| Message ID | 1480423205-48436-24-git-send-email-vladimir.murzin@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Nov 29, 2016 at 12:40:05PM +0000, Vladimir Murzin wrote: > With this patch applied potentially any platform can be built in NOMMU > configurations if CONFIG_EXPERT is selected. However, there is no > guaranty that platform can successfully run such Image. So the main guarantee > motivation behind of this patch: > - bring build coverage for NOMMU configurations > - allow known working NOMMU platforms (like R-class) to be used > - pave a way to add support for single address space (aka 1:1 mapping) > for MMU platforms, so they can be usable in NOMMU configurations > > Cc: Hartley Sweeten <hsweeten@visionengravers.com> > Cc: Ryan Mallon <rmallon@gmail.com> > Cc: Tony Lindgren <tony@atomide.com> > Cc: Thierry Reding <thierry.reding@gmail.com> > Cc: Alexander Shiyan <shc_work@mail.ru> > Cc: Shawn Guo <shawnguo@kernel.org> > Cc: Sascha Hauer <kernel@pengutronix.de> > Cc: Fabio Estevam <fabio.estevam@nxp.com> > Cc: Linus Walleij <linus.walleij@linaro.org> > Cc: Russell King <linux@armlinux.org.uk> > Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> > --- > arch/arm/Kconfig | 21 +++++++++++++++++++-- > 1 file changed, 19 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index e78c822..bc6f406 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -327,9 +327,9 @@ choice > > config ARCH_MULTIPLATFORM > bool "Allow multiple platforms to be selected" > - depends on MMU > + depends on MMU || EXPERT > select ARM_HAS_SG_CHAIN > - select ARM_PATCH_PHYS_VIRT > + select ARM_PATCH_PHYS_VIRT if MMU > select AUTO_ZRELADDR > select CLKSRC_OF > select COMMON_CLK > @@ -339,6 +339,23 @@ config ARCH_MULTIPLATFORM > select PCI_DOMAINS if PCI > select SPARSE_IRQ > select USE_OF > + help > + Please, read carefully if you've selected CONFIG_MMU=n! > + > + Multiplatform with !MMU configuration *is not* meant that > + kernel built to support every platform will boot on them. It > + is because physical address space layouts (particularly where > + RAM is located) are different between platforms and there is > + no MMU to work that around. > + > + You must specify where RAM start (via DRAM_BASE config > + option) and appropriate size of RAM (via DRAM_SIZE config > + option) which are valid for the platform you are building > + for. > + > + This feature is *EXPERIMENTAL*, please, consider building > + with CONFIG_MMU=y unless you know what you do or want to > + help with testing. Do you actually see this help text anywhere? I don't think multiple-choice options show help for individual choices.
On 29/11/16 17:22, Russell King - ARM Linux wrote: > On Tue, Nov 29, 2016 at 12:40:05PM +0000, Vladimir Murzin wrote: >> With this patch applied potentially any platform can be built in NOMMU >> configurations if CONFIG_EXPERT is selected. However, there is no >> guaranty that platform can successfully run such Image. So the main > > guarantee > >> motivation behind of this patch: >> - bring build coverage for NOMMU configurations >> - allow known working NOMMU platforms (like R-class) to be used >> - pave a way to add support for single address space (aka 1:1 mapping) >> for MMU platforms, so they can be usable in NOMMU configurations >> >> Cc: Hartley Sweeten <hsweeten@visionengravers.com> >> Cc: Ryan Mallon <rmallon@gmail.com> >> Cc: Tony Lindgren <tony@atomide.com> >> Cc: Thierry Reding <thierry.reding@gmail.com> >> Cc: Alexander Shiyan <shc_work@mail.ru> >> Cc: Shawn Guo <shawnguo@kernel.org> >> Cc: Sascha Hauer <kernel@pengutronix.de> >> Cc: Fabio Estevam <fabio.estevam@nxp.com> >> Cc: Linus Walleij <linus.walleij@linaro.org> >> Cc: Russell King <linux@armlinux.org.uk> >> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> >> --- >> arch/arm/Kconfig | 21 +++++++++++++++++++-- >> 1 file changed, 19 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig >> index e78c822..bc6f406 100644 >> --- a/arch/arm/Kconfig >> +++ b/arch/arm/Kconfig >> @@ -327,9 +327,9 @@ choice >> >> config ARCH_MULTIPLATFORM >> bool "Allow multiple platforms to be selected" >> - depends on MMU >> + depends on MMU || EXPERT >> select ARM_HAS_SG_CHAIN >> - select ARM_PATCH_PHYS_VIRT >> + select ARM_PATCH_PHYS_VIRT if MMU >> select AUTO_ZRELADDR >> select CLKSRC_OF >> select COMMON_CLK >> @@ -339,6 +339,23 @@ config ARCH_MULTIPLATFORM >> select PCI_DOMAINS if PCI >> select SPARSE_IRQ >> select USE_OF >> + help >> + Please, read carefully if you've selected CONFIG_MMU=n! >> + >> + Multiplatform with !MMU configuration *is not* meant that >> + kernel built to support every platform will boot on them. It >> + is because physical address space layouts (particularly where >> + RAM is located) are different between platforms and there is >> + no MMU to work that around. >> + >> + You must specify where RAM start (via DRAM_BASE config >> + option) and appropriate size of RAM (via DRAM_SIZE config >> + option) which are valid for the platform you are building >> + for. >> + >> + This feature is *EXPERIMENTAL*, please, consider building >> + with CONFIG_MMU=y unless you know what you do or want to >> + help with testing. > > Do you actually see this help text anywhere? I don't think multiple-choice > options show help for individual choices. > Yes I can: "System Type" -> "ARM system type" -> "Allow multiple platforms to be selected" -> "?". Probably not the best place, but I failed to find anything better :( Cheers Vladimir
On 11/29/2016, Vladimir Murzin wrote: > >> motivation behind of this patch: > >> - bring build coverage for NOMMU configurations > >> - allow known working NOMMU platforms (like R-class) to be used > >> - pave a way to add support for single address space (aka 1:1 mapping) > >> for MMU platforms, so they can be usable in NOMMU configurations I use XIP_KERNEL with a MMU platform (Renesas RZ/A1, Cortex A9) which is also ARCH_MULTIPLATFORM. So I also have to hack the Kconfig to get it to build. I had proposed this patch to allow you to select which multiplatform devices are XIP capable, but it never made it in. https://patchwork.kernel.org/patch/8395661/ Maybe you can do the same idea for !MMU platforms as well (just say whether the device can do XIP regardless of MMU or !MMU) Chris
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index e78c822..bc6f406 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -327,9 +327,9 @@ choice config ARCH_MULTIPLATFORM bool "Allow multiple platforms to be selected" - depends on MMU + depends on MMU || EXPERT select ARM_HAS_SG_CHAIN - select ARM_PATCH_PHYS_VIRT + select ARM_PATCH_PHYS_VIRT if MMU select AUTO_ZRELADDR select CLKSRC_OF select COMMON_CLK @@ -339,6 +339,23 @@ config ARCH_MULTIPLATFORM select PCI_DOMAINS if PCI select SPARSE_IRQ select USE_OF + help + Please, read carefully if you've selected CONFIG_MMU=n! + + Multiplatform with !MMU configuration *is not* meant that + kernel built to support every platform will boot on them. It + is because physical address space layouts (particularly where + RAM is located) are different between platforms and there is + no MMU to work that around. + + You must specify where RAM start (via DRAM_BASE config + option) and appropriate size of RAM (via DRAM_SIZE config + option) which are valid for the platform you are building + for. + + This feature is *EXPERIMENTAL*, please, consider building + with CONFIG_MMU=y unless you know what you do or want to + help with testing. config ARM_SINGLE_ARMV7M bool "ARMv7-M based platforms (Cortex-M0/M3/M4)"
With this patch applied potentially any platform can be built in NOMMU configurations if CONFIG_EXPERT is selected. However, there is no guaranty that platform can successfully run such Image. So the main motivation behind of this patch: - bring build coverage for NOMMU configurations - allow known working NOMMU platforms (like R-class) to be used - pave a way to add support for single address space (aka 1:1 mapping) for MMU platforms, so they can be usable in NOMMU configurations Cc: Hartley Sweeten <hsweeten@visionengravers.com> Cc: Ryan Mallon <rmallon@gmail.com> Cc: Tony Lindgren <tony@atomide.com> Cc: Thierry Reding <thierry.reding@gmail.com> Cc: Alexander Shiyan <shc_work@mail.ru> Cc: Shawn Guo <shawnguo@kernel.org> Cc: Sascha Hauer <kernel@pengutronix.de> Cc: Fabio Estevam <fabio.estevam@nxp.com> Cc: Linus Walleij <linus.walleij@linaro.org> Cc: Russell King <linux@armlinux.org.uk> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> --- arch/arm/Kconfig | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)