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[PATCH 5/6] mips: drop GENERIC_IOMAP wrapper

Arnd Bergmann posted 6 patches 9 months, 1 week ago
[PATCH 5/6] mips: drop GENERIC_IOMAP wrapper
Posted by Arnd Bergmann 9 months, 1 week ago 
From: Arnd Bergmann <arnd@arndb.de>

All PIO on MIPS platforms is memory mapped, so there is no benefit in
the lib/iomap.c wrappers that switch between inb/outb and readb/writeb
style accessses.

In fact, the '#define PIO_RESERVED 0' setting completely disables
the GENERIC_IOMAP functionality, and the '#define PIO_OFFSET
mips_io_port_base' setting is based on a misunderstanding of what the
offset is meant to do.

MIPS started using GENERIC_IOMAP in 2018 with commit b962aeb02205 ("MIPS:
Use GENERIC_IOMAP") replacing a simple custom implementation of the same
interfaces, but at the time the asm-generic/io.h version was not usable
yet. Since the header is now always included, it's now possible to go
back to the even simpler version.

Use the normal GENERIC_PCI_IOMAP functionality for all mips platforms
without the hacky GENERIC_IOMAP, and provide a custom pci_iounmap()
for the CONFIG_PCI_DRIVERS_LEGACY case to ensure the I/O port base never
gets unmapped.

The readsl() prototype needs an extra 'const' keyword to make it
compatible with the generic ioread32_rep() alias.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/mips/Kconfig          |  2 +-
 arch/mips/include/asm/io.h | 21 ++++++++-------------
 arch/mips/lib/iomap-pci.c  |  9 +++++++++
 3 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 1924f2d83932..2a2120a6d852 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -38,7 +38,6 @@ config MIPS
 	select GENERIC_CMOS_UPDATE
 	select GENERIC_CPU_AUTOPROBE
 	select GENERIC_GETTIMEOFDAY
-	select GENERIC_IOMAP
 	select GENERIC_IRQ_PROBE
 	select GENERIC_IRQ_SHOW
 	select GENERIC_ISA_DMA if EISA
@@ -47,6 +46,7 @@ config MIPS
 	select GENERIC_LIB_CMPDI2
 	select GENERIC_LIB_LSHRDI3
 	select GENERIC_LIB_UCMPDI2
+	select GENERIC_PCI_IOMAP
 	select GENERIC_SCHED_CLOCK if !CAVIUM_OCTEON_SOC
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_IDLE_POLL_SETUP
diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h
index 0bddb568af7c..1fe56d1870a6 100644
--- a/arch/mips/include/asm/io.h
+++ b/arch/mips/include/asm/io.h
@@ -66,17 +66,6 @@ static inline void set_io_port_base(unsigned long base)
 	mips_io_port_base = base;
 }
 
-/*
- * Provide the necessary definitions for generic iomap. We make use of
- * mips_io_port_base for iomap(), but we don't reserve any low addresses for
- * use with I/O ports.
- */
-
-#define HAVE_ARCH_PIO_SIZE
-#define PIO_OFFSET	mips_io_port_base
-#define PIO_MASK	IO_SPACE_LIMIT
-#define PIO_RESERVED	0x0UL
-
 /*
  * Enforce in-order execution of data I/O.  In the MIPS architecture
  * these are equivalent to corresponding platform-specific memory
@@ -397,8 +386,8 @@ static inline void writes##bwlq(volatile void __iomem *mem,		\
 	}								\
 }									\
 									\
-static inline void reads##bwlq(volatile void __iomem *mem, void *addr,	\
-			       unsigned int count)			\
+static inline void reads##bwlq(const volatile void __iomem *mem,	\
+			       void *addr, unsigned int count)		\
 {									\
 	volatile type *__addr = addr;					\
 									\
@@ -555,6 +544,12 @@ extern void (*_dma_cache_inv)(unsigned long start, unsigned long size);
 
 void __ioread64_copy(void *to, const void __iomem *from, size_t count);
 
+#ifdef CONFIG_PCI_DRIVERS_LEGACY
+struct pci_dev;
+void pci_iounmap(struct pci_dev *dev, void __iomem *addr);
+#define pci_iounmap pci_iounmap
+#endif
+
 #include <asm-generic/io.h>
 
 static inline void *isa_bus_to_virt(unsigned long address)
diff --git a/arch/mips/lib/iomap-pci.c b/arch/mips/lib/iomap-pci.c
index a9cb28813f0b..2f82c776c6d0 100644
--- a/arch/mips/lib/iomap-pci.c
+++ b/arch/mips/lib/iomap-pci.c
@@ -43,4 +43,13 @@ void __iomem *__pci_ioport_map(struct pci_dev *dev,
 	return (void __iomem *) (ctrl->io_map_base + port);
 }
 
+void pci_iounmap(struct pci_dev *dev, void __iomem *addr)
+{
+	struct pci_controller *ctrl = dev->bus->sysdata;
+	void __iomem *base = (void __iomem *)ctrl->io_map_base;
+
+	if (addr < base || addr > (base + resource_size(ctrl->io_resource)))
+		iounmap(addr);
+}
+
 #endif /* CONFIG_PCI_DRIVERS_LEGACY */
-- 
2.39.5
Re: [PATCH 5/6] mips: drop GENERIC_IOMAP wrapper
Posted by Nathan Chancellor 9 months ago 
Hi Arnd,

On Sat, Mar 15, 2025 at 11:59:06AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> All PIO on MIPS platforms is memory mapped, so there is no benefit in
> the lib/iomap.c wrappers that switch between inb/outb and readb/writeb
> style accessses.
> 
> In fact, the '#define PIO_RESERVED 0' setting completely disables
> the GENERIC_IOMAP functionality, and the '#define PIO_OFFSET
> mips_io_port_base' setting is based on a misunderstanding of what the
> offset is meant to do.
> 
> MIPS started using GENERIC_IOMAP in 2018 with commit b962aeb02205 ("MIPS:
> Use GENERIC_IOMAP") replacing a simple custom implementation of the same
> interfaces, but at the time the asm-generic/io.h version was not usable
> yet. Since the header is now always included, it's now possible to go
> back to the even simpler version.
> 
> Use the normal GENERIC_PCI_IOMAP functionality for all mips platforms
> without the hacky GENERIC_IOMAP, and provide a custom pci_iounmap()
> for the CONFIG_PCI_DRIVERS_LEGACY case to ensure the I/O port base never
> gets unmapped.
> 
> The readsl() prototype needs an extra 'const' keyword to make it
> compatible with the generic ioread32_rep() alias.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  arch/mips/Kconfig          |  2 +-
>  arch/mips/include/asm/io.h | 21 ++++++++-------------
>  arch/mips/lib/iomap-pci.c  |  9 +++++++++
>  3 files changed, 18 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 1924f2d83932..2a2120a6d852 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -38,7 +38,6 @@ config MIPS
>  	select GENERIC_CMOS_UPDATE
>  	select GENERIC_CPU_AUTOPROBE
>  	select GENERIC_GETTIMEOFDAY
> -	select GENERIC_IOMAP
>  	select GENERIC_IRQ_PROBE
>  	select GENERIC_IRQ_SHOW
>  	select GENERIC_ISA_DMA if EISA
> @@ -47,6 +46,7 @@ config MIPS
>  	select GENERIC_LIB_CMPDI2
>  	select GENERIC_LIB_LSHRDI3
>  	select GENERIC_LIB_UCMPDI2
> +	select GENERIC_PCI_IOMAP
>  	select GENERIC_SCHED_CLOCK if !CAVIUM_OCTEON_SOC
>  	select GENERIC_SMP_IDLE_THREAD
>  	select GENERIC_IDLE_POLL_SETUP
> diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h
> index 0bddb568af7c..1fe56d1870a6 100644
> --- a/arch/mips/include/asm/io.h
> +++ b/arch/mips/include/asm/io.h
> @@ -66,17 +66,6 @@ static inline void set_io_port_base(unsigned long base)
>  	mips_io_port_base = base;
>  }
>  
> -/*
> - * Provide the necessary definitions for generic iomap. We make use of
> - * mips_io_port_base for iomap(), but we don't reserve any low addresses for
> - * use with I/O ports.
> - */
> -
> -#define HAVE_ARCH_PIO_SIZE
> -#define PIO_OFFSET	mips_io_port_base
> -#define PIO_MASK	IO_SPACE_LIMIT
> -#define PIO_RESERVED	0x0UL
> -
>  /*
>   * Enforce in-order execution of data I/O.  In the MIPS architecture
>   * these are equivalent to corresponding platform-specific memory
> @@ -397,8 +386,8 @@ static inline void writes##bwlq(volatile void __iomem *mem,		\
>  	}								\
>  }									\
>  									\
> -static inline void reads##bwlq(volatile void __iomem *mem, void *addr,	\
> -			       unsigned int count)			\
> +static inline void reads##bwlq(const volatile void __iomem *mem,	\
> +			       void *addr, unsigned int count)		\
>  {									\
>  	volatile type *__addr = addr;					\
>  									\
> @@ -555,6 +544,12 @@ extern void (*_dma_cache_inv)(unsigned long start, unsigned long size);
>  
>  void __ioread64_copy(void *to, const void __iomem *from, size_t count);
>  
> +#ifdef CONFIG_PCI_DRIVERS_LEGACY
> +struct pci_dev;
> +void pci_iounmap(struct pci_dev *dev, void __iomem *addr);
> +#define pci_iounmap pci_iounmap
> +#endif
> +
>  #include <asm-generic/io.h>
>  
>  static inline void *isa_bus_to_virt(unsigned long address)
> diff --git a/arch/mips/lib/iomap-pci.c b/arch/mips/lib/iomap-pci.c
> index a9cb28813f0b..2f82c776c6d0 100644
> --- a/arch/mips/lib/iomap-pci.c
> +++ b/arch/mips/lib/iomap-pci.c
> @@ -43,4 +43,13 @@ void __iomem *__pci_ioport_map(struct pci_dev *dev,
>  	return (void __iomem *) (ctrl->io_map_base + port);
>  }
>  
> +void pci_iounmap(struct pci_dev *dev, void __iomem *addr)
> +{
> +	struct pci_controller *ctrl = dev->bus->sysdata;
> +	void __iomem *base = (void __iomem *)ctrl->io_map_base;
> +
> +	if (addr < base || addr > (base + resource_size(ctrl->io_resource)))
> +		iounmap(addr);
> +}
> +
>  #endif /* CONFIG_PCI_DRIVERS_LEGACY */
> -- 
> 2.39.5
> 

This change as commit 976bf3aec388 ("mips: drop GENERIC_IOMAP wrapper") in
-next introduces new instances of -Wnull-pointer-arithmetic when building
certain mips configurations with clang.

  $ make -skj"$(nproc)" ARCH=mips LLVM=1 mrproper malta_defconfig init/main.o
  ...
  In file included from init/main.c:17:
  In file included from include/linux/module.h:17:
  In file included from include/linux/kmod.h:9:
  In file included from include/linux/umh.h:4:
  In file included from include/linux/gfp.h:7:
  In file included from include/linux/mmzone.h:22:
  In file included from include/linux/mm_types.h:5:
  In file included from include/linux/mm_types_task.h:14:
  In file included from arch/mips/include/asm/page.h:181:
  In file included from arch/mips/include/asm/io.h:553:
  include/asm-generic/io.h:1175:55: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
   1175 |         return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
        |                                                   ~~~~~~~~~~ ^
  1 warning generated.

Cheers,
Nathan
Re: [PATCH 5/6] mips: drop GENERIC_IOMAP wrapper
Posted by Arnd Bergmann 9 months ago 
On Tue, Mar 18, 2025, at 21:39, Nathan Chancellor wrote:
> On Sat, Mar 15, 2025 at 11:59:06AM +0100, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@arndb.de>
>> diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h

>>  void __ioread64_copy(void *to, const void __iomem *from, size_t count);
>>  
>> +#ifdef CONFIG_PCI_DRIVERS_LEGACY
>> +struct pci_dev;
>> +void pci_iounmap(struct pci_dev *dev, void __iomem *addr);
>> +#define pci_iounmap pci_iounmap
>> +#endif
>> +
>>  #include <asm-generic/io.h>
>>  
>>  static inline void *isa_bus_to_virt(unsigned long address)
>> diff --git a/arch/mips/lib/iomap-pci.c b/arch/mips/lib/iomap-pci.c
>> index a9cb28813f0b..2f82c776c6d0 100644
>> --- a/arch/mips/lib/iomap-pci.c
>> +++ b/arch/mips/lib/iomap-pci.c
>> @@ -43,4 +43,13 @@ void __iomem *__pci_ioport_map(struct pci_dev *dev,
>>  	return (void __iomem *) (ctrl->io_map_base + port);
>>  }
>>  
>> +void pci_iounmap(struct pci_dev *dev, void __iomem *addr)
>> +{
>> +	struct pci_controller *ctrl = dev->bus->sysdata;
>> +	void __iomem *base = (void __iomem *)ctrl->io_map_base;
>> +
>> +	if (addr < base || addr > (base + resource_size(ctrl->io_resource)))
>> +		iounmap(addr);
>> +}
>> +
>>  #endif /* CONFIG_PCI_DRIVERS_LEGACY */
>> -- 
>> 2.39.5
>> 
>
> This change as commit 976bf3aec388 ("mips: drop GENERIC_IOMAP wrapper") in
> -next introduces new instances of -Wnull-pointer-arithmetic when building
> certain mips configurations with clang.
>

Thanks for the report, I missed that the generic ioport_map() function
is missing the PCI_IOBASE macro, we should probably remove that from
the asm-generic/io.h header and require architectures to define it
themselves, since the NULL fallback is pretty much always wrong.

There is also a type mismatch between the MIPS
PCI_IOBASE/mips_io_port_base and the one that asm-generic/io.h
expects, so I had to add a couple of extra typecasts, which
makes it rather ugly, but the change below seems to work.

     Arnd

diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h
index 1fe56d1870a6..78c6573f91f2 100644
--- a/arch/mips/include/asm/io.h
+++ b/arch/mips/include/asm/io.h
@@ -544,12 +544,16 @@ extern void (*_dma_cache_inv)(unsigned long start, unsigned long size);
 
 void __ioread64_copy(void *to, const void __iomem *from, size_t count);
 
-#ifdef CONFIG_PCI_DRIVERS_LEGACY
+#if defined(CONFIG_PCI) && defined(CONFIG_PCI_DRIVERS_LEGACY)
 struct pci_dev;
 void pci_iounmap(struct pci_dev *dev, void __iomem *addr);
 #define pci_iounmap pci_iounmap
 #endif
 
+#ifndef PCI_IOBASE
+#define PCI_IOBASE ((void __iomem *)mips_io_port_base)
+#endif
+
 #include <asm-generic/io.h>
 
 static inline void *isa_bus_to_virt(unsigned long address)
diff --git a/arch/mips/include/asm/mach-loongson64/spaces.h b/arch/mips/include/asm/mach-loongson64/spaces.h
index ce04e998a37b..dbd26db5f2c5 100644
--- a/arch/mips/include/asm/mach-loongson64/spaces.h
+++ b/arch/mips/include/asm/mach-loongson64/spaces.h
@@ -7,9 +7,10 @@
 #endif /* CONFIG_64BIT */
 
 /* Skip 128k to trap NULL pointer dereferences */
-#define PCI_IOBASE	_AC(0xc000000000000000 + SZ_128K, UL)
+#define PCI_PORT_BASE	_AC(0xc000000000000000 + SZ_128K, UL)
+#define PCI_IOBASE	(void __iomem *)PCI_PORT_BASE
 #define PCI_IOSIZE	SZ_16M
-#define MAP_BASE	(PCI_IOBASE + PCI_IOSIZE)
+#define MAP_BASE	(PCI_PORT_BASE + PCI_IOSIZE)
 
 #define IO_SPACE_LIMIT  (PCI_IOSIZE - 1)
 
diff --git a/arch/mips/include/asm/mach-ralink/spaces.h b/arch/mips/include/asm/mach-ralink/spaces.h
index a9f0570d0f04..a63d106c89c6 100644
--- a/arch/mips/include/asm/mach-ralink/spaces.h
+++ b/arch/mips/include/asm/mach-ralink/spaces.h
@@ -2,7 +2,7 @@
 #ifndef __ASM_MACH_RALINK_SPACES_H_
 #define __ASM_MACH_RALINK_SPACES_H_
 
-#define PCI_IOBASE	mips_io_port_base
+#define PCI_IOBASE	(void __iomem *)mips_io_port_base
 #define PCI_IOSIZE	SZ_64K
 #define IO_SPACE_LIMIT	(PCI_IOSIZE - 1)
 
diff --git a/arch/mips/loongson64/init.c b/arch/mips/loongson64/init.c
index a35dd7311795..b9f90f33fc9a 100644
--- a/arch/mips/loongson64/init.c
+++ b/arch/mips/loongson64/init.c
@@ -128,7 +128,7 @@ void __init prom_init(void)
 	}
 
 	/* init base address of io space */
-	set_io_port_base(PCI_IOBASE);
+	set_io_port_base((unsigned long)PCI_IOBASE);
 
 	if (loongson_sysconf.early_config)
 		loongson_sysconf.early_config();
@@ -178,7 +178,7 @@ static int __init add_legacy_isa_io(struct fwnode_handle *fwnode, resource_size_
 		return -EINVAL;
 	}
 
-	vaddr = PCI_IOBASE + range->io_start;
+	vaddr = (unsigned long)PCI_IOBASE + range->io_start;
 
 	vmap_page_range(vaddr, vaddr + size, hw_start, pgprot_device(PAGE_KERNEL));
Re: [PATCH 5/6] mips: drop GENERIC_IOMAP wrapper
Posted by Nathan Chancellor 9 months ago 
On Tue, Mar 18, 2025 at 10:13:35PM +0100, Arnd Bergmann wrote:
> Thanks for the report, I missed that the generic ioport_map() function
> is missing the PCI_IOBASE macro, we should probably remove that from
> the asm-generic/io.h header and require architectures to define it
> themselves, since the NULL fallback is pretty much always wrong.
> 
> There is also a type mismatch between the MIPS
> PCI_IOBASE/mips_io_port_base and the one that asm-generic/io.h
> expects, so I had to add a couple of extra typecasts, which
> makes it rather ugly, but the change below seems to work.

Thanks, that does make the -Wnull-pointer-arithmetic warnings disappear.
That build still fails in next-20250319 (which includes that change) at
the end with:

  $ make -skj"$(nproc)" ARCH=mips CROSS_COMPILE=mips-linux- mrproper malta_defconfig all
  ERROR: modpost: "pci_iounmap" [drivers/net/wireless/intel/ipw2x00/ipw2100.ko] undefined!

which appears related to this original change.

Cheers,
Nathan
Re: [PATCH 5/6] mips: drop GENERIC_IOMAP wrapper
Posted by Arnd Bergmann 9 months ago 
On Wed, Mar 19, 2025, at 18:30, Nathan Chancellor wrote:
> On Tue, Mar 18, 2025 at 10:13:35PM +0100, Arnd Bergmann wrote:
>> Thanks for the report, I missed that the generic ioport_map() function
>> is missing the PCI_IOBASE macro, we should probably remove that from
>> the asm-generic/io.h header and require architectures to define it
>> themselves, since the NULL fallback is pretty much always wrong.
>> 
>> There is also a type mismatch between the MIPS
>> PCI_IOBASE/mips_io_port_base and the one that asm-generic/io.h
>> expects, so I had to add a couple of extra typecasts, which
>> makes it rather ugly, but the change below seems to work.
>
> Thanks, that does make the -Wnull-pointer-arithmetic warnings disappear.
> That build still fails in next-20250319 (which includes that change) at
> the end with:
>
>   $ make -skj"$(nproc)" ARCH=mips CROSS_COMPILE=mips-linux- mrproper 
> malta_defconfig all
>   ERROR: modpost: "pci_iounmap" 
> [drivers/net/wireless/intel/ipw2x00/ipw2100.ko] undefined!
>
> which appears related to this original change.

Right, I had seen and fixed a problem like this in an earlier
version, but forgot the EXPORT_SYMBOL on the legacy host version.

Fixed it better now.

      Arnd

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