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Date:   Thu, 9 May 2019 02:35:56 +0000
From:   Qiang Zhao <qiang.zhao@....com>
To:     Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Leo Li <leoyang.li@....com>
CC:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Scott Wood <oss@...error.net>,
        Christophe Leroy <christophe.leroy@....fr>,
        Mark Rutland <mark.rutland@....com>,
        Rasmus Villemoes <Rasmus.Villemoes@...vas.se>
Subject: RE: [EXT] [PATCH v2 6/6] soc/fsl/qe: qe.c: fold qe_get_num_of_snums
 into qe_snums_init

On 2019/5/1 17:29, Rasmus Villemoes <rasmus.villemoes@...vas.dk> wrote:

> -----Original Message-----
> From: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
> Sent: 2019年5月1日 17:29
> To: devicetree@...r.kernel.org; Qiang Zhao <qiang.zhao@....com>; Leo Li
> <leoyang.li@....com>
> Cc: linuxppc-dev@...ts.ozlabs.org; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org; Rob Herring <robh+dt@...nel.org>; Scott Wood
> <oss@...error.net>; Christophe Leroy <christophe.leroy@....fr>; Mark
> Rutland <mark.rutland@....com>; Rasmus Villemoes
> <Rasmus.Villemoes@...vas.se>
> Subject: [PATCH v2 6/6] soc/fsl/qe: qe.c: fold qe_get_num_of_snums into
> qe_snums_init
> 
> The comment "No QE ever has fewer than 28 SNUMs" is false; e.g. the
> MPC8309 has 14. The code path returning -EINVAL is also a recipe for instant
> disaster, since the caller (qe_snums_init) uncritically assigns the return value to
> the unsigned qe_num_of_snum, and would thus proceed to attempt to copy
> 4GB from snum_init_46[] to the snum[] array.
> 
> So fold the handling of the legacy fsl,qe-num-snums into qe_snums_init, and
> make sure we do not end up using the snum_init_46 array in cases other than
> the two where we know it makes sense.
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
> ---
 
Reviewed-by: Qiang Zhao <qiang.zhao@....com>

>  drivers/soc/fsl/qe/qe.c | 46 ++++++++++++++---------------------------
>  1 file changed, 16 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/soc/fsl/qe/qe.c b/drivers/soc/fsl/qe/qe.c index
> 325d689cbf5c..276d7d78ebfc 100644
> --- a/drivers/soc/fsl/qe/qe.c
> +++ b/drivers/soc/fsl/qe/qe.c
> @@ -308,24 +308,33 @@ static void qe_snums_init(void)
>         int i;
> 
>         bitmap_zero(snum_state, QE_NUM_OF_SNUM);
> +       qe_num_of_snum = 28; /* The default number of snum for threads
> + is 28 */
>         qe = qe_get_device_node();
>         if (qe) {
>                 i = of_property_read_variable_u8_array(qe, "fsl,qe-snums",
>                                                        snums, 1,
> QE_NUM_OF_SNUM);
> -               of_node_put(qe);
>                 if (i > 0) {
> +                       of_node_put(qe);
>                         qe_num_of_snum = i;
>                         return;
>                 }
> +               /*
> +                * Fall back to legacy binding of using the value of
> +                * fsl,qe-num-snums to choose one of the static arrays
> +                * above.
> +                */
> +               of_property_read_u32(qe, "fsl,qe-num-snums",
> &qe_num_of_snum);
> +               of_node_put(qe);
>         }
> 
> -       qe_num_of_snum = qe_get_num_of_snums();
> -
> -       if (qe_num_of_snum == 76)
> +       if (qe_num_of_snum == 76) {
>                 snum_init = snum_init_76;
> -       else
> +       } else if (qe_num_of_snum == 28 || qe_num_of_snum == 46) {
>                 snum_init = snum_init_46;
> -
> +       } else {
> +               pr_err("QE: unsupported value of fsl,qe-num-snums: %u\n",
> qe_num_of_snum);
> +               return;
> +       }
>         memcpy(snums, snum_init, qe_num_of_snum);  }
> 
> @@ -641,30 +650,7 @@ EXPORT_SYMBOL(qe_get_num_of_risc);
> 
>  unsigned int qe_get_num_of_snums(void)
>  {
> -       struct device_node *qe;
> -       int size;
> -       unsigned int num_of_snums;
> -       const u32 *prop;
> -
> -       num_of_snums = 28; /* The default number of snum for threads is 28
> */
> -       qe = qe_get_device_node();
> -       if (!qe)
> -               return num_of_snums;
> -
> -       prop = of_get_property(qe, "fsl,qe-num-snums", &size);
> -       if (prop && size == sizeof(*prop)) {
> -               num_of_snums = *prop;
> -               if ((num_of_snums < 28) || (num_of_snums >
> QE_NUM_OF_SNUM)) {
> -                       /* No QE ever has fewer than 28 SNUMs */
> -                       pr_err("QE: number of snum is invalid\n");
> -                       of_node_put(qe);
> -                       return -EINVAL;
> -               }
> -       }
> -
> -       of_node_put(qe);
> -
> -       return num_of_snums;
> +       return qe_num_of_snum;
>  }
>  EXPORT_SYMBOL(qe_get_num_of_snums);
> 
> --
> 2.20.1

Best Regards
Qiang Zhao

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