On Mon, Mar 04, 2013 at 09:55:44AM -0700, Stephen Warren wrote: > On 03/04/2013 12:55 AM, Venu Byravarasu wrote: > > Stephen Warren wrote at Thursday, February 28, 2013 11:47 PM: > >> On 02/27/2013 11:36 PM, Venu Byravarasu wrote: > >>> To clear any configurations made by U-Boot on Tegra USB controller, > >>> reset it before init in probe. > >> > >>> diff --git a/drivers/usb/host/ehci-tegra.c b/drivers/usb/host/ehci-tegra.c > >> > >>> @@ -691,6 +692,10 @@ static int tegra_ehci_probe(struct platform_device > >> *pdev) > >>> if (err) > >>> goto fail_clk; > >>> > >>> + tegra_periph_reset_assert(tegra->clk); > >>> + udelay(1); > >>> + tegra_periph_reset_deassert(tegra->clk); > >> > >> I think this patch might cause unintended consequences. > >> > >> When the Tegra PHY code is converted to a driver (i.e. has its own > >> probe), the initial order of execution of the PHY and EHCI driver probes > >> will not be guaranteed. > >> > >> In particular, since the EHCI probe will attempt to "find" the PHY > >> device, and defer the EHCI probe until it can do so, this guarantees > >> that the PHY's probe() will have completed before EHCI's probe() > >> completes (although EHCI's probe may start running first some number of > >> times, and be retried with -EPROBE_DEFERRED for a variety of reasons). > >> > >> Now, if the PHY driver's probe() actually touches HW and sets up some > >> registers, isn't this reset call going to trash any of that register > >> setup? Or, will PHY probe() not touch registers, but only do so during > >> the standard PHY open/init "op"/API calls? > > > > Yes, PHY driver probe does not touch any registers. It just sets up the PHY > > API hooks. > > These APIs will be called from ehci-tegra.c as part of ehci tegra probe > > function, after > > getting PHY handle, which in turn happens after issuing above reset. > > > > Thanks to Stephen & Alan, for the review comments. > > OK, in that case I have no objection to this patch. > > I'd like to hold off on applying this though; I suspect I'll want to > take the Tegra USB patches through the Tegra tree rather than the USB > tree again for the 3.10 kernel cycle. I think I may have screwed the > pooch on the DT binding I set up for the USB controller clocks, and > fixing this may require some Tegra DT changes, which would be easiest > taken through the Tegra tree, and so to reduce conflicts in the USB > code, taking the rest through there migth just be easiest. > > Alan, Greg, if you're OK with this patch now, or for any revised > version, an Ack so I can take it through the Tegra tree would be great, > thanks.
Acked-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
