linux-kernel - Re: [PATCH 3/4] 44x/fsp2: tvsense workaround for dd1

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Date:   Mon, 27 Nov 2017 16:50:34 +1100
From:   Alistair Popple <alistair@...ple.id.au>
To:     Ivan Mikhaylov <ivan@...ibm.com>
Cc:     Matt Porter <mporter@...nel.crashing.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Joel Stanley <joel@....id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 3/4] 44x/fsp2: tvsense workaround for dd1

Again, I'm not familiar with this specific hardware so can only provide general
comments.

On Thursday, 2 November 2017 4:07:05 PM AEDT Ivan Mikhaylov wrote:
> * tvsense(temperature and voltage sensors) may provide
>   erratic sense values which may result in parity errors
>   on CMU.

It would be good if you could provide a more detailed description of the problem
(like in the comment below) and what this patch does to address it.

Feel free to add my reviewed by as well.

- Alistair

> Signed-off-by: Ivan Mikhaylov <ivan@...ibm.com>
> ---
>  arch/powerpc/platforms/44x/fsp2.c |   17 +++++++++++++++++
>  1 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/44x/fsp2.c b/arch/powerpc/platforms/44x/fsp2.c
> index 9585725..4e12490 100644
> --- a/arch/powerpc/platforms/44x/fsp2.c
> +++ b/arch/powerpc/platforms/44x/fsp2.c
> @@ -59,6 +59,23 @@ static int __init fsp2_probe(void)
>  	mtdcr(DCRN_PLB6_HD, 0xffff0000);
>  	mtdcr(DCRN_PLB6_SHD, 0xffff0000);
>  
> +	/* TVSENSE reset is blocked (clock gated) by the POR default of the TVS
> +	 * sleep config bit. As a consequence, TVSENSE will provide erratic
> +	 * sensor values, which may result in spurious (parity) errors
> +	 * recorded in the CMU FIR and leading to erroneous interrupt requests
> +	 * once the CMU interrupt is unmasked.
> +	 */
> +
> +	/* 1. set TVS1[UNDOZE] */
> +	val = mfcmu(CMUN_TVS1);
> +	val |= 0x4;
> +	mtcmu(CMUN_TVS1, val);
> +
> +	/* 2. clear FIR[TVS] and FIR[TVSPAR] */
> +	val = mfcmu(CMUN_FIR0);
> +	val |= 0x30000000;
> +	mtcmu(CMUN_FIR0, val);
> +
>  	/* L2 machine checks */
>  	mtl2(L2PLBMCKEN0, 0xffffffff);
>  	mtl2(L2PLBMCKEN1, 0x0000ffff);
>