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* [PATCH] openrisc: Implement fixmap to fix eralycon
@ 2024-09-27 14:56 Stafford Horne
  2024-09-27 18:13 ` Stafford Horne
  0 siblings, 1 reply; 2+ messages in thread
From: Stafford Horne @ 2024-09-27 14:56 UTC (permalink / raw)
  To: LKML
  Cc: Stafford Horne, Jonas Bonn, Stefan Kristiansson, Dawei Li,
	Baoquan He, Andrew Morton, Mike Rapoport (IBM), linux-openrisc

With commit 53c98e35dcbc ("openrisc: mm: remove unneeded early ioremap
code") it was commented that early ioremap was not used in OpenRISC.  I
acked this but was wrong.  Earlycon now fails with the below trace:

    Kernel command line: earlycon
    ------------[ cut here ]------------
    WARNING: CPU: 0 PID: 0 at mm/ioremap.c:23
    generic_ioremap_prot+0x118/0x130
    Modules linked in:
    CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted
    6.11.0-rc5-00001-gce02fd891c38-dirty #141
    Call trace:
    [<(ptrval)>] dump_stack_lvl+0x7c/0x9c
    [<(ptrval)>] dump_stack+0x1c/0x2c
    [<(ptrval)>] __warn+0xb4/0x108
    [<(ptrval)>] ? generic_ioremap_prot+0x118/0x130
    [<(ptrval)>] warn_slowpath_fmt+0x60/0x98
    [<(ptrval)>] generic_ioremap_prot+0x118/0x130
    [<(ptrval)>] ioremap_prot+0x20/0x30
    [<(ptrval)>] of_setup_earlycon+0xd4/0x2e0
    [<(ptrval)>] early_init_dt_scan_chosen_stdout+0x18c/0x1c8
    [<(ptrval)>] param_setup_earlycon+0x3c/0x60
    [<(ptrval)>] do_early_param+0xb0/0x118
    [<(ptrval)>] parse_args+0x184/0x4b8
    [<(ptrval)>] ? start_kernel+0x0/0x78c
    [<(ptrval)>] parse_early_options+0x40/0x50
    [<(ptrval)>] ? do_early_param+0x0/0x118
    [<(ptrval)>] parse_early_param+0x48/0x68
    [<(ptrval)>] ? start_kernel+0x318/0x78c
    [<(ptrval)>] ? start_kernel+0x0/0x78c
    ---[ end trace 0000000000000000 ]---

To fix this we could either implement early_ioremap or implement fixmap.
In this patch we choose the later option of implementing basic fixmap
support.

While fixing this we also remove the old FIX_IOREMAP slots that were
used by early ioremap code.  That code was also removed by commit
53c98e35dcbc ("openrisc: mm: remove unneeded early ioremap code") but
these definitions were not cleaned up.

Fixes: 53c98e35dcbc ("openrisc: mm: remove unneeded early ioremap code")
Signed-off-by: Stafford Horne <shorne@gmail.com>
---
 arch/openrisc/Kconfig              |  3 +++
 arch/openrisc/include/asm/fixmap.h | 21 +++++-------------
 arch/openrisc/mm/init.c            | 34 ++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index 69c0258700b2..3279ef457c57 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -65,6 +65,9 @@ config STACKTRACE_SUPPORT
 config LOCKDEP_SUPPORT
 	def_bool  y
 
+config FIX_EARLYCON_MEM
+	def_bool y
+
 menu "Processor type and features"
 
 choice
diff --git a/arch/openrisc/include/asm/fixmap.h b/arch/openrisc/include/asm/fixmap.h
index ecdb98a5839f..aaa6a26a3e92 100644
--- a/arch/openrisc/include/asm/fixmap.h
+++ b/arch/openrisc/include/asm/fixmap.h
@@ -26,29 +26,18 @@
 #include <linux/bug.h>
 #include <asm/page.h>
 
-/*
- * On OpenRISC we use these special fixed_addresses for doing ioremap
- * early in the boot process before memory initialization is complete.
- * This is used, in particular, by the early serial console code.
- *
- * It's not really 'fixmap', per se, but fits loosely into the same
- * paradigm.
- */
 enum fixed_addresses {
-	/*
-	 * FIX_IOREMAP entries are useful for mapping physical address
-	 * space before ioremap() is useable, e.g. really early in boot
-	 * before kmalloc() is working.
-	 */
-#define FIX_N_IOREMAPS  32
-	FIX_IOREMAP_BEGIN,
-	FIX_IOREMAP_END = FIX_IOREMAP_BEGIN + FIX_N_IOREMAPS - 1,
+	FIX_EARLYCON_MEM_BASE,
 	__end_of_fixed_addresses
 };
 
 #define FIXADDR_SIZE		(__end_of_fixed_addresses << PAGE_SHIFT)
 /* FIXADDR_BOTTOM might be a better name here... */
 #define FIXADDR_START		(FIXADDR_TOP - FIXADDR_SIZE)
+#define FIXMAP_PAGE_IO		PAGE_KERNEL_NOCACHE
+
+extern void __set_fixmap(enum fixed_addresses idx,
+			 phys_addr_t phys, pgprot_t flags);
 
 #include <asm-generic/fixmap.h>
 
diff --git a/arch/openrisc/mm/init.c b/arch/openrisc/mm/init.c
index 1dcd78c8f0e9..7397d18c95d7 100644
--- a/arch/openrisc/mm/init.c
+++ b/arch/openrisc/mm/init.c
@@ -207,6 +207,40 @@ void __init mem_init(void)
 	return;
 }
 
+static int __init map_page(unsigned long va, phys_addr_t pa, int flags)
+{
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pd;
+	pte_t *pg;
+	int err = -ENOMEM;
+
+	p4d = p4d_offset(pgd_offset_k(va), va);
+	pud = pud_offset(p4d, va);
+	pd = pmd_offset(pud, va);
+	pg = pte_alloc_kernel(pd, va);
+
+	if (pg != NULL) {
+		err = 0;
+		set_pte_at(&init_mm, va, pg, pfn_pte(pa >> PAGE_SHIFT,
+				__pgprot(flags)));
+	}
+	return err;
+}
+
+void __init __set_fixmap(enum fixed_addresses idx,
+			 phys_addr_t phys, pgprot_t prot)
+{
+	unsigned long address = __fix_to_virt(idx);
+
+	if (idx >= __end_of_fixed_addresses) {
+		BUG();
+		return;
+	}
+
+	map_page(address, phys, pgprot_val(prot));
+}
+
 static const pgprot_t protection_map[16] = {
 	[VM_NONE]					= PAGE_NONE,
 	[VM_READ]					= PAGE_READONLY_X,
-- 
2.44.0


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2024-09-27 14:56 [PATCH] openrisc: Implement fixmap to fix eralycon Stafford Horne
2024-09-27 18:13 ` Stafford Horne

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