Hi Arnd,
On Sat, Mar 15, 2025 at 11:59:06AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> 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@xxxxxxxx>
> ---
> 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
