Re: [EXTERNAL] Re: [PATCH v5 1/5] soc: ti: pruss: Add pruss_get()/put() API

[Mathieu Poirier]

On Mon, 27 Mar 2023 at 23:42, Md Danish Anwar <a0501179@xxxxxx> wrote:
>
> Hi Mathieu,
>
> On 28/03/23 02:28, Mathieu Poirier wrote:
> > Hi Danish
> >
> > On Thu, Mar 23, 2023 at 11:54:47AM +0530, MD Danish Anwar wrote:
> >> From: Tero Kristo <t-kristo@xxxxxx>
> >>
> >> Add two new get and put API, pruss_get() and pruss_put() to the
> >> PRUSS platform driver to allow client drivers to request a handle
> >> to a PRUSS device. This handle will be used by client drivers to
> >> request various operations of the PRUSS platform driver through
> >> additional API that will be added in the following patches.
> >>
> >> The pruss_get() function returns the pruss handle corresponding
> >> to a PRUSS device referenced by a PRU remoteproc instance. The
> >> pruss_put() is the complimentary function to pruss_get().
> >>
> >> Co-developed-by: Suman Anna <s-anna@xxxxxx>
> >> Signed-off-by: Suman Anna <s-anna@xxxxxx>
> >> Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
> >> Co-developed-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@xxxxxxxxxx>
> >> Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@xxxxxxxxxx>
> >> Signed-off-by: Puranjay Mohan <p-mohan@xxxxxx>
> >> Signed-off-by: MD Danish Anwar <danishanwar@xxxxxx>
> >> Reviewed-by: Roger Quadros <rogerq@xxxxxxxxxx>
> >> ---
> >>  drivers/remoteproc/pru_rproc.c                |  2 +-
> >>  drivers/soc/ti/pruss.c                        | 60 ++++++++++++++++++-
> >>  .../{pruss_driver.h => pruss_internal.h}      |  7 ++-
> >>  include/linux/remoteproc/pruss.h              | 19 ++++++
> >>  4 files changed, 83 insertions(+), 5 deletions(-)
> >>  rename include/linux/{pruss_driver.h => pruss_internal.h} (90%)
> >>
> >> diff --git a/drivers/remoteproc/pru_rproc.c b/drivers/remoteproc/pru_rproc.c
> >> index b76db7fa693d..4ddd5854d56e 100644
> >> --- a/drivers/remoteproc/pru_rproc.c
> >> +++ b/drivers/remoteproc/pru_rproc.c
> >> @@ -19,7 +19,7 @@
> >>  #include <linux/of_device.h>
> >>  #include <linux/of_irq.h>
> >>  #include <linux/remoteproc/pruss.h>
> >> -#include <linux/pruss_driver.h>
> >> +#include <linux/pruss_internal.h>
> >>  #include <linux/remoteproc.h>
> >>
> >>  #include "remoteproc_internal.h"
> >> diff --git a/drivers/soc/ti/pruss.c b/drivers/soc/ti/pruss.c
> >> index 6882c86b3ce5..6c2bb02a521d 100644
> >> --- a/drivers/soc/ti/pruss.c
> >> +++ b/drivers/soc/ti/pruss.c
> >> @@ -6,6 +6,7 @@
> >>   * Author(s):
> >>   *  Suman Anna <s-anna@xxxxxx>
> >>   *  Andrew F. Davis <afd@xxxxxx>
> >> + *  Tero Kristo <t-kristo@xxxxxx>
> >>   */
> >>
> >>  #include <linux/clk-provider.h>
> >> @@ -16,8 +17,9 @@
> >>  #include <linux/of_address.h>
> >>  #include <linux/of_device.h>
> >>  #include <linux/pm_runtime.h>
> >> -#include <linux/pruss_driver.h>
> >> +#include <linux/pruss_internal.h>
> >>  #include <linux/regmap.h>
> >> +#include <linux/remoteproc.h>
> >>  #include <linux/slab.h>
> >>
> >>  /**
> >> @@ -30,6 +32,62 @@ struct pruss_private_data {
> >>      bool has_core_mux_clock;
> >>  };
> >>
> >> +/**
> >> + * pruss_get() - get the pruss for a given PRU remoteproc
> >> + * @rproc: remoteproc handle of a PRU instance
> >> + *
> >> + * Finds the parent pruss device for a PRU given the @rproc handle of the
> >> + * PRU remote processor. This function increments the pruss device's refcount,
> >> + * so always use pruss_put() to decrement it back once pruss isn't needed
> >> + * anymore.
> >> + *
> >> + * Return: pruss handle on success, and an ERR_PTR on failure using one
> >> + * of the following error values
> >> + *    -EINVAL if invalid parameter
> >> + *    -ENODEV if PRU device or PRUSS device is not found
> >> + */
> >> +struct pruss *pruss_get(struct rproc *rproc)
> >> +{
> >> +    struct pruss *pruss;
> >> +    struct device *dev;
> >> +    struct platform_device *ppdev;
> >> +
> >> +    if (IS_ERR_OR_NULL(rproc))
> >> +            return ERR_PTR(-EINVAL);
> >> +
> >
> > There is no guarantee that @rproc is valid without calling rproc_get_by_handle()
> > or pru_rproc_get().
> >
>
> Here in this API, we are checking if rproc is NULL or not. Also we are checking
> is_pru_rproc() to make sure this rproc is pru-rproc only and not some other rproc.
>
> This API will be called from driver (icssg_prueth.c) which I'll post once this
> series is merged.
>
> In the driver we are doing,
>
>         prueth->pru[slice] = pru_rproc_get(np, pru, &pruss_id);
>
>         pruss = pruss_get(prueth->pru[slice]);
>
> So, before calling pruss_get() we are in fact calling pru_rproc_get() to make
> sure it's a valid rproc.
>

You are doing the right thing but because pruss_get() is exported
globally, other people eventually using the interface may not be so
rigorous.  Add a comment to the pruss_get() function documentation
clearly mentioning it is expected the caller will have done a
pru_rproc_get() on @rproc.

> I think in this API, these two checks (NULL check and is_pru_rproc) should be
> OK as the driver is already calling pru_rproc_get() before this API.
>
> The only way to get a "pru-rproc" is by calling pru_rproc_get(), now the check
> is_pru_rproc() will only be true if it is a "pru-rproc" implying
> pru_rproc_get() was called before calling this API.
>
> Please let me know if this is OK or if any change is required.
>
> >> +    dev = &rproc->dev;
> >> +
> >> +    /* make sure it is PRU rproc */
> >> +    if (!dev->parent || !is_pru_rproc(dev->parent))
> >> +            return ERR_PTR(-ENODEV);
> >> +
> >> +    ppdev = to_platform_device(dev->parent->parent);
> >> +    pruss = platform_get_drvdata(ppdev);
> >> +    if (!pruss)
> >> +            return ERR_PTR(-ENODEV);
> >> +
> >> +    get_device(pruss->dev);
> >> +
> >> +    return pruss;
> >> +}
> >> +EXPORT_SYMBOL_GPL(pruss_get);
> >> +
> >> +/**
> >> + * pruss_put() - decrement pruss device's usecount
> >> + * @pruss: pruss handle
> >> + *
> >> + * Complimentary function for pruss_get(). Needs to be called
> >> + * after the PRUSS is used, and only if the pruss_get() succeeds.
> >> + */
> >> +void pruss_put(struct pruss *pruss)
> >> +{
> >> +    if (IS_ERR_OR_NULL(pruss))
> >> +            return;
> >> +
> >> +    put_device(pruss->dev);
> >> +}
> >> +EXPORT_SYMBOL_GPL(pruss_put);
> >> +
> >>  static void pruss_of_free_clk_provider(void *data)
> >>  {
> >>      struct device_node *clk_mux_np = data;
> >> diff --git a/include/linux/pruss_driver.h b/include/linux/pruss_internal.h
> >> similarity index 90%
> >> rename from include/linux/pruss_driver.h
> >> rename to include/linux/pruss_internal.h
> >> index ecfded30ed05..8f91cb164054 100644
> >> --- a/include/linux/pruss_driver.h
> >> +++ b/include/linux/pruss_internal.h
> >> @@ -6,9 +6,10 @@
> >>   *  Suman Anna <s-anna@xxxxxx>
> >>   */
> >>
> >> -#ifndef _PRUSS_DRIVER_H_
> >> -#define _PRUSS_DRIVER_H_
> >> +#ifndef _PRUSS_INTERNAL_H_
> >> +#define _PRUSS_INTERNAL_H_
> >>
> >> +#include <linux/remoteproc/pruss.h>
> >>  #include <linux/types.h>
> >>
> >>  /*
> >> @@ -51,4 +52,4 @@ struct pruss {
> >>      struct clk *iep_clk_mux;
> >>  };
> >>
> >> -#endif      /* _PRUSS_DRIVER_H_ */
> >> +#endif      /* _PRUSS_INTERNAL_H_ */
> >> diff --git a/include/linux/remoteproc/pruss.h b/include/linux/remoteproc/pruss.h
> >> index 039b50d58df2..93a98cac7829 100644
> >> --- a/include/linux/remoteproc/pruss.h
> >> +++ b/include/linux/remoteproc/pruss.h
> >> @@ -4,12 +4,14 @@
> >>   *
> >>   * Copyright (C) 2015-2022 Texas Instruments Incorporated - http://www.ti.com
> >>   *  Suman Anna <s-anna@xxxxxx>
> >> + *  Tero Kristo <t-kristo@xxxxxx>
> >>   */
> >>
> >>  #ifndef __LINUX_PRUSS_H
> >>  #define __LINUX_PRUSS_H
> >>
> >>  #include <linux/device.h>
> >> +#include <linux/err.h>
> >>  #include <linux/types.h>
> >>
> >>  #define PRU_RPROC_DRVNAME "pru-rproc"
> >> @@ -44,6 +46,23 @@ enum pru_ctable_idx {
> >>
> >>  struct device_node;
> >>  struct rproc;
> >> +struct pruss;
> >> +
> >> +#if IS_ENABLED(CONFIG_TI_PRUSS)
> >> +
> >> +struct pruss *pruss_get(struct rproc *rproc);
> >> +void pruss_put(struct pruss *pruss);
> >> +
> >> +#else
> >> +
> >> +static inline struct pruss *pruss_get(struct rproc *rproc)
> >> +{
> >> +    return ERR_PTR(-EOPNOTSUPP);
> >> +}
> >> +
> >> +static inline void pruss_put(struct pruss *pruss) { }
> >> +
> >> +#endif /* CONFIG_TI_PRUSS */
> >>
> >>  #if IS_ENABLED(CONFIG_PRU_REMOTEPROC)
> >>
> >> --
> >> 2.25.1
> >>
>
> --
> Thanks and Regards,
> Danish.