any register access may occur. Even if clock gating is handled by some higher-level interface (e.g., at the IP block level), the main_clk has a rate, so it also implies an upper limit on how quickly register operations can occur. I suppose that all of the IP block's clocks could be "optional clocks," but we know that every IP block with registers requires at least one clock to work, and that should be the main_clk. > These blocks do not have any PRCM / OCP connection. In fact they should > not even be hwmod in theory, these are just some internal IPs inside the > usb_host controller. After looking at the OMAP USB host controller drivers, particularly drivers/mfd/omap-usb-host.c, I completely agree: it's not just theory: OMAP shouldn't have EHCI and OHCI hwmods in practice, either :-) > These are hwmods just because of the dynamic mux support needed by these > IPs. That was one of the comments I made on these, and Keshava explained > me the rational and added it in the changelog. On OMAP, since the EHCI and OHCI IP blocks are integrated into the UHH IP block, an MFD driver creates the EHCI and OHCI platform_devices (see drivers/mfd/omap-usb-host.c:omap_usbhs_alloc_children()). On OMAP, the EHCI and OHCI aren't hwmod-backed devices, and so they shouldn't be using the hwmod dynamic pin remuxing code directly. So I'd suggest one of two approaches: 1. If the pin muxing can follow the PM runtime status of the UHH IP block, then the pin mux data should be associated with the UHH hwmod. 2. If the pin muxing must follow the EHCI/OHCI IP block PM runtime status, then drivers/mfd/omap-usb-host.c is what should be handling the remuxing. omap-usb-host.c can set the dev_pm_ops of the EHCI/OHCI platform_devices to point to functions either in arch/arm/mach-omap2/usb-host.c, or local functions that call into mach-omap2/usb-host.c functions to handle pin remuxing. (Those function pointers should be provided to the MFD driver in some clean way, like via platform_data.) > Hopefully, we will not have that limitation once we will have migrated > that to DT :-) Even if the data is coming from some other source, if the code still relies on main_clk, then it will need to be present. But why do you perceive that specifying a main_clk is a limitation? Or, put differently: what problem is caused by specifying a main_clk here? - Paul -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
