Re: [PATCH v1 3/4] powerpc: Add support for GENERIC_EARLY_IOREMAP

Le 12/09/2019 à 17:50, Aneesh Kumar K.V a écrit :

Christophe Leroy [off-list ref] writes:

quoted

Le 12/09/2019 à 17:37, Aneesh Kumar K.V a écrit :

quoted

Christophe Leroy [off-list ref] writes:

quoted

Add support for GENERIC_EARLY_IOREMAP.

Let's define 16 slots of 256Kbytes each for early ioremap.

Signed-off-by: Christophe Leroy <redacted>
---
   arch/powerpc/Kconfig              |  1 +
   arch/powerpc/include/asm/Kbuild   |  1 +
   arch/powerpc/include/asm/fixmap.h | 12 ++++++++++++
   arch/powerpc/kernel/setup_32.c    |  3 +++
   arch/powerpc/kernel/setup_64.c    |  3 +++
   5 files changed, 20 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 6a7c797fa9d2..8fe252962518 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -161,6 +161,7 @@ config PPC
   	select GENERIC_CMOS_UPDATE
   	select GENERIC_CPU_AUTOPROBE
   	select GENERIC_CPU_VULNERABILITIES	if PPC_BARRIER_NOSPEC
+	select GENERIC_EARLY_IOREMAP
   	select GENERIC_IRQ_SHOW
   	select GENERIC_IRQ_SHOW_LEVEL
   	select GENERIC_PCI_IOMAP		if PCI

diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild
index 9a1d2fc6ceb7..30829120659c 100644
--- a/arch/powerpc/include/asm/Kbuild
+++ b/arch/powerpc/include/asm/Kbuild

@@ -12,3 +12,4 @@ generic-y += preempt.h
   generic-y += vtime.h
   generic-y += msi.h
   generic-y += simd.h
+generic-y += early_ioremap.h

diff --git a/arch/powerpc/include/asm/fixmap.h b/arch/powerpc/include/asm/fixmap.h
index 722289a1d000..d5c4d357bd33 100644
--- a/arch/powerpc/include/asm/fixmap.h
+++ b/arch/powerpc/include/asm/fixmap.h

@@ -15,6 +15,7 @@
   #define _ASM_FIXMAP_H
   
   #ifndef __ASSEMBLY__
+#include <linux/sizes.h>
   #include <asm/page.h>
   #include <asm/pgtable.h>
   #ifdef CONFIG_HIGHMEM

@@ -64,6 +65,14 @@ enum fixed_addresses {
   		       FIX_IMMR_SIZE,
   #endif
   	/* FIX_PCIE_MCFG, */
+	__end_of_permanent_fixed_addresses,
+
+#define NR_FIX_BTMAPS		(SZ_256K / PAGE_SIZE)
+#define FIX_BTMAPS_SLOTS	16
+#define TOTAL_FIX_BTMAPS	(NR_FIX_BTMAPS * FIX_BTMAPS_SLOTS)
+
+	FIX_BTMAP_END = __end_of_permanent_fixed_addresses,
+	FIX_BTMAP_BEGIN = FIX_BTMAP_END + TOTAL_FIX_BTMAPS - 1,
   	__end_of_fixed_addresses
   };
   

@@ -71,6 +80,7 @@ enum fixed_addresses {
   #define FIXADDR_START		(FIXADDR_TOP - __FIXADDR_SIZE)
   
   #define FIXMAP_PAGE_NOCACHE PAGE_KERNEL_NCG
+#define FIXMAP_PAGE_IO	PAGE_KERNEL_NCG
   
   #include <asm-generic/fixmap.h>
   

@@ -85,5 +95,7 @@ static inline void __set_fixmap(enum fixed_addresses idx,
   	map_kernel_page(__fix_to_virt(idx), phys, flags);
   }
   
+#define __early_set_fixmap	__set_fixmap
+
   #endif /* !__ASSEMBLY__ */
   #endif

diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index a7541edf0cdb..dcffe927f5b9 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c

@@ -44,6 +44,7 @@
   #include <asm/asm-prototypes.h>
   #include <asm/kdump.h>
   #include <asm/feature-fixups.h>
+#include <asm/early_ioremap.h>
   
   #include "setup.h"
   

@@ -80,6 +81,8 @@ notrace void __init machine_init(u64 dt_ptr)
   	/* Configure static keys first, now that we're relocated. */
   	setup_feature_keys();
   
+	early_ioremap_setup();
+
   	/* Enable early debugging if any specified (see udbg.h) */
   	udbg_early_init();
   

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 44b4c432a273..b85f6a1cc3a1 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c

@@ -65,6 +65,7 @@
   #include <asm/hw_irq.h>
   #include <asm/feature-fixups.h>
   #include <asm/kup.h>
+#include <asm/early_ioremap.h>
   
   #include "setup.h"
   

@@ -338,6 +339,8 @@ void __init early_setup(unsigned long dt_ptr)
   	apply_feature_fixups();
   	setup_feature_keys();
   
+	early_ioremap_setup();
+
   	/* Initialize the hash table or TLB handling */
   	early_init_mmu();
   

Can we remove early_ioremap_range() after this?

Yes, once all early callers of ioremap functions are converted to using
early_ioremap()

Why can't we switch the early callers to early_ioremap and print a
warning?

ie,
if (!slab_available()) {
    pr_warn("switch to early_ioremap");
    early_ioremap();
}

Because:
- early_iounmap() requires the size of the area to be freed unlike iounmap()
- early_ioremap() is for ephemeral mappings. All early mapping must be 
gone at the end of init (this is verified by 
late_initcall(check_early_ioremap_leak))

Second point means another approach has to be taken for installing early 
permanent mapping, for instance by using fixmaps.

Christophe