RE: [PATCH] dma-mapping: move dma configuration to bus infrastructure

[Nipun Gupta]

> -----Original Message-----
> From: Robin Murphy [mailto:robin.murphy@xxxxxxx]
> Sent: Tuesday, March 13, 2018 17:06
> 
> 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.

Okay.

>
> > The change also updates the PCI, Platform and ACPI bus to use
> > new introduced callbacks.
> >
> > Signed-off-by: Nipun Gupta <nipun.gupta@xxxxxxx>
> > ---
> >   - This patch is based on the comments on:
> >
> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwo
> rk.kernel.org%2Fpatch%2F10259087%2F&data=02%7C01%7Cnipun.gupta%40nxp.com%7
> Cc541100ecb944e7650a408d588d69ab0%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7
> C0%7C636565377665676631&sdata=k2Xjn5B1GECx4UjCg9tChOpOrD3NPM7BkzIXLLSv3rI%
> 3D&reserved=0
> >   - 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.

I think dma_common_configure() having this as the common code seems pretty
Decent. All the busses will probably call this API.

> 
> > +
> > +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.

Agree. We will also need to pass a force_dma flag in of_dma_configure() as
Christoph suggests. Ill update this.

> 
> >   };
> >
> >   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@xxxxxxx>
> >    */
> >
> > -#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.

Okay. I will have a look in this commit id.

> 
> > +	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.

Yes, I will remove dma_deconfigure callback.

Thanks,
Nipun

> 
> 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
> >    */
> >