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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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