linux-kernel - Re: [PATCH] Coresight: ETMv4: Prevent TRCRSCTLR0&1 from being accessed

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Date:	Thu, 27 Aug 2015 09:05:33 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	Chunyan Zhang <zhang.chunyan@...aro.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Mark Brown <broonie@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Coresight: ETMv4: Prevent TRCRSCTLR0&1 from being accessed

On 26 August 2015 at 22:06, Chunyan Zhang <zhang.chunyan@...aro.org> wrote:
> 1. TRCRSCTLRn - Resource Selection Control Registers n=0~1 are reserved,
>    we shouldn't access them.
> 2. The max number of 'n' here is defined in TRCIDR4.NUMRSPAIR whoes value
>    indicates the number of resource selection *pairs*, and 0 indicates
>    one resource selection pair, 1 indicates two pairs, and so on ...
>
> So, the total number of resource selection control registers which we can
> access is (TRCIDR4.NUMRSPAIR * 2)
>
> Signed-off-by: Chunyan Zhang <zhang.chunyan@...aro.org>
> ---
>  drivers/hwtracing/coresight/coresight-etm4x.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index 1312e99..9425249 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> @@ -136,7 +136,9 @@ static void etm4_enable_hw(void *info)
>                 writel_relaxed(drvdata->cntr_val[i],
>                                drvdata->base + TRCCNTVRn(i));
>         }
> -       for (i = 0; i < drvdata->nr_resource; i++)
> +
> +       /* Resource selector pair 0 is always implemented and reserved */
> +       for (i = 2; i < (drvdata->nr_resource + 1) * 2; i++)

Instead of repeating "->nr_resource + 1) * 2" every time, please add
"->nr_resource += 1" in etm4_init_arch_data() along with a comment
that explains why.

>                 writel_relaxed(drvdata->res_ctrl[i],
>                                drvdata->base + TRCRSCTLRn(i));
>
> @@ -489,8 +491,9 @@ static ssize_t reset_store(struct device *dev,
>                 drvdata->cntr_val[i] = 0x0;
>         }
>
> -       drvdata->res_idx = 0x0;
> -       for (i = 0; i < drvdata->nr_resource; i++)
> +       /* Resource selector pair 0 is always implemented and reserved */
> +       drvdata->res_idx = 0x2;
> +       for (i = 2; i < (drvdata->nr_resource + 1) * 2; i++)
>                 drvdata->res_ctrl[i] = 0x0;
>
>         for (i = 0; i < drvdata->nr_ss_cmp; i++) {
> @@ -1729,7 +1732,7 @@ static ssize_t res_idx_store(struct device *dev,
>         if (kstrtoul(buf, 16, &val))
>                 return -EINVAL;
>         /* Resource selector pair 0 is always implemented and reserved */
> -       if ((val == 0) || (val >= drvdata->nr_resource))
> +       if (val < 2 || val > (drvdata->nr_resource + 1) * 2)
>                 return -EINVAL;
>
>         /*
> @@ -2498,7 +2501,9 @@ static void etm4_init_default_data(struct etmv4_drvdata *drvdata)
>                 drvdata->cntr_val[i] = 0x0;
>         }
>
> -       for (i = 2; i < drvdata->nr_resource * 2; i++)
> +       /* Resource selector pair 0 is always implemented and reserved */
> +       drvdata->res_idx = 0x2;
> +       for (i = 2; i < (drvdata->nr_resource + 1) * 2; i++)
>                 drvdata->res_ctrl[i] = 0x0;
>
>         for (i = 0; i < drvdata->nr_ss_cmp; i++) {
> --
> 1.9.1
>
--
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