On 28.02.2018 12:36, Peter De Schrijver wrote: > On Tue, Feb 27, 2018 at 02:59:11PM +0300, Dmitry Osipenko wrote: >> On 27.02.2018 02:04, Marcel Ziswiler wrote: >>> On Mon, 2018-02-26 at 15:42 +0300, Dmitry Osipenko wrote: >>>> On 23.02.2018 02:04, Marcel Ziswiler wrote: >>>>> Turns out latest upstream U-Boot does not configure/enable pllu >>>>> which >>>>> leaves it at some default rate of 500 kHz: >>>>> >>>>> root@apalis-t30:~# cat /sys/kernel/debug/clk/clk_summary | grep >>>>> pll_u >>>>> pll_u 3 3 0 500000 >>>>> 0 >>>>> >>>>> Of course this won't quite work leading to the following messages: >>>>> >>>>> [ 6.559593] usb 2-1: new full-speed USB device number 2 using >>>>> tegra- >>>>> ehci >>>>> [ 11.759173] usb 2-1: device descriptor read/64, error -110 >>>>> [ 27.119453] usb 2-1: device descriptor read/64, error -110 >>>>> [ 27.389217] usb 2-1: new full-speed USB device number 3 using >>>>> tegra- >>>>> ehci >>>>> [ 32.559454] usb 2-1: device descriptor read/64, error -110 >>>>> [ 47.929777] usb 2-1: device descriptor read/64, error -110 >>>>> [ 48.049658] usb usb2-port1: attempt power cycle >>>>> [ 48.759475] usb 2-1: new full-speed USB device number 4 using >>>>> tegra- >>>>> ehci >>>>> [ 59.349457] usb 2-1: device not accepting address 4, error -110 >>>>> [ 59.509449] usb 2-1: new full-speed USB device number 5 using >>>>> tegra- >>>>> ehci >>>>> [ 70.069457] usb 2-1: device not accepting address 5, error -110 >>>>> [ 70.079721] usb usb2-port1: unable to enumerate USB device >>>>> >>>>> Fix this by actually allowing the rate also being set from within >>>>> the Linux kernel. > > I think the best solution to this problem would be to make pll_u a fixed > clock and enable it and program the rate if it's not enabled at boot. Oh, right. PLL_U rate is actually configurable, somehow I missed it in TRM yesterday.. So set/round_rate() for PLL_U are actually needed and the patch is correct. Seems only T20 misses PLL_U in the init table, probably worth to add it there. > This is how it's done for Tegra210. The reason is that the USB IP blocks > can control the pll_u state in hw. This means that if sw would disable > and then re-enable the pll_u clock, but there is no USB activity, pll_u > will still be disable and therefor not lock, causing an error. Today > this is worked around by not polling the lock bit for pll_u, but a better > solution would be to just remove all sw controls for pll_u. SW controls could be removed, but I don't think it is really necessary as in our case SW is the PHY driver and we know what it does. Alternatively we can enable PLL_U in the init table to keep it "always" enabled. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
