linux-kernel - [PATCH v2 01/16] resource: Add System RAM resource type

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Message-Id: <1451081365-15190-1-git-send-email-toshi.kani@hpe.com>
Date:	Fri, 25 Dec 2015 15:09:10 -0700
From:	Toshi Kani <toshi.kani@....com>
To:	akpm@...ux-foundation.org, bp@...en8.de
Cc:	linux-arch@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Toshi Kani <toshi.kani@....com>
Subject: [PATCH v2 01/16] resource: Add System RAM resource type

I/O resource type, IORESOURCE_MEM, is used for all types of
memory-mapped ranges, ex. System RAM, System ROM, Video RAM,
Persistent Memory, PCI Bus, PCI MMCONFIG, ACPI Tables, IOAPIC,
reserved, and so on.  This requires walk_system_ram_range(),
walk_system_ram_res(), and region_intersects() to use strcmp()
against string "System RAM" to search for System RAM ranges in
the iomem table, which is inefficient.  __ioremap_caller() and
reserve_memtype() on x86, for instance, call walk_system_ram_range()
for every request to check if a given range is in System RAM ranges.

However, adding a new I/O resource type for System RAM is not
a viable option [1].  There are approx. 3800 references to
IORESOURCE_MEM in the kernel/drivers, which make it very
difficult to distinguish their usages between new type and
IORESOURCE_MEM.  The I/O resource types are also used by the
PNP subsystem.  Therefore, this patch introduces an extended
I/O resource type, IORESOURCE_SYSTEM_RAM, which consists of
IORESOURCE_MEM and a new modifier flag IORESOURCE_SYSRAM [2].

To keep the code 'if (resource_type(r) == IORESOURCE_MEM)' to
work continuously for System RAM, resource_ext_type() is added
for extracting extended type bit(s).

Link[1]: http://lkml.kernel.org/r/<1449168859.9855.54.camel@....com>
Link[2]: http://lkml.kernel.org/r/<CA+55aFy4WQrWexC4u2LxX9Mw2NVoznw7p3Yh=iF4Xtf7zKWnRw@...l.gmail.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Toshi Kani <toshi.kani@....com>
---
 include/linux/ioport.h |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 24bea08..4b65d94 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -49,12 +49,19 @@ struct resource {
 #define IORESOURCE_WINDOW	0x00200000	/* forwarded by bridge */
 #define IORESOURCE_MUXED	0x00400000	/* Resource is software muxed */

+#define IORESOURCE_EXT_TYPE_BITS 0x01000000	/* Resource extended types */
+#define IORESOURCE_SYSRAM	0x01000000	/* System RAM (modifier) */
+
 #define IORESOURCE_EXCLUSIVE	0x08000000	/* Userland may not map this resource */
+
 #define IORESOURCE_DISABLED	0x10000000
 #define IORESOURCE_UNSET	0x20000000	/* No address assigned yet */
 #define IORESOURCE_AUTO		0x40000000
 #define IORESOURCE_BUSY		0x80000000	/* Driver has marked this resource busy */

+/* I/O resource extended types */
+#define IORESOURCE_SYSTEM_RAM		(IORESOURCE_MEM|IORESOURCE_SYSRAM)
+
 /* PnP IRQ specific bits (IORESOURCE_BITS) */
 #define IORESOURCE_IRQ_HIGHEDGE		(1<<0)
 #define IORESOURCE_IRQ_LOWEDGE		(1<<1)
@@ -170,6 +177,10 @@ static inline unsigned long resource_type(const struct resource *res)
 {
 	return res->flags & IORESOURCE_TYPE_BITS;
 }
+static inline unsigned long resource_ext_type(const struct resource *res)
+{
+	return res->flags & IORESOURCE_EXT_TYPE_BITS;
+}
 /* True iff r1 completely contains r2 */
 static inline bool resource_contains(struct resource *r1, struct resource *r2)
 {
--
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