Subject: Re: [PATCH v11 06/11] remoteproc: mediatek: Probe multi-core SCP

From: Mathieu Poirier <[email-masked]>
Date: Mon, 15 May 2023 11:07:52 -0600

On Mon, May 15, 2023 at 12:31:04PM +0000, TingHan Shen (沈廷翰) wrote:
> Hi Mathieu,
> 
> On Fri, 2023-05-12 at 11:56 -0600, Mathieu Poirier wrote:
> > External email : Please do not click links or open attachments until you have verified the sender or the content.
> > 
> > 
> > On Wed, May 10, 2023 at 02:37:44PM +0800, Tinghan Shen wrote:
> > > The difference of single-core SCP and multi-core SCP device tree is
> > > the presence of child device nodes described SCP cores. The SCP
> > > driver populates the platform device and checks the child nodes
> > > to identify whether it's a single-core SCP or a multi-core SCP.
> > > 
> > > Add the remoteproc instances of multi-core SCP to the SCP cluster list.
> > > When the SCP driver is removed, it cleanup resources by walking
> > > through the cluster list.
> > > 
> > > Signed-off-by: Tinghan Shen <[email-masked]>
> > > ---
> > >  drivers/remoteproc/mtk_scp.c | 135 ++++++++++++++++++++++++++++++-----
> > >  1 file changed, 117 insertions(+), 18 deletions(-)
> > > 
> > > diff --git a/drivers/remoteproc/mtk_scp.c b/drivers/remoteproc/mtk_scp.c
> > > index ff73c6dd9637..87215a0e145e 100644
> > > --- a/drivers/remoteproc/mtk_scp.c
> > > +++ b/drivers/remoteproc/mtk_scp.c
> > > @@ -864,7 +864,8 @@ static void scp_remove_rpmsg_subdev(struct mtk_scp *scp)
> > >  }
> > > 
> > >  static struct mtk_scp *scp_rproc_init(struct platform_device *pdev,
> > > -                                   struct mtk_scp_of_cluster *scp_cluster)
> > > +                                   struct mtk_scp_of_cluster *scp_cluster,
> > > +                                   const struct mtk_scp_of_data *of_data)
> > >  {
> > >       struct device *dev = &pdev->dev;
> > >       struct device_node *np = dev->of_node;
> > > @@ -887,7 +888,7 @@ static struct mtk_scp *scp_rproc_init(struct platform_device *pdev,
> > >       scp = rproc->priv;
> > >       scp->rproc = rproc;
> > >       scp->dev = dev;
> > > -     scp->data = of_device_get_match_data(dev);
> > > +     scp->data = of_data;
> > >       platform_device_add_data(pdev, &scp, sizeof(scp));
> > > 
> > >       scp->reg_base = scp_cluster->reg_base;
> > > @@ -938,10 +939,6 @@ static struct mtk_scp *scp_rproc_init(struct platform_device *pdev,
> > >               goto remove_subdev;
> > >       }
> > > 
> > > -     ret = rproc_add(rproc);
> > > -     if (ret)
> > > -             goto remove_subdev;
> > > -
> > 
> > This should have been done in the previous patch.
> 
> Ok.
> 
> > 
> > >       return scp;
> > > 
> > >  remove_subdev:
> > > @@ -956,19 +953,116 @@ static struct mtk_scp *scp_rproc_init(struct platform_device *pdev,
> > >       return ERR_PTR(ret);
> > >  }
> > > 
> > > +static void scp_rproc_free(struct mtk_scp *scp)
> > > +{
> > > +     int i;
> > > +
> > > +     scp_remove_rpmsg_subdev(scp);
> > > +     scp_ipi_unregister(scp, SCP_IPI_INIT);
> > > +     scp_unmap_memory_region(scp);
> > > +     for (i = 0; i < SCP_IPI_MAX; i++)
> > > +             mutex_destroy(&scp->ipi_desc[i].lock);
> > > +     mutex_destroy(&scp->send_lock);
> > > +}
> > > +
> > > +static int scp_is_single_core(struct platform_device *pdev)
> > > +{
> > > +     struct device *dev = &pdev->dev;
> > > +     struct device_node *np = dev_of_node(dev);
> > > +     struct device_node *child;
> > > +
> > > +     child = of_get_next_available_child(np, NULL);
> > > +     if (!child)
> > > +             return dev_err_probe(dev, -ENODEV, "No child node\n");
> > > +
> > > +     of_node_put(child);
> > > +     return of_node_name_eq(child, "cros-ec-rpmsg");
> > > +}
> > > +
> > >  static int scp_cluster_init(struct platform_device *pdev)
> > >  {
> > > -     struct mtk_scp *scp;
> > > +     struct mtk_scp *scp, *temp;
> > >       struct mtk_scp_of_cluster *scp_cluster = platform_get_drvdata(pdev);
> > >       struct list_head *cluster = &scp_cluster->mtk_scp_cluster;
> > > 
> > > -     scp = scp_rproc_init(pdev, scp_cluster);
> > > -     if (IS_ERR(scp))
> > > -             return PTR_ERR(scp);
> > > +     struct device *dev = &pdev->dev;
> > > +     struct device_node *np = dev_of_node(dev);
> > > +     struct platform_device *cpdev;
> > > +     struct device_node *child;
> > > +     const struct mtk_scp_of_data **cluster_of_data;
> > > +     int core_id = 0;
> > > +     int ret;
> > > +
> > > +     ret = scp_is_single_core(pdev);
> > > +     if (ret < 0)
> > > +             return ret;
> > > +
> > > +     if (ret) {
> > > +             dev_dbg(dev, "single-core scp\n");
> > > +
> > > +             /* When using the SCP node phandle on exported SCP APIs, the drvdata
> > > +              * is expected to be the mtk_scp object, and as a result, it is intended
> > > +              * to be overwritten for single-core SCP usage.
> > > +              */
> > 
> > Is this comment still relevant?
> 
> No, I'll remove it. 
> 
> > 
> > > +             scp = scp_rproc_init(pdev, scp_cluster, of_device_get_match_data(dev));
> > > +             if (IS_ERR(scp))
> > > +                     return PTR_ERR(scp);
> > > +
> > > +             list_add_tail(&scp->elem, cluster);
> > 
> > This is getting messy.  Please add two new functions, i.e scp_add_single_core()
> > and scp_add_multi_core().
> 
> Ok.
> 
> > 
> > > +     } else {
> > > +             dev_dbg(dev, "multi-core scp\n");
> > > +
> > > +             cluster_of_data = (const struct mtk_scp_of_data **)of_device_get_match_data(dev);
> > > +
> > > +             for_each_available_child_of_node(np, child) {
> > > +                     if (!cluster_of_data[core_id]) {
> > > +                             ret = -EINVAL;
> > > +                             dev_err(dev, "Not support core %d\n", core_id);
> > > +                             of_node_put(child);
> > > +                             goto init_fail;
> > > +                     }
> > > +
> > > +                     cpdev = of_find_device_by_node(child);
> > > +                     if (!cpdev) {
> > > +                             ret = -ENODEV;
> > > +                             dev_err(dev, "Not found platform device for core %d\n", core_id);
> > > +                             of_node_put(child);
> > > +                             goto init_fail;
> > > +                     }
> > > +
> > > +                     scp = scp_rproc_init(cpdev, scp_cluster, cluster_of_data[core_id]);
> > > +                     if (IS_ERR(scp)) {
> > > +                             dev_err(dev, "Failed to initialize core %d rproc\n", core_id);
> > > +                             put_device(&cpdev->dev);
> > > +                             of_node_put(child);
> > > +                             goto init_fail;
> > > +                     }
> > > +                     list_add_tail(&scp->elem, cluster);
> > > +                     put_device(&cpdev->dev);
> > > +
> > > +                     core_id++;
> > > +             }
> > > +     }
> > > 
> > > -     list_add_tail(&scp->elem, cluster);
> > > +     list_for_each_entry_safe_reverse(scp, temp, cluster, elem) {
> > > +             ret = rproc_add(scp->rproc);
> > 
> > Call rproc_add() in the for_each_available_child_of_node() loop above.  That way
> > it if fails you can call scp_rproc_free() right away and jump to init_fail to
> > deal with the other cores on the list.
> 
> Ok, I'll update it in next version.
> 
> > 
> > > +             if (ret)
> > > +                     goto add_fail;
> > > +     }
> > > 
> > >       return 0;
> > > +
> > > +add_fail:
> > > +     list_for_each_entry_continue(scp, cluster, elem) {
> > > +             rproc_del(scp->rproc);
> > > +     }
> > > +init_fail:
> > > +     list_for_each_entry_safe_reverse(scp, temp, cluster, elem) {
> > > +             list_del(&scp->elem);
> > > +             scp_rproc_free(scp);
> > > +     }
> > > +
> > 
> > There are a serious problems with the code in both labels above.  I will let you
> > think about that and I will stop here for this revision.
> > 
> > Mathieu
> 
> May be the problem is the possible null access of *scp?
> Or, the resources bound with cpdev should be released at here?

The first problem is related to list processing.  Function
list_for_each_entry_safe_reverse() starts at the end of the list and stops if an
error is encountered.  From there we go back the other way with
list_for_each_entry_continue() and then reverse again for
list_for_each_entry_safe_reverse().  This back and forth is error prone and very
hard to maintain.  

The second problem is with rproc_del()... Does it need to be there?

> 
> 
> > 
> > > +     return ret;
> > >  }
> > > 
> > >  static int scp_probe(struct platform_device *pdev)
> > > @@ -1005,6 +1099,10 @@ static int scp_probe(struct platform_device *pdev)
> > >       INIT_LIST_HEAD(&scp_cluster->mtk_scp_cluster);
> > >       platform_set_drvdata(pdev, scp_cluster);
> > > 
> > > +     ret = devm_of_platform_populate(dev);
> > > +     if (ret)
> > > +             return dev_err_probe(dev, ret, "Failed to populate platform devices\n");
> > > +
> > >       ret = scp_cluster_init(pdev);
> > >       if (ret)
> > >               return ret;
> > > @@ -1016,17 +1114,11 @@ static int scp_remove(struct platform_device *pdev)
> > >  {
> > >       struct mtk_scp_of_cluster *scp_cluster = platform_get_drvdata(pdev);
> > >       struct mtk_scp *scp, *temp;
> > > -     int i;
> > > 
> > >       list_for_each_entry_safe_reverse(scp, temp, &scp_cluster->mtk_scp_cluster, elem) {
> > >               list_del(&scp->elem);
> > >               rproc_del(scp->rproc);
> > > -             scp_remove_rpmsg_subdev(scp);
> > > -             scp_ipi_unregister(scp, SCP_IPI_INIT);
> > > -             scp_unmap_memory_region(scp);
> > > -             for (i = 0; i < SCP_IPI_MAX; i++)
> > > -                     mutex_destroy(&scp->ipi_desc[i].lock);
> > > -             mutex_destroy(&scp->send_lock);
> > > +             scp_rproc_free(scp);
> > >       }
> > > 
> > >       return 0;
> > > @@ -1106,12 +1198,19 @@ static const struct mtk_scp_of_data mt8195_of_data_c1 = {
> > >       .host_to_scp_int_bit = MT8195_CORE1_HOST_IPC_INT_BIT,
> > >  };
> > > 
> > > +static const struct mtk_scp_of_data *mt8195_of_data_cores[] = {
> > > +     &mt8195_of_data,
> > > +     &mt8195_of_data_c1,
> > > +     NULL
> > > +};
> > > +
> > >  static const struct of_device_id mtk_scp_of_match[] = {
> > >       { .compatible = "mediatek,mt8183-scp", .data = &mt8183_of_data },
> > >       { .compatible = "mediatek,mt8186-scp", .data = &mt8186_of_data },
> > >       { .compatible = "mediatek,mt8188-scp", .data = &mt8188_of_data },
> > >       { .compatible = "mediatek,mt8192-scp", .data = &mt8192_of_data },
> > >       { .compatible = "mediatek,mt8195-scp", .data = &mt8195_of_data },
> > > +     { .compatible = "mediatek,mt8195-scp-dual", .data = &mt8195_of_data_cores },
> > >       {},
> > >  };
> > >  MODULE_DEVICE_TABLE(of, mtk_scp_of_match);
> > > --
> > > 2.18.0
> > > 
> 
> -- 
> Best regards,
> TingHan

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