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    SubjectRe: [PATCH] dma-mapping: move dma configuration to bus infrastructure
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    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.gupta@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 <teheo@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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