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From: Christoph Hellwig <hch@lst.de>
To: Arnd Bergmann <arnd@arndb.de>, Guo Ren <guoren@kernel.org>,
	Michal Simek <monstr@monstr.eu>,
	Greentime Hu <green.hu@gmail.com>,
	Vincent Chen <deanbo422@gmail.com>, Guan Xuetao <gxt@pku.edu.cn>,
	x86@kernel.org
Cc: linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org,
	linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
	nios2-dev@lists.rocketboards.org, openrisc@lists.librecores.org,
	linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org,
	linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
	sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
	linux-mtd@lists.infradead.org, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 10/21] asm-generic: ioremap_uc should behave the same with and without MMU
Date: Tue, 29 Oct 2019 07:48:23 +0100
Message-ID: <20191029064834.23438-11-hch@lst.de> (raw)
In-Reply-To: <20191029064834.23438-1-hch@lst.de>

Whatever reason there is for the existence of ioremap_uc, and the fact
that it returns NULL by default on architectures with an MMU applies
equally to nommu architectures, so don't provide different defaults.

In practice the difference is meaningless as the only portable driver
that uses ioremap_uc is atyfb which probably doesn't show up on nommu
devices.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/asm-generic/io.h | 36 ++++++++++++++++--------------------
 1 file changed, 16 insertions(+), 20 deletions(-)

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index d02806513670..a98ed6325727 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -935,18 +935,7 @@ static inline void *phys_to_virt(unsigned long address)
  * defined your own ioremap_*() variant you must then declare your own
  * ioremap_*() variant as defined to itself to avoid the default NULL return.
  */
-
-#ifdef CONFIG_MMU
-
-#ifndef ioremap_uc
-#define ioremap_uc ioremap_uc
-static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size)
-{
-	return NULL;
-}
-#endif
-
-#else /* !CONFIG_MMU */
+#ifndef CONFIG_MMU
 
 /*
  * Change "struct page" to physical address.
@@ -980,14 +969,6 @@ static inline void __iomem *ioremap_nocache(phys_addr_t offset, size_t size)
 }
 #endif
 
-#ifndef ioremap_uc
-#define ioremap_uc ioremap_uc
-static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size)
-{
-	return ioremap_nocache(offset, size);
-}
-#endif
-
 #ifndef ioremap_wc
 #define ioremap_wc ioremap_wc
 static inline void __iomem *ioremap_wc(phys_addr_t offset, size_t size)
@@ -1004,6 +985,21 @@ static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
 }
 #endif
 
+/*
+ * ioremap_uc is special in that we do require an explicit architecture
+ * implementation.  In general you do now want to use this function in a
+ * driver and use plain ioremap, which is uncached by default.  Similarly
+ * architectures should not implement it unless they have a very good
+ * reason.
+ */
+#ifndef ioremap_uc
+#define ioremap_uc ioremap_uc
+static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size)
+{
+	return NULL;
+}
+#endif
+
 #ifdef CONFIG_HAS_IOPORT_MAP
 #ifndef CONFIG_GENERIC_IOMAP
 #ifndef ioport_map
-- 
2.20.1


  parent reply index

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-29  6:48 generic ioremap (and lots of cleanups) v3 Christoph Hellwig
2019-10-29  6:48 ` [PATCH 01/21] arm: remove ioremap_cached Christoph Hellwig
2019-11-11 10:33   ` Arnd Bergmann
2019-10-29  6:48 ` [PATCH 02/21] unicore32: " Christoph Hellwig
2019-10-29  6:48 ` [PATCH 03/21] ia64: rename ioremap_nocache to ioremap_uc Christoph Hellwig
2019-11-11 10:36   ` Arnd Bergmann
2019-10-29  6:48 ` [PATCH 04/21] hexagon: clean up ioremap Christoph Hellwig
2019-10-29  6:48 ` [PATCH 05/21] alpha: remove the unused __ioremap wrapper Christoph Hellwig
2019-10-29  6:48 ` [PATCH 06/21] nios2: remove __ioremap Christoph Hellwig
2019-10-29  6:48 ` [PATCH 07/21] parisc: " Christoph Hellwig
2019-11-05 14:29   ` Helge Deller
2019-10-29  6:48 ` [PATCH 08/21] x86: Clean up ioremap() Christoph Hellwig
2019-10-30 10:39   ` Thomas Gleixner
2019-10-29  6:48 ` [PATCH 09/21] xtensa: clean up ioremap Christoph Hellwig
2019-10-29  6:48 ` Christoph Hellwig [this message]
2019-11-06 17:56   ` [PATCH 10/21] asm-generic: ioremap_uc should behave the same with and without MMU Palmer Dabbelt
2019-11-11 10:09   ` Arnd Bergmann
2019-11-11 10:15     ` Christoph Hellwig
2019-11-11 10:27       ` Arnd Bergmann
2019-11-11 10:29         ` Christoph Hellwig
2019-11-11 19:33           ` Arnd Bergmann
2019-10-29  6:48 ` [PATCH 11/21] asm-generic: don't provide ioremap for CONFIG_MMU Christoph Hellwig
2019-11-06 18:11   ` Palmer Dabbelt
2019-11-06 18:16     ` Geert Uytterhoeven
2019-11-06 18:28       ` Christoph Hellwig
2019-11-11 10:31       ` Arnd Bergmann
2019-11-11 10:29   ` Arnd Bergmann
2019-10-29  6:48 ` [PATCH 12/21] arch: rely on asm-generic/io.h for default ioremap_* definitions Christoph Hellwig
2019-11-07 15:29   ` Palmer Dabbelt
2019-11-11 10:10   ` Arnd Bergmann
2019-10-29  6:48 ` [PATCH 13/21] m68k: rename __iounmap and mark it static Christoph Hellwig
2019-10-30  8:51   ` Geert Uytterhoeven
2019-10-29  6:48 ` [PATCH 14/21] hexagon: remove __iounmap Christoph Hellwig
2019-10-29  6:48 ` [PATCH 15/21] nios2: " Christoph Hellwig
2019-10-29  6:48 ` [PATCH 16/21] sh: " Christoph Hellwig
2019-10-29  6:48 ` [PATCH 17/21] lib: provide a simple generic ioremap implementation Christoph Hellwig
2019-11-07 15:29   ` Palmer Dabbelt
2019-11-11 10:10   ` Arnd Bergmann
2019-10-29  6:48 ` [PATCH 18/21] riscv: use the generic ioremap code Christoph Hellwig
2019-10-29  6:48 ` [PATCH 19/21] nds32: use generic ioremap Christoph Hellwig
2019-11-12  8:51   ` Greentime Hu
2019-10-29  6:48 ` [PATCH 20/21] csky: remove ioremap_cache Christoph Hellwig
2019-10-29  6:48 ` [PATCH 21/21] csky: use generic ioremap Christoph Hellwig
2019-11-05  1:31 ` generic ioremap (and lots of cleanups) v3 Christoph Hellwig
2019-11-07 20:47 ` generic-iomap tree for linux-next Christoph Hellwig
2019-11-08  2:20   ` Stephen Rothwell
2019-11-08  4:52     ` Stephen Rothwell
2019-11-08  5:14       ` Christoph Hellwig
  -- strict thread matches above, loose matches on Subject: below --
2019-10-17 17:45 generic ioremap (and lots of cleanups) v2 Christoph Hellwig
2019-10-17 17:45 ` [PATCH 10/21] asm-generic: ioremap_uc should behave the same with and without MMU Christoph Hellwig

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