Re: [PATCH 2/2] soc: fsl: dpio: use a cpumask to identify which cpus are unused

[Li Yang]

On Mon, Nov 5, 2018 at 3:31 AM Ioana Ciornei <ioana.ciornei@xxxxxxx> wrote:
>
> The current implementation of the dpio driver uses a static next_cpu
> variable to keep track of the index of the next cpu available. This
> approach does not handle well unbinding and binding dpio devices in a
> random order. For example, unbinding a dpio and then binding it again
> with the driver, will generate the below error:
>
> $ echo dpio.5 > /sys/bus/fsl-mc/drivers/fsl_mc_dpio/unbind
> $ echo dpio.5 > /sys/bus/fsl-mc/drivers/fsl_mc_dpio/bind
> [  103.946380] fsl_mc_dpio dpio.5: probe failed. Number of DPIOs exceeds
> NR_CPUS.
> [  103.955157] fsl_mc_dpio dpio.5: fsl_mc_driver_probe failed: -34
> -bash: echo: write error: No such device
>
> Fix this error by keeping a global cpumask of unused cpus that will be
> updated at every dpaa2_dpio_[probe,remove].
>
> Signed-off-by: Ioana Ciornei <ioana.ciornei@xxxxxxx>
> ---
>  drivers/soc/fsl/dpio/dpio-driver.c  | 25 ++++++++++++++++---------
>  drivers/soc/fsl/dpio/dpio-service.c |  6 ++++++
>  include/soc/fsl/dpaa2-io.h          |  2 ++
>  3 files changed, 24 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/soc/fsl/dpio/dpio-driver.c b/drivers/soc/fsl/dpio/dpio-driver.c
> index e58fcc9..832175c 100644
> --- a/drivers/soc/fsl/dpio/dpio-driver.c
> +++ b/drivers/soc/fsl/dpio/dpio-driver.c
> @@ -30,6 +30,8 @@ struct dpio_priv {
>         struct dpaa2_io *io;
>  };
>
> +static cpumask_var_t cpus_unused_mask;
> +
>  static irqreturn_t dpio_irq_handler(int irq_num, void *arg)
>  {
>         struct device *dev = (struct device *)arg;
> @@ -86,7 +88,7 @@ static int dpaa2_dpio_probe(struct fsl_mc_device *dpio_dev)
>         struct dpio_priv *priv;
>         int err = -ENOMEM;
>         struct device *dev = &dpio_dev->dev;
> -       static int next_cpu = -1;
> +       int possible_next_cpu;
>
>         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>         if (!priv)
> @@ -128,17 +130,14 @@ static int dpaa2_dpio_probe(struct fsl_mc_device *dpio_dev)
>         desc.dpio_id = dpio_dev->obj_desc.id;
>
>         /* get the cpu to use for the affinity hint */
> -       if (next_cpu == -1)
> -               next_cpu = cpumask_first(cpu_online_mask);
> -       else
> -               next_cpu = cpumask_next(next_cpu, cpu_online_mask);
> -
> -       if (!cpu_possible(next_cpu)) {
> +       possible_next_cpu = cpumask_first(cpus_unused_mask);
> +       if (possible_next_cpu >= nr_cpu_ids) {
>                 dev_err(dev, "probe failed. Number of DPIOs exceeds NR_CPUS.\n");
>                 err = -ERANGE;
>                 goto err_allocate_irqs;
>         }
> -       desc.cpu = next_cpu;
> +       desc.cpu = possible_next_cpu;
> +       cpumask_clear_cpu(possible_next_cpu, cpus_unused_mask);
>
>         /*
>          * Set the CENA regs to be the cache inhibited area of the portal to
> @@ -211,7 +210,7 @@ static int dpaa2_dpio_remove(struct fsl_mc_device *dpio_dev)
>  {
>         struct device *dev;
>         struct dpio_priv *priv;
> -       int err;
> +       int err = 0, cpu;
>
>         dev = &dpio_dev->dev;
>         priv = dev_get_drvdata(dev);
> @@ -220,6 +219,9 @@ static int dpaa2_dpio_remove(struct fsl_mc_device *dpio_dev)
>
>         dpio_teardown_irqs(dpio_dev);
>
> +       cpu = dpaa2_io_get_cpu(priv->io);
> +       cpumask_set_cpu(cpu, cpus_unused_mask);
> +
>         err = fsl_mc_portal_allocate(dpio_dev, 0, &dpio_dev->mc_io);
>         if (err) {
>                 dev_err(dev, "MC portal allocation failed\n");
> @@ -267,11 +269,16 @@ static int dpaa2_dpio_remove(struct fsl_mc_device *dpio_dev)
>
>  static int dpio_driver_init(void)
>  {
> +       if (!zalloc_cpumask_var(&cpus_unused_mask, GFP_KERNEL))
> +               return -ENOMEM;
> +       cpumask_copy(cpus_unused_mask, cpu_online_mask);
> +
>         return fsl_mc_driver_register(&dpaa2_dpio_driver);
>  }
>
>  static void dpio_driver_exit(void)
>  {
> +       free_cpumask_var(cpus_unused_mask);
>         fsl_mc_driver_unregister(&dpaa2_dpio_driver);
>  }
>  module_init(dpio_driver_init);
> diff --git a/drivers/soc/fsl/dpio/dpio-service.c b/drivers/soc/fsl/dpio/dpio-service.c
> index 21c3e32..3198265 100644
> --- a/drivers/soc/fsl/dpio/dpio-service.c
> +++ b/drivers/soc/fsl/dpio/dpio-service.c
> @@ -214,6 +214,12 @@ irqreturn_t dpaa2_io_irq(struct dpaa2_io *obj)
>         return IRQ_HANDLED;
>  }
>
> +int dpaa2_io_get_cpu(struct dpaa2_io *d)
> +{
> +       return d->dpio_desc.cpu;
> +}
> +EXPORT_SYMBOL(dpaa2_io_get_cpu);

Although this function is very simple function and probably
self-explanatory, it is required that exported APIs have a kernel-doc
comment just like other functions in the file.

> +
>  /**
>   * dpaa2_io_service_register() - Prepare for servicing of FQDAN or CDAN
>   *                               notifications on the given DPIO service.
> diff --git a/include/soc/fsl/dpaa2-io.h b/include/soc/fsl/dpaa2-io.h
> index ab51e40..1c1764f 100644
> --- a/include/soc/fsl/dpaa2-io.h
> +++ b/include/soc/fsl/dpaa2-io.h
> @@ -90,6 +90,8 @@ struct dpaa2_io_notification_ctx {
>         void *dpio_private;
>  };
>
> +int dpaa2_io_get_cpu(struct dpaa2_io *d);
> +
>  int dpaa2_io_service_register(struct dpaa2_io *service,
>                               struct dpaa2_io_notification_ctx *ctx);
>  void dpaa2_io_service_deregister(struct dpaa2_io *service,
> --
> 1.9.1
>