linux-kernel - Re: [RFC 11/12] arm_mpam: Fix Downstream priority mask

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Message-ID: <20230901143233.0000480e@Huawei.com>
Date:   Fri, 1 Sep 2023 14:32:33 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Amit Singh Tomar <amitsinght@...vell.com>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <fenghua.yu@...el.com>,
        <reinette.chatre@...el.com>, <james.morse@....com>,
        <gcherian@...vell.com>, <robh@...nel.org>, <peternewman@...gle.com>
Subject: Re: [RFC 11/12] arm_mpam: Fix Downstream priority mask

On Tue, 15 Aug 2023 20:57:11 +0530
Amit Singh Tomar <amitsinght@...vell.com> wrote:

> MPAMF_PRI_IDR_NS[DSPRI_WD] determines the number of implemented bits in
> the downstream priority field (MPAMCFG_PRI_NS). For instance, if the value
> of DSPRI_WD is 4, then the maximum value for dspri is 0xf, and mask should
> be GENMASK(3,0).
> 
> But with current implementation, it turned out to be GENMASK(4,0) .i.e.
> 0x1f instead of 0xf.
> 
> u16 dspri = GENMASK(rprops->dspri_wd, 0);
> 
> Let's fix it, by subtracting 1 from DSPRI_WD value.
> 
> Signed-off-by: Amit Singh Tomar <amitsinght@...vell.com>

> ---
>  drivers/platform/mpam/mpam_devices.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/mpam/mpam_devices.c b/drivers/platform/mpam/mpam_devices.c
> index c0c83c04c77c..59022e42920c 100644
> --- a/drivers/platform/mpam/mpam_devices.c
> +++ b/drivers/platform/mpam/mpam_devices.c
> @@ -1099,7 +1099,7 @@ static void mpam_reprogram_ris_partid(struct mpam_msc_ris *ris, u16 partid,
>  	struct mpam_msc *msc = ris->msc;
>  	u16 bwa_fract = MPAMCFG_MBW_MAX_MAX;
>  	struct mpam_props *rprops = &ris->props;
> -	u16 dspri = GENMASK(rprops->dspri_wd, 0);
> +	u16 dspri = GENMASK((rprops->dspri_wd-1), 0);

Spaces around the -

>  	u16 intpri = GENMASK(rprops->intpri_wd, 0);

Please fix intpri as well. Argument is the same.

I'm assuming / hoping James will squash this into relevant patch in his tree.

>  
>  	lockdep_assert_held(&msc->lock);