linux-kernel - Re: [PATCH v4 05/11] swiotlb: add swiotlb_set_default

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Message-Id: <20100316190805Z.fujita.tomonori@lab.ntt.co.jp>
Date:	Tue, 16 Mar 2010 19:08:46 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	albert_herranz@...oo.es
Cc:	fujita.tomonori@....ntt.co.jp, benh@...nel.crashing.org,
	linux-usb@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-ia64@...r.kernel.org, beckyb@...nel.crashing.org
Subject: Re: [PATCH v4 05/11] swiotlb: add swiotlb_set_default_size()

On Tue, 16 Mar 2010 06:58:41 +0100
Albert Herranz <albert_herranz@...oo.es> wrote:

> FUJITA Tomonori wrote:
> > On Fri, 12 Mar 2010 20:12:40 +0100
> > Albert Herranz <albert_herranz@...oo.es> wrote:
> > 
> >> The current SWIOTLB code uses a default of 64MB for the IO TLB area.
> >> This size can be influenced using a kernel command line parameter "swiotlb".
> >> Unfortunately, the parsing of the kernel command line is done _after_ the
> >> swiotlb is initialized on some architectures.
> >>
> >> This patch adds a new function swiotlb_set_default_size() which can be used
> >> before swiotlb_init() to indicate the desired IO TLB area size in bytes.
> >>
> >> This will be used later to implement a smaller IO TLB on the Nintendo Wii
> >> video game console which just comes with 24MB + 64MB of RAM.
> >>
> >> CC: linuxppc-dev@...ts.ozlabs.org
> >> CC: linux-kernel@...r.kernel.org
> >> CC: x86@...nel.org
> >> CC: linux-ia64@...r.kernel.org
> >> Signed-off-by: Albert Herranz <albert_herranz@...oo.es>
> >> ---
> >>  include/linux/swiotlb.h |    2 ++
> >>  lib/swiotlb.c           |   20 ++++++++++++++++++++
> >>  2 files changed, 22 insertions(+), 0 deletions(-)
> > 
> > Please fix the powerpc swiotlb initialization instead.
> > 
> > Calling swiotlb_init() before parsing kernel parameters sounds
> > wrong. Any reasons why you can't fix it?
> > 
> 
> I think that this would be better asked by a PowerPC maintainer. Ben?
> 
> If this is really a problem the swiotlb late init may be a solution too in this particular case.

Hmm, why swiotlb_late_init_with_default_size()?

Why can't you initialize swiotlb in mem_init() like this (only compile
tested)? Any time before freeing bootmem works for swiotlb.


diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index b152de3..8f58986 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -39,7 +39,6 @@
 #include <asm/serial.h>
 #include <asm/udbg.h>
 #include <asm/mmu_context.h>
-#include <asm/swiotlb.h>
 
 #include "setup.h"
 
@@ -343,11 +342,6 @@ void __init setup_arch(char **cmdline_p)
 		ppc_md.setup_arch();
 	if ( ppc_md.progress ) ppc_md.progress("arch: exit", 0x3eab);
 
-#ifdef CONFIG_SWIOTLB
-	if (ppc_swiotlb_enable)
-		swiotlb_init(1);
-#endif
-
 	paging_init();
 
 	/* Initialize the MMU context management stuff */
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 6354739..9143891 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -61,7 +61,6 @@
 #include <asm/xmon.h>
 #include <asm/udbg.h>
 #include <asm/kexec.h>
-#include <asm/swiotlb.h>
 #include <asm/mmu_context.h>
 
 #include "setup.h"
@@ -541,11 +540,6 @@ void __init setup_arch(char **cmdline_p)
 	if (ppc_md.setup_arch)
 		ppc_md.setup_arch();
 
-#ifdef CONFIG_SWIOTLB
-	if (ppc_swiotlb_enable)
-		swiotlb_init(1);
-#endif
-
 	paging_init();
 
 	/* Initialize the MMU context management stuff */
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 311224c..448f972 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -48,6 +48,7 @@
 #include <asm/sparsemem.h>
 #include <asm/vdso.h>
 #include <asm/fixmap.h>
+#include <asm/swiotlb.h>
 
 #include "mmu_decl.h"
 
@@ -320,6 +321,11 @@ void __init mem_init(void)
 	struct page *page;
 	unsigned long reservedpages = 0, codesize, initsize, datasize, bsssize;
 
+#ifdef CONFIG_SWIOTLB
+	if (ppc_swiotlb_enable)
+		swiotlb_init(1);
+#endif
+
 	num_physpages = lmb.memory.size >> PAGE_SHIFT;
 	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
 
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