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s390: Remove ioremap_wt() and pgprot_writethrough()

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It turns out that while s390 architecture calls its memory-I/O mapping
variants write-through and write-back the implementation of ioremap_wt()
and pgprot_writethrough() does not match Linux notion of ioremap_wt().

In particular Linux expects ioremap_wt() to be weaker still than
ioremap_wc(), allowing not just gathering and re-ordering but also reads
to be served from cache. Instead s390's implementation is equivalent to
normal ioremap() while its ioremap_wc() allows re-ordering.

Note that there are no known users of ioremap_wt() on s390 and the
resulting behavior is in line with asm-generic defining ioremap_wt() as
ioremap(), if undefined, so no breakage is expected.

As s390 does not have a mapping type matching the Linux notion of
ioremap_wt() and pgprot_writethrough(), simply drop them and rely on the
asm-generic fallbacks instead.

Fixes: b02002cc4c ("s390/pci: Implement ioremap_wc/prot() with MIO")
Fixes: b43b3fff04 ("s390: mm: convert to GENERIC_IOREMAP")
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Niklas Schnelle
2025-02-21 12:51:48 +01:00
committed by Vasily Gorbik
parent 08d95a12cd
commit c94bff63e4
3 changed files with 0 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/s390/include/asm/io.h
View File

@@ -34,8 +34,6 @@ void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr);
#define ioremap_wc(addr, size) \
ioremap_prot((addr), (size), pgprot_val(pgprot_writecombine(PAGE_KERNEL)))
#define ioremap_wt(addr, size) \
ioremap_prot((addr), (size), pgprot_val(pgprot_writethrough(PAGE_KERNEL)))
static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
{

3
arch/s390/include/asm/pgtable.h
View File

@@ -1403,9 +1403,6 @@ void gmap_pmdp_idte_global(struct mm_struct *mm, unsigned long vmaddr);
#define pgprot_writecombine pgprot_writecombine
pgprot_t pgprot_writecombine(pgprot_t prot);
#define pgprot_writethrough pgprot_writethrough
pgprot_t pgprot_writethrough(pgprot_t prot);
#define PFN_PTE_SHIFT PAGE_SHIFT
/*

10
arch/s390/mm/pgtable.c
View File

@@ -36,16 +36,6 @@ pgprot_t pgprot_writecombine(pgprot_t prot)
}
EXPORT_SYMBOL_GPL(pgprot_writecombine);
pgprot_t pgprot_writethrough(pgprot_t prot)
{
/*
* mio_wb_bit_mask may be set on a different CPU, but it is only set
* once at init and only read afterwards.
*/
return __pgprot(pgprot_val(prot) & ~mio_wb_bit_mask);
}
EXPORT_SYMBOL_GPL(pgprot_writethrough);
static inline void ptep_ipte_local(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, int nodat)
{