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

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Message-ID: <2feb313b-ef9f-be2f-68a5-b8cc46ad75c3@nvidia.com>
Date:   Fri, 2 Mar 2018 08:56:46 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Marcel Ziswiler <marcel@...wiler.com>,
        <linux-tegra@...r.kernel.org>
CC:     Dmitry Osipenko <digetx@...il.com>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Stephen Boyd <sboyd@...nel.org>,
        <linux-kernel@...r.kernel.org>,
        "Prashant Gaikwad" <pgaikwad@...dia.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Michael Turquette <mturquette@...libre.com>,
        <linux-clk@...r.kernel.org>
Subject: Re: [PATCH] clk: tegra: fix pllu rate configuration


On 22/02/18 23:04, 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@...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(+)
> 
> diff --git a/drivers/clk/tegra/clk-pll.c b/drivers/clk/tegra/clk-pll.c
> index 7c369e21c91c..830d1c87fa7c 100644
> --- a/drivers/clk/tegra/clk-pll.c
> +++ b/drivers/clk/tegra/clk-pll.c
> @@ -1151,6 +1151,8 @@ static const struct clk_ops tegra_clk_pllu_ops = {
>  	.enable = clk_pllu_enable,
>  	.disable = clk_pll_disable,
>  	.recalc_rate = clk_pll_recalc_rate,
> +	.round_rate = clk_pll_round_rate,
> +	.set_rate = clk_pll_set_rate,
>  };
>  
>  static int _pll_fixed_mdiv(struct tegra_clk_pll_params *pll_params,

Thanks for the fix. I have tested this on Tegra30 cardhu and this
resolves a problem booting this board with the upstream uboot bootloader.

We just need to align with Peter on the best way to fix.

Cheers,
Jon

-- 
nvpublic