Hi Felipe On Fri, 11 Nov 2011, Felipe Balbi wrote: > I have a doubt about using clk API to change CLKSEL_UTMI_P1 bit for a > silicon errata (OMAP4460 i693) implementation. > > According to errata, I need to switch from external to internal clock > during USB port suspend, wait 1ms and switch back from internal to > external. > > How can I do that with clk API ? Is it by changing clk parent ? Any tips > would be helpful ;-) thanks clk_set_parent() is the way to go. There are 44xx struct clks that references CLKSEL_UTMI_P1 and CLKSEL_UTMI_P2: see utmi_p1_gfclk and utmi_p2_gfclk in mach-omap2/clock44xx_data.c. The possible parent clocks are listed in utmi_p1_gfclk_sel and utmi_p2_gfclk_sel in the same file. So you should be able to clk_get() the possible parent clocks and utmi_p1_gfclk during module init, then use clk_set_parent() to switch between them. For example, for port 1: new_parent = clk_set_parent(utmi_p1_clk, init_60m_clk); /* test new_parent for error */ /* delay 1ms */ new_parent = clk_set_parent(utmi_p1_clk, xclk60mhsp1_ck); or something similar. Please let me know if something like the above turns out not to work for you. One comment. Erratum i693 in SWPZ017A Public is not 100% explicit on whether the new parent clock needs to be enabled before the clk_set_parent() executes. It seems to imply that it does need to be enabled first. If so, this is contrary to what we previously believed was a safe sequence based on Richard Woodruff's post here: http://lkml.org/lkml/2009/2/19/416 The concern is that the parent-switching process may not be glitch-free. Of course, if it isn't, we're in trouble, because we may not be able to shut off a clock like init_60m_clk if the other port is using it. Perhaps it would be enough to gate the downstream clock node (e.g. usb_host_hs_utmi_p1_clk). We'll need to get some clarification on this. - Paul -- 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
