Re: [RFC/NOT FOR MERGING 2/3] serial: omap: remove hwmod dependency

[Tony Lindgren <tony@atomide.com>]

* Paul Walmsley <paul@pwsan.com> [130214 13:44]:
> Hi,
> 
> On Thu, 14 Feb 2013, Paul Walmsley wrote:
> 
> > So instead of something bus-specific like that, a better way would be to 
> > use something like:
> > 
> > va = dev->bus->ioremap( ... );
> > va = dev->bus->iounmap( ... );
> 
> Something like this is what I was thinking.  Obviously there would be more
> patches needed, for the various arches, etc.; and I'm not convinced that
> the function pointer init is done at the right time yet. Comments welcome.
> 
> 
> - Paul
> 
> 
> From: Paul Walmsley <paul@pwsan.com>
> Date: Thu, 14 Feb 2013 13:49:58 -0700
> Subject: [PATCH] EXPERIMENTAL: device/ARM: allow buses to override ioremap*()
>  and iounmap()
> 
> On some hardware, such as OMAP, the bus abstraction code needs to call
> ioremap(), since some SoC-integration registers are located in the
> device address space.  But generic device drivers should be able to
> call ioremap() from driver code, for the majority of situations where
> this isn't necessary.  This experimental patch allows Linux bus abstraction
> code to override all of the ioremap*() and iounmap() functions.  In the OMAP
> case, this would be used to return the previously-mapped address range from
> the bus code, when called for the device's register area.  This would avoid
> a duplicate TLB mapping for that space.
> 
> This might also be useful as a generic replacement for pci_ioremap_bar().
> 
> Compile-tested only.

The other option could be to allow custom ioremap function pointers 
based on address range in __arm_ioremap_pfn_caller() the same way as
the SoC specific static mappings are allowed. That would require adding
a function pointer to struct map_desc.

Maybe that would do the trick?

Regards,

Tony

> ---
>  arch/arm/include/asm/io.h |   10 +++++-----
>  arch/arm/mm/ioremap.c     |   30 ++++++++++++++++++++++++++++++
>  arch/arm/mm/mmu.c         |    8 ++++++++
>  include/linux/device.h    |   26 ++++++++++++++++++++++++++
>  4 files changed, 69 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
> index 652b560..22cc085 100644
> --- a/arch/arm/include/asm/io.h
> +++ b/arch/arm/include/asm/io.h
> @@ -325,11 +325,11 @@ extern void _memset_io(volatile void __iomem *, int, size_t);
>   * Documentation/io-mapping.txt.
>   *
>   */
> -#define ioremap(cookie,size)		__arm_ioremap((cookie), (size), MT_DEVICE)
j> -#define ioremap_nocache(cookie,size)	__arm_ioremap((cookie), (size), MT_DEVICE)
> -#define ioremap_cached(cookie,size)	__arm_ioremap((cookie), (size), MT_DEVICE_CACHED)
> -#define ioremap_wc(cookie,size)		__arm_ioremap((cookie), (size), MT_DEVICE_WC)
> -#define iounmap				__arm_iounmap
> +extern void __iomem *ioremap(unsigned long cookie, size_t size);
> +extern void __iomem *ioremap_nocache(unsigned long cookie, size_t size);
> +extern void __iomem *ioremap_cached(unsigned long cookie, size_t size);
> +extern void __iomem *ioremap_wc(unsigned long cookie, size_t size);
> +extern void iounmap(volatile void __iomem *va);
>  
>  /*
>   * io{read,write}{8,16,32} macros
> diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
> index 88fd86c..6507e69 100644
> --- a/arch/arm/mm/ioremap.c
> +++ b/arch/arm/mm/ioremap.c
> @@ -398,3 +398,33 @@ int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr)
>  }
>  EXPORT_SYMBOL_GPL(pci_ioremap_io);
>  #endif
> +
> +void __iomem *ioremap(unsigned long cookie, size_t size)
> +{
> +	return __arm_ioremap(cookie, size, MT_DEVICE);
> +}
> +EXPORT_SYMBOL(ioremap);
> +
> +void __iomem *ioremap_nocache(unsigned long cookie, size_t size)
> +{
> +	return __arm_ioremap(cookie, size, MT_DEVICE);
> +}
> +EXPORT_SYMBOL(ioremap_nocache);
> +
> +void __iomem *ioremap_cached(unsigned long cookie, size_t size)
> +{
> +	return __arm_ioremap(cookie, size, MT_DEVICE_CACHED);
> +}
> +EXPORT_SYMBOL(ioremap_cached);
> +
> +void __iomem *ioremap_wc(unsigned long cookie, size_t size)
> +{
> +	return __arm_ioremap(cookie, size, MT_DEVICE_WC);
> +}
> +EXPORT_SYMBOL(ioremap_wc);
> +
> +void iounmap(volatile void __iomem *va)
> +{
> +	return __arm_iounmap(va);
> +}
> +EXPORT_SYMBOL(iounmap);
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index ce328c7..303dba0 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -17,6 +17,7 @@
>  #include <linux/fs.h>
>  #include <linux/vmalloc.h>
>  #include <linux/sizes.h>
> +#include <linux/platform_device.h>
>  
>  #include <asm/cp15.h>
>  #include <asm/cputype.h>
> @@ -28,6 +29,7 @@
>  #include <asm/highmem.h>
>  #include <asm/system_info.h>
>  #include <asm/traps.h>
> +#include <asm/io.h>
>  
>  #include <asm/mach/arch.h>
>  #include <asm/mach/map.h>
> @@ -1246,4 +1248,10 @@ void __init paging_init(struct machine_desc *mdesc)
>  
>  	empty_zero_page = virt_to_page(zero_page);
>  	__flush_dcache_page(NULL, empty_zero_page);
> +
> +	platform_bus_type.ioremap = ioremap;
> +	platform_bus_type.ioremap_nocache = ioremap_nocache;
> +	platform_bus_type.ioremap_cached = ioremap_cached;
> +	platform_bus_type.ioremap_wc = ioremap_wc;
> +	platform_bus_type.iounmap = iounmap;
>  }
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 43dcda9..48c35e2 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -71,6 +71,26 @@ extern void bus_remove_file(struct bus_type *, struct bus_attribute *);
>   * @shutdown:	Called at shut-down time to quiesce the device.
>   * @suspend:	Called when a device on this bus wants to go to sleep mode.
>   * @resume:	Called to bring a device on this bus out of sleep mode.
> + * @ioremap:	Function pointer returning a virtual address used to
> + *		interact with a device on this bus.  Generally
> + *		implemented via @ioremap_nocache.
> + * @ioremap_nocache: Function pointer returning a virtual address used to
> + *		interact with a device on this bus.  Reads and writes
> + *		to the returned address space are not cached by the
> + *		CPU, so are suitable for memory-mapped I/O regions.
> + * @ioremap_cached: Function pointer returning a virtual address used to
> + *		interact with private memory located on this bus.  Reads and
> + *		writes to the returned address space may be cached by the
> + *		CPU, so this is suitable for I/O-mapped memory where all
> + *		accesses are via the same cache.
> + * @ioremap_wc: Function pointer returning a virtual address used to
> + *		interact with memory located on this bus.  Writes to
> + *		the returned address space may be combined by the CPU,
> + *		so this is suitable for I/O-mapped memory such as
> + *		framebuffers.
> + * @iounmap:	Function pointer called to indicate that a caller is done
> + *		with the virtual address mapping returned by @ioremap,
> + *		@ioremap_nocache, @ioremap_cached, or @ioremap_wc.
>   * @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
> @@ -105,6 +125,12 @@ struct bus_type {
>  	int (*suspend)(struct device *dev, pm_message_t state);
>  	int (*resume)(struct device *dev);
>  
> +	void __iomem *(*ioremap)(unsigned long phys_addr, size_t size);
> +	void __iomem *(*ioremap_nocache)(unsigned long phys_addr, size_t size);
> +	void __iomem *(*ioremap_cached)(unsigned long phys_addr, size_t size);
> +	void __iomem *(*ioremap_wc)(unsigned long phys_addr, size_t size);
> +	void (*iounmap)(volatile void __iomem *va);
> +
>  	const struct dev_pm_ops *pm;
>  
>  	struct iommu_ops *iommu_ops;
> -- 
> 1.7.10.4
>