Re: [Linux-ia64] Re: Write Combining (Write Coalescing) on memory mapped

Steffen Persvold
2001-09-10T19:29:17Z

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David Mosberger wrote:
>
> >>>>> On Mon, 10 Sep 2001 17:26:47 +0200, Steffen Persvold <sp@scali.no> said:
>
> Steffen> This is what my original post (which included a patch)
> Steffen> tried to do, but I didn't get it too work. I know you gave
> Steffen> me feedback on this David, saying that it just may need
> Steffen> some debugging. Does anyone on the list have the time to
> Steffen> just look through the patch and try to analyze what's going
> Steffen> wrong (or maybe just give me some hints on what to look
> Steffen> for) ?
>
> I don't, not in the near future at least.
>
> There is nothing magical about debugging on ia64. Just use the normal
> techniques: try to narrow down what's triggering the problem, e.g.,
> via binary search, printk, etc. A kdb patch is also available.
>

Yep, I know. But I managed to solve it without the use of kdb. It was just a
question of using the right __pgprot flags. I've attached a new patch, it's made
against 2.4.4 but it also applies cleanly to a vanilla 2.4.9 tree. I guess this
means that we don't have to use the uncached region 6 anymore; ioremap() could
be modified to use __ia64_ioremap() with the _PAGE_MA_WC attribute and
ioremap_nocache() to with the _PAGE_MA_UC attribute. Any comments ?

I sure hope that this is patch that you would consider going into the main ia64
tree.

Regards,
--
Steffen Persvold | Scali Computer AS | Try out the world's best
mailto:sp@scali.no | http://www.scali.com | performing MPI implementation:
Tel: (+47) 2262 8950 | Olaf Helsets vei 6 | - ScaMPI 1.12.2 -
Fax: (+47) 2262 8951 | N0621 Oslo, NORWAY | >300MBytes/s and <4uS latency

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--- linux-2.4.4/arch/ia64/mm/Makefile.~1~ Thu Jan 4 21:50:17 2001
+++ linux-2.4.4/arch/ia64/mm/Makefile Sat Aug 11 21:20:03 2001
@@ -9,6 +9,6 @@

O_TARGET := mm.o

-obj-y := init.o fault.o tlb.o extable.o
+obj-y := init.o fault.o ioremap.o tlb.o extable.o

include $(TOPDIR)/Rules.make
--- linux-2.4.4/arch/ia64/mm/ioremap.c.~1~ Tue May 5 22:32:27 1998
+++ linux-2.4.4/arch/ia64/mm/ioremap.c Sat Aug 11 23:57:31 2001
@@ -0,0 +1,154 @@
+/*
+ * arch/s390/mm/ioremap.c
+ *
+ * IA64 version
+ * Copyright (C) 2001 Scali AS
+ * Author(s): Steffen Persvold (sp@scali.com)
+ *
+ * Derived from "arch/i386/mm/ioremap.c"
+ * (C) Copyright 1995 1996 Linus Torvalds
+ *
+ * Re-map IO memory to kernel address space so that we can access it.
+ */
+
+#include <linux/vmalloc.h>
+#include <asm/io.h>
+#include <asm/pgalloc.h>
+
+static inline void remap_area_pte(pte_t * pte, unsigned long address, unsigned long size,
+ unsigned long phys_addr, unsigned long flags)
+{
+ unsigned long end;
+
+ address &= ~PMD_MASK;
+ end = address + size;
+ if (end > PMD_SIZE)
+ end = PMD_SIZE;
+ if (address >= end)
+ BUG();
+ do {
+ if (!pte_none(*pte)) {
+ printk("remap_area_pte: page already exists\n");
+ BUG();
+ }
+ set_pte(pte, mk_pte_phys(phys_addr, __pgprot(__DIRTY_BITS | _PAGE_PL_0 |
+ _PAGE_AR_RWX | (flags & _PAGE_MA_MASK))));
+ address += PAGE_SIZE;
+ phys_addr += PAGE_SIZE;
+ pte++;
+ } while (address && (address < end));
+}
+
+static inline int remap_area_pmd(pmd_t * pmd, unsigned long address, unsigned long size,
+ unsigned long phys_addr, unsigned long flags)
+{
+ unsigned long end;
+
+ address &= ~PGDIR_MASK;
+ end = address + size;
+ if (end > PGDIR_SIZE)
+ end = PGDIR_SIZE;
+ phys_addr -= address;
+ if (address >= end)
+ BUG();
+ do {
+ pte_t * pte = pte_alloc(&init_mm, pmd, address);
+ if (!pte)
+ return -ENOMEM;
+ remap_area_pte(pte, address, end - address, address + phys_addr, flags);
+ address = (address + PMD_SIZE) & PMD_MASK;
+ pmd++;
+ } while (address && (address < end));
+ return 0;
+}
+
+static int remap_area_pages(unsigned long address, unsigned long phys_addr,
+ unsigned long size, unsigned long flags)
+{
+ int error;
+ pgd_t * dir;
+ unsigned long end = address + size;
+
+ phys_addr -= address;
+ dir = pgd_offset_k(address);
+ flush_cache_all();
+ if (address >= end)
+ BUG();
+ spin_lock(&init_mm.page_table_lock);
+ do {
+ pmd_t *pmd;
+ pmd = pmd_alloc(&init_mm, dir, address);
+ error = -ENOMEM;
+ if (!pmd)
+ break;
+ if (remap_area_pmd(pmd, address, end - address,
+ phys_addr + address, flags))
+ break;
+ error = 0;
+ address = (address + PGDIR_SIZE) & PGDIR_MASK;
+ dir++;
+ } while (address && (address < end));
+ spin_unlock(&init_mm.page_table_lock);
+ flush_tlb_all();
+ return error;
+}
+
+/*
+ * Generic mapping function (not visible outside):
+ */
+
+/*
+ * Remap an arbitrary physical address space into the kernel virtual
+ * address space. Needed when the kernel wants to access high addresses
+ * directly.
+ *
+ * NOTE! We need to allow non-page-aligned mappings too: we will obviously
+ * have to convert them into an offset in a page-aligned mapping, but the
+ * caller shouldn't need to know that small detail.
+ */
+void * __ia64_ioremap(unsigned long phys_addr, unsigned long size, unsigned long flags)
+{
+ void * addr;
+ struct vm_struct * area;
+ unsigned long offset, last_addr;
+
+ /* Don't allow wraparound or zero size */
+ last_addr = phys_addr + size - 1;
+ if (!size || last_addr < phys_addr)
+ return NULL;
+
+ /*
+ * Don't allow anybody to remap normal RAM that we're using..
+ */
+ if (phys_addr < virt_to_phys(high_memory))
+ return NULL;
+
+ /*
+ * Mappings have to be page-aligned
+ */
+ offset = phys_addr & ~PAGE_MASK;
+ phys_addr &= PAGE_MASK;
+ size = PAGE_ALIGN(last_addr) - phys_addr;
+
+ /*
+ * Ok, go for it..
+ */
+ area = get_vm_area(size, VM_IOREMAP);
+ if (!area)
+ return NULL;
+ addr = area->addr;
+
+ if ((flags & _PAGE_MA_MASK) == 0)
+ flags = _PAGE_MA_UC;
+
+ if (remap_area_pages(VMALLOC_VMADDR(addr), phys_addr, size, flags)) {
+ vfree(addr);
+ return NULL;
+ }
+ return (void *) (offset + (char *)addr);
+}
+
+void __ia64_iounmap(void *addr)
+{
+ return vfree(addr);
+}
--- linux-2.4.4/arch/ia64/kernel/ia64_ksyms.c.~1~ Thu Apr 5 21:51:47 2001
+++ linux-2.4.4/arch/ia64/kernel/ia64_ksyms.c Sat Aug 11 23:57:12 2001
@@ -39,6 +39,8 @@
EXPORT_SYMBOL(ip_fast_csum);

#include <asm/io.h>
+EXPORT_SYMBOL(__ia64_ioremap);
+EXPORT_SYMBOL(__ia64_iounmap);
EXPORT_SYMBOL(__ia64_memcpy_fromio);
EXPORT_SYMBOL(__ia64_memcpy_toio);
EXPORT_SYMBOL(__ia64_memset_c_io);
--- linux-2.4.4/include/asm-ia64/io.h.~1~ Thu Apr 5 21:51:47 2001
+++ linux-2.4.4/include/asm-ia64/io.h Sat Aug 11 23:59:36 2001
@@ -386,6 +386,9 @@

#define ioremap_nocache(o,s) ioremap(o,s)

+extern void * __ia64_ioremap(unsigned long offset, unsigned long size, unsigned long flags);
+extern void __ia64_iounmap(void *addr);
+
# ifdef __KERNEL__

/*