From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH] clk: tegra: fix pllu rate configuration Date: Fri, 2 Mar 2018 09:02:07 +0000 Message-ID: <7914774e-e88f-7914-2434-790a67f3aa4e@nvidia.com> References: <20180222230451.15515-1-marcel@ziswiler.com> <31f039e8-9afc-22d1-d478-a7f41db0dace@gmail.com> <1519686262.6374.3.camel@toradex.com> <20180228093620.GC6190@tbergstrom-lnx.Nvidia.com> <20180228141448.GD6190@tbergstrom-lnx.Nvidia.com> <7d8d77ca-e18d-6e37-1aca-6dd7c6e1964d@gmail.com> <20180301074129.GG6190@tbergstrom-lnx.Nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180301074129.GG6190@tbergstrom-lnx.Nvidia.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Peter De Schrijver , Dmitry Osipenko Cc: Marcel Ziswiler , "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "mturquette@baylibre.com" , "pgaikwad@nvidia.com" , "sboyd@kernel.org" , "thierry.reding@gmail.com" , "linux-clk@vger.kernel.org" List-Id: linux-tegra@vger.kernel.org On 01/03/18 07:41, Peter De Schrijver wrote: > On Wed, Feb 28, 2018 at 08:20:47PM +0300, Dmitry Osipenko wrote: >> On 28.02.2018 17:14, Peter De Schrijver wrote: >>> On Wed, Feb 28, 2018 at 03:00:23PM +0300, Dmitry Osipenko wrote: >>>> 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. >>>> >>> >>> AFAIK we only use one rate ever? >> >> IIUC, PLL_U has 3 outputs and output dividers are fixed in HW. So yes, we are >> setting PLL_U to one rate - 480MHz to get out1-480MHz, out2-60MHz and out3-12MHz. >> > > Indeed. And given that it's hw controlled anyway, I don't see why we can't make > it a fixed clock and handle the init at kernel boot depending on what the > bootloader has done. Peter, are you suggesting we implement the equivalent to tegra210_init_pllu()? This does look a bit more involved that what this change is doing. Is there a simple way to do what you are suggesting? Cheers Jon -- nvpublic