Modern MIPS cores (like P5600/6600, M5150/6520, end so on) which got L2-cache on chip also can enable a special type Cache-Coherency attribute (CCA) named UnCached Accelerated attribute (UCA). In this way uncached accelerated accesses are treated the same way as non-accelerated uncached accesses, but uncached stores are gathered together for more efficient bus utilization. So to speak this CCA enables uncached transactions to better utilize bus bandwidth via burst transactions.
This is exactly why ioremap_wc() method has been introduced in linux. Alas MIPS-platform code hasn't implemented it so far, instead default one has been used which was an alias to ioremap_nocache. In order to fix this we added MIPS-specific ioremap_wc() macro substituted by generic __ioremap_mode() method call with writecombine CPU-info field passed. It shall create real ioremap_wc() method if CPU-cache supports UCA feature and fall-back to _CACHE_UNCACHED attribute if one doesn't. Additionally platform-specific io.h shall declare ARCH_HAS_IOREMAP_WC macro as indication of architectural definition of ioremap_wc() (similar to x86/powerpc).
Signed-off-by: Serge Semin fancer.lancer@gmail.com Singed-off-by: Paul Burton paul.burton@mips.com Cc: James Hogan jhogan@kernel.org Cc: Ralf Baechle ralf@linux-mips.org Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org --- arch/mips/include/asm/io.h | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+)
diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h index 4d709b61d..d4f8cdc58 100644 --- a/arch/mips/include/asm/io.h +++ b/arch/mips/include/asm/io.h @@ -12,6 +12,8 @@ #ifndef _ASM_IO_H #define _ASM_IO_H
+#define ARCH_HAS_IOREMAP_WC + #include <linux/compiler.h> #include <linux/kernel.h> #include <linux/types.h> @@ -278,6 +280,27 @@ static inline void __iomem * __ioremap_mode(phys_addr_t offset, unsigned long si #define ioremap_cache ioremap_cachable
/* + * ioremap_wc - map bus memory into CPU space + * @offset: bus address of the memory + * @size: size of the resource to map + * + * ioremap_wc performs a platform specific sequence of operations to + * make bus memory CPU accessible via the readb/readw/readl/writeb/ + * writew/writel functions and the other mmio helpers. The returned + * address is not guaranteed to be usable directly as a virtual + * address. + * + * This version of ioremap ensures that the memory is marked uncachable + * but accelerated by means of write-combining feature. It is specifically + * useful for PCIe prefetchable windows, which may vastly improve a + * communications performance. If it was determined on boot stage, what + * CPU CCA doesn't support UCA, the method shall fall-back to the + * _CACHE_UNCACHED option (see cpu_probe() method). + */ +#define ioremap_wc(offset, size) \ + __ioremap_mode((offset), (size), boot_cpu_data.writecombine) + +/* * These two are MIPS specific ioremap variant. ioremap_cacheable_cow * requests a cachable mapping, ioremap_uncached_accelerated requests a * mapping using the uncached accelerated mode which isn't supported on
Adaptive ioremap_wc() method is now available (see "mips: mm: Create UCA-based ioremap_wc() method" commit). We can use it for UCA-featured MMIO transactions in the kernel, so we don't need it platform clone ioremap_uncached_accelerated() being declard. Seeing it is also unused anywhere in the kernel code, lets remove it from io.h arch-specific header then.
Signed-off-by: Serge Semin fancer.lancer@gmail.com Singed-off-by: Paul Burton paul.burton@mips.com Cc: James Hogan jhogan@kernel.org Cc: Ralf Baechle ralf@linux-mips.org Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org --- arch/mips/include/asm/io.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h index babe5155a..360b7ddeb 100644 --- a/arch/mips/include/asm/io.h +++ b/arch/mips/include/asm/io.h @@ -301,15 +301,11 @@ static inline void __iomem * __ioremap_mode(phys_addr_t offset, unsigned long si __ioremap_mode((offset), (size), boot_cpu_data.writecombine)
/* - * These two are MIPS specific ioremap variant. ioremap_cacheable_cow - * requests a cachable mapping, ioremap_uncached_accelerated requests a - * mapping using the uncached accelerated mode which isn't supported on - * all processors. + * This is a MIPS specific ioremap variant. ioremap_cacheable_cow + * requests a cachable mapping with CWB attribute enabled. */ #define ioremap_cacheable_cow(offset, size) \ __ioremap_mode((offset), (size), _CACHE_CACHABLE_COW) -#define ioremap_uncached_accelerated(offset, size) \ - __ioremap_mode((offset), (size), _CACHE_UNCACHED_ACCELERATED)
static inline void iounmap(const volatile void __iomem *addr) {
' On Mon, Jul 9, 2018 at 3:57 PM Serge Semin fancer.lancer@gmail.com wrote:
Adaptive ioremap_wc() method is now available (see "mips: mm: Create UCA-based ioremap_wc() method" commit). We can use it for UCA-featured MMIO transactions in the kernel, so we don't need it platform clone ioremap_uncached_accelerated() being declard. Seeing it is also unused anywhere in the kernel code, lets remove it from io.h arch-specific header then.
Signed-off-by: Serge Semin fancer.lancer@gmail.com Singed-off-by: Paul Burton paul.burton@mips.com
nit: 'Signed' (on both patches)
Cc: James Hogan jhogan@kernel.org Cc: Ralf Baechle ralf@linux-mips.org Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org
arch/mips/include/asm/io.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h index babe5155a..360b7ddeb 100644 --- a/arch/mips/include/asm/io.h +++ b/arch/mips/include/asm/io.h @@ -301,15 +301,11 @@ static inline void __iomem * __ioremap_mode(phys_addr_t offset, unsigned long si __ioremap_mode((offset), (size), boot_cpu_data.writecombine)
/*
- These two are MIPS specific ioremap variant. ioremap_cacheable_cow
- requests a cachable mapping, ioremap_uncached_accelerated requests a
- mapping using the uncached accelerated mode which isn't supported on
- all processors.
- This is a MIPS specific ioremap variant. ioremap_cacheable_cow
*/
- requests a cachable mapping with CWB attribute enabled.
#define ioremap_cacheable_cow(offset, size) \ __ioremap_mode((offset), (size), _CACHE_CACHABLE_COW) -#define ioremap_uncached_accelerated(offset, size) \
__ioremap_mode((offset), (size), _CACHE_UNCACHED_ACCELERATED)static inline void iounmap(const volatile void __iomem *addr) { -- 2.12.0
On Tue, Jul 10, 2018 at 09:15:17AM +0200, Mathieu Malaterre malat@debian.org wrote:
' On Mon, Jul 9, 2018 at 3:57 PM Serge Semin fancer.lancer@gmail.com wrote:
Adaptive ioremap_wc() method is now available (see "mips: mm: Create UCA-based ioremap_wc() method" commit). We can use it for UCA-featured MMIO transactions in the kernel, so we don't need it platform clone ioremap_uncached_accelerated() being declard. Seeing it is also unused anywhere in the kernel code, lets remove it from io.h arch-specific header then.
Signed-off-by: Serge Semin fancer.lancer@gmail.com Singed-off-by: Paul Burton paul.burton@mips.com
nit: 'Signed' (on both patches)
Good catch! Thanks. Didn't notice the typo. Should have copy-pasted both the signature and the e-mail from another letter.
I'll fix it if there will be a second version of the patchset. Otherwise I suppose it would be easier for the integrator to do this.
Regards, -Sergey
Cc: James Hogan jhogan@kernel.org Cc: Ralf Baechle ralf@linux-mips.org Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org
arch/mips/include/asm/io.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h index babe5155a..360b7ddeb 100644 --- a/arch/mips/include/asm/io.h +++ b/arch/mips/include/asm/io.h @@ -301,15 +301,11 @@ static inline void __iomem * __ioremap_mode(phys_addr_t offset, unsigned long si __ioremap_mode((offset), (size), boot_cpu_data.writecombine)
/*
- These two are MIPS specific ioremap variant. ioremap_cacheable_cow
- requests a cachable mapping, ioremap_uncached_accelerated requests a
- mapping using the uncached accelerated mode which isn't supported on
- all processors.
- This is a MIPS specific ioremap variant. ioremap_cacheable_cow
*/
- requests a cachable mapping with CWB attribute enabled.
#define ioremap_cacheable_cow(offset, size) \ __ioremap_mode((offset), (size), _CACHE_CACHABLE_COW) -#define ioremap_uncached_accelerated(offset, size) \
__ioremap_mode((offset), (size), _CACHE_UNCACHED_ACCELERATED)static inline void iounmap(const volatile void __iomem *addr) { -- 2.12.0
Hi Sergey,
On Tue, Jul 10, 2018 at 10:48:15AM +0300, Serge Semin wrote:
On Tue, Jul 10, 2018 at 09:15:17AM +0200, Mathieu Malaterre malat@debian.org wrote:
On Mon, Jul 9, 2018 at 3:57 PM Serge Semin fancer.lancer@gmail.com wrote:
Adaptive ioremap_wc() method is now available (see "mips: mm: Create UCA-based ioremap_wc() method" commit). We can use it for UCA-featured MMIO transactions in the kernel, so we don't need it platform clone ioremap_uncached_accelerated() being declard. Seeing it is also unused anywhere in the kernel code, lets remove it from io.h arch-specific header then.
Signed-off-by: Serge Semin fancer.lancer@gmail.com Singed-off-by: Paul Burton paul.burton@mips.com
nit: 'Signed' (on both patches)
Good catch! Thanks. Didn't notice the typo. Should have copy-pasted both the signature and the e-mail from another letter.
I'll fix it if there will be a second version of the patchset. Otherwise I suppose it would be easier for the integrator to do this.
I've fixed this up & applied these 2 patches with minor tweaks to mips-next for 4.19.
However FYI for next time - you shouldn't really add someone else's Signed-off-by tag anyway. The tag effectively states that a person can agree to the Developer's Certificate of Origin for this patch (see Documentation/process/submitting-patches.rst), and you can't agree that on behalf of someone else. Generally a maintainer should add this tag for themselves when they apply a patch.
Anyway, I think we should reserve the Singed-off-by tag for patches that quell fires. ;)
Thanks, Paul
On Tue, Jul 10, 2018 at 10:59:40AM -0700, Paul Burton paul.burton@mips.com wrote: Hello Paul,
Hi Sergey,
On Tue, Jul 10, 2018 at 10:48:15AM +0300, Serge Semin wrote:
On Tue, Jul 10, 2018 at 09:15:17AM +0200, Mathieu Malaterre malat@debian.org wrote:
On Mon, Jul 9, 2018 at 3:57 PM Serge Semin fancer.lancer@gmail.com wrote:
Adaptive ioremap_wc() method is now available (see "mips: mm: Create UCA-based ioremap_wc() method" commit). We can use it for UCA-featured MMIO transactions in the kernel, so we don't need it platform clone ioremap_uncached_accelerated() being declard. Seeing it is also unused anywhere in the kernel code, lets remove it from io.h arch-specific header then.
Signed-off-by: Serge Semin fancer.lancer@gmail.com Singed-off-by: Paul Burton paul.burton@mips.com
nit: 'Signed' (on both patches)
Good catch! Thanks. Didn't notice the typo. Should have copy-pasted both the signature and the e-mail from another letter.
I'll fix it if there will be a second version of the patchset. Otherwise I suppose it would be easier for the integrator to do this.
I've fixed this up & applied these 2 patches with minor tweaks to mips-next for 4.19.
Great! Thanks.
However FYI for next time - you shouldn't really add someone else's Signed-off-by tag anyway. The tag effectively states that a person can agree to the Developer's Certificate of Origin for this patch (see Documentation/process/submitting-patches.rst), and you can't agree that on behalf of someone else. Generally a maintainer should add this tag for themselves when they apply a patch.
I'm sorry if it seemed like I added Signed-off on your behalf. I thought the Signed-off also concerns the ones, who participated in the patch preparation. Since you suggested the design of the change, I've decided to put your name in the Signed-off tag. What shall I use in this way then?
Anyway, I think we should reserve the Singed-off-by tag for patches that quell fires. ;)
Thanks, Paul
Regards, -Sergey
Hi Serge,
On Tue, Jul 10, 2018 at 10:13:54PM +0300, Serge Semin wrote:
On Tue, Jul 10, 2018 at 10:59:40AM -0700, Paul Burton paul.burton@mips.com wrote:
However FYI for next time - you shouldn't really add someone else's Signed-off-by tag anyway. The tag effectively states that a person can agree to the Developer's Certificate of Origin for this patch (see Documentation/process/submitting-patches.rst), and you can't agree that on behalf of someone else. Generally a maintainer should add this tag for themselves when they apply a patch.
I'm sorry if it seemed like I added Signed-off on your behalf.
That's OK, I didn't think you did it maliciously :)
I thought the Signed-off also concerns the ones, who participated in the patch preparation. Since you suggested the design of the change, I've decided to put your name in the Signed-off tag. What shall I use in this way then?
In this case Suggested-by might have been a good choice. Reported-by is also commonly used if someone reported a problem which you created a fix for.
Section 13 of Documentation/process/submitting-patches.rst describes these tags along with a couple others.
Thanks, Paul
Paul,
On Tue, Jul 10, 2018 at 02:04:15PM -0700, Paul Burton paul.burton@mips.com wrote:
Hi Serge,
On Tue, Jul 10, 2018 at 10:13:54PM +0300, Serge Semin wrote:
On Tue, Jul 10, 2018 at 10:59:40AM -0700, Paul Burton paul.burton@mips.com wrote:
However FYI for next time - you shouldn't really add someone else's Signed-off-by tag anyway. The tag effectively states that a person can agree to the Developer's Certificate of Origin for this patch (see Documentation/process/submitting-patches.rst), and you can't agree that on behalf of someone else. Generally a maintainer should add this tag for themselves when they apply a patch.
I'm sorry if it seemed like I added Signed-off on your behalf.
That's OK, I didn't think you did it maliciously :)
I thought the Signed-off also concerns the ones, who participated in the patch preparation. Since you suggested the design of the change, I've decided to put your name in the Signed-off tag. What shall I use in this way then?
In this case Suggested-by might have been a good choice. Reported-by is also commonly used if someone reported a problem which you created a fix for.
Section 13 of Documentation/process/submitting-patches.rst describes these tags along with a couple others.
I always thought of these tags as something more like a formality. In fact this hasn't been my first patchset sent to the kernel e-mailing list. Although all of the previous ones didn't involve someone else participating in the changes development, except the reviewers of course. So I do aware of all the tags mentioned in the doc. But as it turns out I didn't fully understand their meaning. Main rule: most of the tags should not be added without the permission, except more or less formal CC and Fixes ones. Anyway thanks for the advice. Next time I'll be more careful with it.
Regards, -Sergey
Thanks, Paul
- This is a MIPS specific ioremap variant. ioremap_cacheable_cow
*/
- requests a cachable mapping with CWB attribute enabled.
#define ioremap_cacheable_cow(offset, size) \ __ioremap_mode((offset), (size), _CACHE_CACHABLE_COW)
This isn't actually used anywhere in the kernel tree. Please remove it as well.
Hello Christoph,
On Tue, Jul 10, 2018 at 11:56:31PM -0700, Christoph Hellwig hch@infradead.org wrote:
- This is a MIPS specific ioremap variant. ioremap_cacheable_cow
*/
- requests a cachable mapping with CWB attribute enabled.
#define ioremap_cacheable_cow(offset, size) \ __ioremap_mode((offset), (size), _CACHE_CACHABLE_COW)
This isn't actually used anywhere in the kernel tree. Please remove it as well.
I don't really know whether it is necessary at this point. We discarded the ioremap_uncached_accelerated() method, since the obvious alternative is now available: ioremap_wc(). While ioremap_cacheable_cow() hasn't got one. So if it was up to me, I'd leave it here. Anyway if the subsystem maintainers think otherwise, I won't refuse to submit a patch with this method removal.
Regards, -Sergey
On Wed, Jul 11, 2018 at 04:52:10PM +0300, Serge Semin wrote:
Hello Christoph,
On Tue, Jul 10, 2018 at 11:56:31PM -0700, Christoph Hellwig hch@infradead.org wrote:
- This is a MIPS specific ioremap variant. ioremap_cacheable_cow
*/
- requests a cachable mapping with CWB attribute enabled.
#define ioremap_cacheable_cow(offset, size) \ __ioremap_mode((offset), (size), _CACHE_CACHABLE_COW)
This isn't actually used anywhere in the kernel tree. Please remove it as well.
I don't really know whether it is necessary at this point. We discarded the ioremap_uncached_accelerated() method, since the obvious alternative is now available: ioremap_wc(). While ioremap_cacheable_cow() hasn't got one. So if it was up to me, I'd leave it here. Anyway if the subsystem maintainers think otherwise, I won't refuse to submit a patch with this method removal.
The function is entirely unused in the kernel tree, please remove it.
linux-stable-mirror@lists.linaro.org
-
Christoph Hellwig -
Mathieu Malaterre -
Paul Burton -
Serge Semin