linux-kernel - Re: [PATCH] clk: tegra: fix pllu rate configuration

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Date:   Thu, 8 Mar 2018 15:57:43 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Marcel Ziswiler <marcel@...wiler.com>
Cc:     linux-tegra@...r.kernel.org, Dmitry Osipenko <digetx@...il.com>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-kernel@...r.kernel.org,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Michael Turquette <mturquette@...libre.com>,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH] clk: tegra: fix pllu rate configuration

On Fri, Feb 23, 2018 at 12:04:51AM +0100, 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@...lis-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.
> 
> Signed-off-by: Marcel Ziswiler <marcel.ziswiler@...adex.com>
> 
> ---
> 
>  drivers/clk/tegra/clk-pll.c | 2 ++
>  1 file changed, 2 insertions(+)

I'm aware of the discussion about how best to implement this, but this
seems like a reasonable fix until we have something better.

Peter, Jon: if you want to fix this more properly, please take point on
this.

Applied this to for-4.17/clk, thanks.

Thierry

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