Re: [PATCH] coresight: etm4x: lazily allocate memory for save_state

From: Mathieu Poirier <mathieu.poirier@linaro.org>
To: Andrew Murray <andrew.murray@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Coresight ML <coresight@lists.linaro.org>,
	Leo Yan <leo.yan@linaro.org>, Sudeep Holla <sudeep.holla@arm.com>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Mike Leach <mike.leach@linaro.org>
Subject: Re: [PATCH] coresight: etm4x: lazily allocate memory for save_state
Date: Mon, 22 Jul 2019 14:32:07 -0600	[thread overview]
Message-ID: <CANLsYkyE2erOeSM69XTVL-oizFj6WhXLcSKGT2qnFr0ArNskzA@mail.gmail.com> (raw)
In-Reply-To: <20190712150056.15775-1-andrew.murray@arm.com>

Hi Andrew,

Sorry for the late reply - you patch got lost under the pile.

On Fri, 12 Jul 2019 at 09:01, Andrew Murray <andrew.murray@arm.com> wrote:
>
> I had intended to lazily allocate memory for the save_state structure when
> it is first used. Following is a patch that I will squash into "[PATCH v3 5/6]
> coresight: etm4x: save/restore state across CPU low power states" on my
> next respin. I thought I'd share it here to get some feedback along with
> the rest of v3.
>
> Thanks,
>
> Andrew Murray
>
> ---
>  drivers/hwtracing/coresight/coresight-etm4x.c | 14 +++++++++++---
>  drivers/hwtracing/coresight/coresight-etm4x.h |  2 +-
>  2 files changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index b0bd8158bf13..cd02372194bc 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> @@ -1112,6 +1112,13 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
>         struct etmv4_save_state *state;
>         struct device *etm_dev = &drvdata->csdev->dev;
>
> +       if (!drvdata->save_state) {
> +               drvdata->save_state = devm_kmalloc(etm_dev,
> +                               sizeof(struct etmv4_save_state), GFP_KERNEL);

GFP_KERNEL may sleep and will not work in the context where
etm4_cpu_save() is called.

Thanks,
Mathieu

> +               if (!drvdata->save_state)
> +                       return -ENOMEM;
> +       }
> +
>         /*
>          * As recommended by 3.4.1 ("The procedure when powering down the PE")
>          * of ARM IHI 0064D
> @@ -1134,7 +1141,7 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
>                 goto out;
>         }
>
> -       state = &drvdata->save_state;
> +       state = drvdata->save_state;
>
>         state->trcprgctlr = readl(drvdata->base + TRCPRGCTLR);
>         state->trcprocselr = readl(drvdata->base + TRCPROCSELR);
> @@ -1234,9 +1241,10 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
>  static void etm4_cpu_restore(struct etmv4_drvdata *drvdata)
>  {
>         int i;
> -       struct etmv4_save_state *state;
> +       struct etmv4_save_state *state = drvdata->save_state;
>
> -       state = &drvdata->save_state;
> +       if (WARN_ON_ONCE(!state))
> +               return;
>
>         CS_UNLOCK(drvdata->base);
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
> index c31634c64f87..a70cafbbb8cf 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
> @@ -441,7 +441,7 @@ struct etmv4_drvdata {
>         bool                            atbtrig;
>         bool                            lpoverride;
>         struct etmv4_config             config;
> -       struct etmv4_save_state         save_state;
> +       struct etmv4_save_state         *save_state;
>         bool                            state_needs_restore;
>  };
>
> --
> 2.21.0
>

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