On 12/03/18 15:24, Nipun Gupta wrote:
The change introduces 'dma_configure' & 'dma_deconfigure'as
bus callback functions so each bus can choose to implement
its own dma configuration function.
This eases the addition of new busses w.r.t. adding the dma
configuration functionality.


It's probably worth clarifying - either in the commit message, the kerneldoc, or both - that the bus-specific aspect is that of mapping between a given device on the bus and the relevant firmware description of its DMA configuration.

The change also updates the PCI, Platform and ACPI bus to use
new introduced callbacks.

Signed-off-by: Nipun Gupta <nipun.gu...@nxp.com>
---
  - This patch is based on the comments on:
    https://patchwork.kernel.org/patch/10259087/
  - I have validated for PCI and platform, but not for AMBA as I
    do not have infrastructure to validate it.
    Can anyone please validate them on AMBA?

  drivers/amba/bus.c          | 38 ++++++++++++++++++++++++-----
  drivers/base/dd.c           | 14 +++++++----
  drivers/base/dma-mapping.c  | 41 -------------------------------
  drivers/base/platform.c     | 36 ++++++++++++++++++++++-----
  drivers/pci/pci-driver.c    | 59 ++++++++++++++++++++++++++++++++++++---------
  include/linux/device.h      |  6 +++++
  include/linux/dma-mapping.h | 12 ---------
  7 files changed, 124 insertions(+), 82 deletions(-)

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index 594c228..58241d2 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -20,6 +20,8 @@
  #include <linux/sizes.h>
  #include <linux/limits.h>
  #include <linux/clk/clk-conf.h>
+#include <linux/acpi.h>
+#include <linux/of_device.h>
#include <asm/irq.h> @@ -171,6 +173,28 @@ static int amba_pm_runtime_resume(struct device *dev)
  }
  #endif /* CONFIG_PM */
+int amba_dma_configure(struct device *dev)
+{
+       enum dev_dma_attr attr;
+       int ret = 0;
+
+       if (dev->of_node) {
+               ret = of_dma_configure(dev, dev->of_node);
+       } else if (has_acpi_companion(dev)) {
+               attr = acpi_get_dma_attr(to_acpi_device_node(dev->fwnode));
+               if (attr != DEV_DMA_NOT_SUPPORTED)
+                       ret = acpi_dma_configure(dev, attr);
+       }
+
+       return ret;
+}

I would be inclined to have amba_bustype just reference platform_dma_configure() directly rather than duplicate it like this, since there's no sensible reason for them to ever differ.

+
+void amba_dma_deconfigure(struct device *dev)
+{
+       of_dma_deconfigure(dev);
+       acpi_dma_deconfigure(dev);
+}
+
  static const struct dev_pm_ops amba_pm = {
        .suspend        = pm_generic_suspend,
        .resume         = pm_generic_resume,
@@ -190,12 +214,14 @@ static int amba_pm_runtime_resume(struct device *dev)
   * so we call the bus "amba".
   */
  struct bus_type amba_bustype = {
-       .name           = "amba",
-       .dev_groups     = amba_dev_groups,
-       .match          = amba_match,
-       .uevent         = amba_uevent,
-       .pm             = &amba_pm,
-       .force_dma      = true,
+       .name                   = "amba",
+       .dev_groups             = amba_dev_groups,
+       .match                  = amba_match,
+       .uevent                 = amba_uevent,
+       .pm                     = &amba_pm,
+       .dma_configure          = amba_dma_configure,
+       .dma_deconfigure        = amba_dma_deconfigure,
+       .force_dma              = true,

This patch should also be removing force_dma because it no longer makes sense. If DMA configuration is now done by a bus-level callback, then a bus which wants its children to get DMA configuration needs to implement that callback; there's nowhere to force a "default" global behaviour any more.

  };
static int __init amba_init(void)
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index de6fd09..f124f3f 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -421,9 +421,11 @@ static int really_probe(struct device *dev, struct 
device_driver *drv)
        if (ret)
                goto pinctrl_bind_failed;
- ret = dma_configure(dev);
-       if (ret)
-               goto dma_failed;
+       if (dev->bus->dma_configure) {
+               ret = dev->bus->dma_configure(dev);
+               if (ret)
+                       goto dma_failed;
+       }
if (driver_sysfs_add(dev)) {
                printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
@@ -486,7 +488,8 @@ static int really_probe(struct device *dev, struct 
device_driver *drv)
        goto done;
probe_failed:
-       dma_deconfigure(dev);
+       if (dev->bus->dma_deconfigure)
+               dev->bus->dma_deconfigure(dev);
  dma_failed:
        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
@@ -895,7 +898,8 @@ static void __device_release_driver(struct device *dev, 
struct device *parent)
                        drv->remove(dev);
device_links_driver_cleanup(dev);
-               dma_deconfigure(dev);
+               if (dev->bus->dma_deconfigure)
+                       dev->bus->dma_deconfigure(dev);
devres_release_all(dev);
                dev->driver = NULL;
diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
index 3b11835..f16bd49 100644
--- a/drivers/base/dma-mapping.c
+++ b/drivers/base/dma-mapping.c
@@ -6,11 +6,9 @@
   * Copyright (c) 2006  Tejun Heo <te...@suse.de>
   */
-#include <linux/acpi.h>
  #include <linux/dma-mapping.h>
  #include <linux/export.h>
  #include <linux/gfp.h>
-#include <linux/of_device.h>
  #include <linux/slab.h>
  #include <linux/vmalloc.h>
@@ -329,42 +327,3 @@ void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags)
        vunmap(cpu_addr);
  }
  #endif
-
-/*
- * Common configuration to enable DMA API use for a device
- */
-#include <linux/pci.h>
-
-int dma_configure(struct device *dev)
-{
-       struct device *bridge = NULL, *dma_dev = dev;
-       enum dev_dma_attr attr;
-       int ret = 0;
-
-       if (dev_is_pci(dev)) {
-               bridge = pci_get_host_bridge_device(to_pci_dev(dev));
-               dma_dev = bridge;
-               if (IS_ENABLED(CONFIG_OF) && dma_dev->parent &&
-                   dma_dev->parent->of_node)
-                       dma_dev = dma_dev->parent;
-       }
-
-       if (dma_dev->of_node) {
-               ret = of_dma_configure(dev, dma_dev->of_node);
-       } else if (has_acpi_companion(dma_dev)) {
-               attr = acpi_get_dma_attr(to_acpi_device_node(dma_dev->fwnode));
-               if (attr != DEV_DMA_NOT_SUPPORTED)
-                       ret = acpi_dma_configure(dev, attr);
-       }
-
-       if (bridge)
-               pci_put_host_bridge_device(bridge);
-
-       return ret;
-}
-
-void dma_deconfigure(struct device *dev)
-{
-       of_dma_deconfigure(dev);
-       acpi_dma_deconfigure(dev);
-}
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index f1bf7b3..adf94eb 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -1130,6 +1130,28 @@ int platform_pm_restore(struct device *dev)
#endif /* CONFIG_HIBERNATE_CALLBACKS */ +int platform_dma_configure(struct device *dev)
+{
+       enum dev_dma_attr attr;
+       int ret = 0;
+
+       if (dev->of_node) {
+               ret = of_dma_configure(dev, dev->of_node);
+       } else if (has_acpi_companion(dev)) {
+               attr = acpi_get_dma_attr(to_acpi_device_node(dev->fwnode));
+               if (attr != DEV_DMA_NOT_SUPPORTED)
+                       ret = acpi_dma_configure(dev, attr);
+       }
+
+       return ret;
+}
+
+void platform_dma_deconfigure(struct device *dev)
+{
+       of_dma_deconfigure(dev);
+       acpi_dma_deconfigure(dev);
+}
+
  static const struct dev_pm_ops platform_dev_pm_ops = {
        .runtime_suspend = pm_generic_runtime_suspend,
        .runtime_resume = pm_generic_runtime_resume,
@@ -1137,12 +1159,14 @@ int platform_pm_restore(struct device *dev)
  };
struct bus_type platform_bus_type = {
-       .name           = "platform",
-       .dev_groups     = platform_dev_groups,
-       .match          = platform_match,
-       .uevent         = platform_uevent,
-       .pm             = &platform_dev_pm_ops,
-       .force_dma      = true,
+       .name                   = "platform",
+       .dev_groups             = platform_dev_groups,
+       .match                  = platform_match,
+       .uevent                 = platform_uevent,
+       .pm                     = &platform_dev_pm_ops,
+       .dma_configure          = platform_dma_configure,
+       .dma_deconfigure        = platform_dma_deconfigure,
+       .force_dma              = true,
  };
  EXPORT_SYMBOL_GPL(platform_bus_type);
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 3bed6be..4a77814 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -18,6 +18,8 @@
  #include <linux/pm_runtime.h>
  #include <linux/suspend.h>
  #include <linux/kexec.h>
+#include <linux/acpi.h>
+#include <linux/of_device.h>
  #include "pci.h"
struct pci_dynid {
@@ -1522,19 +1524,52 @@ static int pci_bus_num_vf(struct device *dev)
        return pci_num_vf(to_pci_dev(dev));
  }
+int pci_dma_configure(struct device *dev)
+{
+       struct device *bridge, *dma_dev;

You don't need dma_dev here; see the code removed in 09515ef5ddad for how the logic originally worked.

+       enum dev_dma_attr attr;
+       int ret = 0;
+
+       bridge = pci_get_host_bridge_device(to_pci_dev(dev));
+       dma_dev = bridge;
+       if (IS_ENABLED(CONFIG_OF) && dma_dev->parent &&
+           dma_dev->parent->of_node)
+               dma_dev = dma_dev->parent;
+
+       if (dma_dev->of_node) {
+               ret = of_dma_configure(dev, dma_dev->of_node);
+       } else if (has_acpi_companion(dma_dev)) {
+               attr = acpi_get_dma_attr(to_acpi_device_node(dma_dev->fwnode));
+               if (attr != DEV_DMA_NOT_SUPPORTED)
+                       ret = acpi_dma_configure(dev, attr);
+       }
+
+       pci_put_host_bridge_device(bridge);
+
+       return ret;
+}
+
+void pci_dma_deconfigure(struct device *dev)
+{
+       of_dma_deconfigure(dev);
+       acpi_dma_deconfigure(dev);
+}
+
  struct bus_type pci_bus_type = {
-       .name           = "pci",
-       .match          = pci_bus_match,
-       .uevent         = pci_uevent,
-       .probe          = pci_device_probe,
-       .remove         = pci_device_remove,
-       .shutdown       = pci_device_shutdown,
-       .dev_groups     = pci_dev_groups,
-       .bus_groups     = pci_bus_groups,
-       .drv_groups     = pci_drv_groups,
-       .pm             = PCI_PM_OPS_PTR,
-       .num_vf         = pci_bus_num_vf,
-       .force_dma      = true,
+       .name                   = "pci",
+       .match                  = pci_bus_match,
+       .uevent                 = pci_uevent,
+       .probe                  = pci_device_probe,
+       .remove                 = pci_device_remove,
+       .shutdown               = pci_device_shutdown,
+       .dev_groups             = pci_dev_groups,
+       .bus_groups             = pci_bus_groups,
+       .drv_groups             = pci_drv_groups,
+       .pm                     = PCI_PM_OPS_PTR,
+       .num_vf                 = pci_bus_num_vf,
+       .dma_configure          = pci_dma_configure,
+       .dma_deconfigure        = pci_dma_deconfigure,
+       .force_dma              = true,
  };
  EXPORT_SYMBOL(pci_bus_type);
diff --git a/include/linux/device.h b/include/linux/device.h
index b093405..9b2dcf6 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -88,6 +88,9 @@ extern int __must_check bus_create_file(struct bus_type *,
   * @resume:   Called to bring a device on this bus out of sleep mode.
   * @num_vf:   Called to find out how many virtual functions a device on this
   *            bus supports.
+ * @dma_configure:     Called to setup DMA configuration on a device on
+                       this bus.
+ * @dma_deconfigure:   Called to tear down the DMA configuration.
   * @pm:               Power management operations of this bus, callback the 
specific
   *            device driver's pm-ops.
   * @iommu_ops:  IOMMU specific operations for this bus, used to attach IOMMU
@@ -130,6 +133,9 @@ struct bus_type {
int (*num_vf)(struct device *dev); + int (*dma_configure)(struct device *dev);
+       void (*dma_deconfigure)(struct device *dev);

Seeing it laid out in the patch, I really don't think we need a deconfigure callback like this - the fact that we're just copy-pasting the existing implementation everywhere is a big hint, but more conceptually I can't see a good reason for it to ever need bus-specific behaviour in the same way that configure does.

Maybe that means we keep dma_configure() around for the sake of symmetry, but just reduce it to:

int dma_configure(struct device *dev)
{
        if (dev->bus->dma_configure)
                return dev->bus->dma_configure(dev);
        return 0;
}

Realistically though, dma_deconfigure() only exists for the sake of calling arch_teardown_dma_ops(), and that only really exists for the sake of the old ARM IOMMU code, so I'm not inclined to pretend it's anywhere near as important as the dma_configure() path in design terms.

Robin.

+
        const struct dev_pm_ops *pm;
const struct iommu_ops *iommu_ops;
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index eb9eab4..039224b 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -761,18 +761,6 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
  }
  #endif /* CONFIG_HAVE_GENERIC_DMA_COHERENT */
-#ifdef CONFIG_HAS_DMA
-int dma_configure(struct device *dev);
-void dma_deconfigure(struct device *dev);
-#else
-static inline int dma_configure(struct device *dev)
-{
-       return 0;
-}
-
-static inline void dma_deconfigure(struct device *dev) {}
-#endif
-
  /*
   * Managed DMA API
   */

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