arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
PATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI.
This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter.
--- arch/arm64/Kconfig | 13 +++++++++++++ arch/arm64/kernel/acpi.c | 3 ++- 2 files changed, 15 insertions(+), 1 deletion(-)
arch/arm64/Kconfig +13 -0
@@ -918,6 +918,19 @@ config DMI However, even with this option, the resultant kernel should continue to boot on existing non-UEFI platforms. +config PREFER_ACPI_OVER_DT + bool "Prefer booting via ACPI if both ACPI and DT are available" + depends on ACPI + help + If both ACPI and DT platform descriptions are available, and the + kernel was configured at build time to support both flavours, the + default policy in absence of a acpi=[off|force] kernel command line + parameter is to prefer DT over ACPI. + + This option inverts that default policy, by preferring ACPI over DT + instead. Note that this default policy is still superseded by the + value of the acpi= command line parameter. + endmenu menu "Userspace binary formats"
arch/arm64/kernel/acpi.c +2 -1
@@ -188,7 +188,8 @@ void __init acpi_boot_table_init(void)* and ACPI has not been force enabled (acpi=force) */ if (param_acpi_off || - (!param_acpi_force &&of_scan_flat_dt (dt_scan_depth1_nodes,NULL ))) + (!IS_ENABLED (CONFIG_PREFER_ACPI_OVER_DT ) && + !param_acpi_force &&of_scan_flat_dt (dt_scan_depth1_nodes,NULL )))return ;/*
Signature · 1 line
2.5.0
PATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
Quoted 9 lines · Ard Biesheuvel
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI.
This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter.
Looks sane to me
G
Quoted 47 lines
Signed-off-by Ard Biesheuvel <[email protected]>--- arch/arm64/Kconfig | 13 +++++++++++++ arch/arm64/kernel/acpi.c | 3 ++- 2 files changed, 15 insertions(+), 1 deletion(-)arch/arm64/Kconfig +13
-0@@ -918,6 +918,19 @@ config DMI However, even with this option, the resultant kernel should continue to boot on existing non-UEFI platforms. +config PREFER_ACPI_OVER_DT + bool "Prefer booting via ACPI if both ACPI and DT are available" + depends on ACPI + help + If both ACPI and DT platform descriptions are available, and the + kernel was configured at build time to support both flavours, the + default policy in absence of a acpi=[off|force] kernel command line + parameter is to prefer DT over ACPI. + + This option inverts that default policy, by preferring ACPI over DT + instead. Note that this default policy is still superseded by the + value of the acpi= command line parameter. + endmenu menu "Userspace binary formats"arch/arm64/kernel/acpi.c +2
-1@@ -188,7 +188,8 @@ void __init acpi_boot_table_init(void)* and ACPI has not been force enabled (acpi=force) */ if (param_acpi_off || - (!param_acpi_force &&of_scan_flat_dt (dt_scan_depth1_nodes,NULL ))) + (!IS_ENABLED (CONFIG_PREFER_ACPI_OVER_DT ) && + !param_acpi_force &&of_scan_flat_dt (dt_scan_depth1_nodes,NULL )))return ;/* Signature · 1 line
2.5.0
PATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
Quoted 11 lines · Graeme Gregory
Quoted 9 lines · Ard Biesheuvel
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI.
This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter.
Quoted 6 lines
Looks sane to me
Reviewed-by Graeme Gregory <[email protected]>G
Quoted 52 lines
Quoted 45 lines
Signed-off-by Ard Biesheuvel <[email protected]>--- arch/arm64/Kconfig | 13 +++++++++++++ arch/arm64/kernel/acpi.c | 3 ++- 2 files changed, 15 insertions(+), 1 deletion(-)arch/arm64/Kconfig +13
-0@@ -918,6 +918,19 @@ config DMI However, even with this option, the resultant kernel should continue to boot on existing non-UEFI platforms. +config PREFER_ACPI_OVER_DT + bool "Prefer booting via ACPI if both ACPI and DT are available" + depends on ACPI + help + If both ACPI and DT platform descriptions are available, and the + kernel was configured at build time to support both flavours, the + default policy in absence of a acpi=[off|force] kernel command line + parameter is to prefer DT over ACPI. + + This option inverts that default policy, by preferring ACPI over DT + instead. Note that this default policy is still superseded by the + value of the acpi= command line parameter. + endmenu menu "Userspace binary formats"arch/arm64/kernel/acpi.c +2
-2@@ -188,7 +188,8 @@ void __init acpi_boot_table_init(void)* and ACPI has not been force enabled (acpi=force) */ if (param_acpi_off || - (!param_acpi_force &&of_scan_flat_dt (dt_scan_depth1_nodes,NULL ))) + (!IS_ENABLED (CONFIG_PREFER_ACPI_OVER_DT ) && + !param_acpi_force &&of_scan_flat_dt (dt_scan_depth1_nodes,NULL )))return ;/* -- Quoted 2 lines
2.5.0
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Catalin Marinas
maintainerPATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
In reply to Ard BiesheuvelQuoted 8 lines · Ard Biesheuvel
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI.
This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter.
Why do we need another method to specify an ACPI boot? I thought those vendors going for ACPI wouldn't be bothered with DT anyway.
I'm not keen on having kernel builds with different behavior in respect of whether ACPI or DT is preferred.
Signature · 1 line
Catalin
PATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
Quoted 10 lines · Catalin Marinas
Quoted 8 lines · Ard Biesheuvel
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI.
This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter.
Quoted 6 lines
Why do we need another method to specify an ACPI boot? I thought those vendors going for ACPI wouldn't be bothered with DT anyway.
I'm not keen on having kernel builds with different behavior in respect of whether ACPI or DT is preferred.
How about adding support for acpi=on then? Currently, we only have acpi=off or acpi=force, and there is no way (i.e., for a distro installer) to boot via ACPI if it can but fall back to DT otherwise. Some enterprise features (like RAS) depend on ACPI boot so it may simply preferred but not mandated in some cases.
Catalin Marinas
maintainerPATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
Quoted 14 lines · Ard Biesheuvel
Quoted 13 lines · Catalin Marinas
Quoted 8 lines · Ard Biesheuvel
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI.
This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter.
Why do we need another method to specify an ACPI boot? I thought those vendors going for ACPI wouldn't be bothered with DT anyway.
Quoted 8 lines
Quoted 2 lines
I'm not keen on having kernel builds with different behavior in respect of whether ACPI or DT is preferred.
How about adding support for acpi=on then? Currently, we only have acpi=off or acpi=force, and there is no way (i.e., for a distro installer) to boot via ACPI if it can but fall back to DT otherwise. Some enterprise features (like RAS) depend on ACPI boot so it may simply preferred but not mandated in some cases.
Since this is a distro preference, I would rather have an acpi=on option.
Signature · 1 line
Catalin
PATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
Quoted 18 lines · Catalin Marinas
Quoted 17 lines · Ard Biesheuvel
Quoted 15 lines · Catalin Marinas
Quoted 8 lines · Ard Biesheuvel
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI.
This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter.
Why do we need another method to specify an ACPI boot? I thought those vendors going for ACPI wouldn't be bothered with DT anyway.
I'm not keen on having kernel builds with different behavior in respect of whether ACPI or DT is preferred.
Quoted 8 lines
Quoted 5 lines
How about adding support for acpi=on then? Currently, we only have acpi=off or acpi=force, and there is no way (i.e., for a distro installer) to boot via ACPI if it can but fall back to DT otherwise. Some enterprise features (like RAS) depend on ACPI boot so it may simply preferred but not mandated in some cases.
Since this is a distro preference, I would rather have an acpi=on option.
While this is a 'distro preference', I think it is somewhat ugly for this to be configured on
the commandline. We (HPE) don't support DT, and I don't think that
is likely to change.
While we control the firmware for our main internal platform, and don't provide a DT there,
we also do development and testing on other platforms where the firmware may provide a DT,
but we never want to use it. This requires developers/users to specify "acpi=force" on the
command-line to boot in a supported manner.
I would much rather be able to configure the kernel to prefer (or even unconditionally require)
ACPI to boot, as this will be the normal, default, and only supported way to boot for our platform,
and I expect this to also be the case in much of the enterprise space.
Since I don't think it is possible to build an arm64 kernel with only ACPI, and no DT support,
I think a kconfig option to select the preferred HW description to be used is the better solution.
Roy
Quoted 8 lines
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Catalin Marinas
maintainerPATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
Quoted 29 lines · Roy Franz (HPE)
Quoted 18 lines · Catalin Marinas
Quoted 17 lines · Ard Biesheuvel
Quoted 15 lines · Catalin Marinas
Quoted 8 lines · Ard Biesheuvel
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI.
This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter.
Why do we need another method to specify an ACPI boot? I thought those vendors going for ACPI wouldn't be bothered with DT anyway.
I'm not keen on having kernel builds with different behavior in respect of whether ACPI or DT is preferred.
Quoted 8 lines
Quoted 5 lines
How about adding support for acpi=on then? Currently, we only have acpi=off or acpi=force, and there is no way (i.e., for a distro installer) to boot via ACPI if it can but fall back to DT otherwise. Some enterprise features (like RAS) depend on ACPI boot so it may simply preferred but not mandated in some cases.
Since this is a distro preference, I would rather have an acpi=on option.
Quoted 8 lines
While this is a 'distro preference', I think it is somewhat ugly for
this to be configured on the commandline. We (HPE) don't support DT,
and I don't think that is likely to change. While we control the firmware for our main internal platform, and don't provide a DT there, we also do development and testing on other platforms where the firmware may provide a DT, but we never want to use it. This requires developers/users to specify "acpi=force" on the command-line to boot in a supported manner.
You wrongly assume that everyone wants ACPI by generalising "we" (HPE) to "developers/users".
In an ideal world where both ACPI and DT (if provided by firmware) are equally supported, such option wouldn't be much of an issue. But we are not there yet with some platforms having ACPI in an experimental state or relying on distro-only kernel patches. This means that a _mainline_ kernel configured with such ACPI default on option would require an explicit acpi=off on the command line to boot with DT. Since you don't always know which kernel you'd run, you pretty much end up with an acpi= option on the command line permanently.
Maybe those vendors providing both ACPI and DT have a good reason like ACPI support not ready.
Quoted 4 lines
I would much rather be able to configure the kernel to prefer (or even unconditionally require) ACPI to boot, as this will be the normal, default, and only supported way to boot for our platform, and I expect this to also be the case in much of the enterprise space.
I really don't care about which platform recommends ACPI or DT. What I care about is not having to enable certain config option depending on which platform you target as this leads to config fragmentation (think of single Image). I much prefer a clear kernel policy on whether ACPI or DT is used if both are provided by firmware and we've already made that call - DT takes precedence.
Quoted 3 lines
Since I don't think it is possible to build an arm64 kernel with only ACPI, and no DT support, I think a kconfig option to select the preferred HW description to be used is the better solution.
The (multi-platform, single Image) kernel is not in a position to assess whether ACPI or DT is in a better state for a given SoC. We should leave this "ACPI preferred" choice to the code running before the kernel by simply providing only ACPI tables.
Signature · 1 line
Catalin
PATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
Quoted 39 lines · Catalin Marinas
Quoted 29 lines · Roy Franz (HPE)
Quoted 18 lines · Catalin Marinas
Quoted 17 lines · Ard Biesheuvel
Quoted 15 lines · Catalin Marinas
Quoted 8 lines · Ard Biesheuvel
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI.
This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter.
Why do we need another method to specify an ACPI boot? I thought those vendors going for ACPI wouldn't be bothered with DT anyway.
I'm not keen on having kernel builds with different behavior in respect of whether ACPI or DT is preferred.
Quoted 8 lines
Quoted 5 lines
How about adding support for acpi=on then? Currently, we only have acpi=off or acpi=force, and there is no way (i.e., for a distro installer) to boot via ACPI if it can but fall back to DT otherwise. Some enterprise features (like RAS) depend on ACPI boot so it may simply preferred but not mandated in some cases.
Since this is a distro preference, I would rather have an acpi=on option.
Quoted 8 lines
While this is a 'distro preference', I think it is somewhat ugly for
this to be configured on the commandline. We (HPE) don't support DT,
and I don't think that is likely to change. While we control the firmware for our main internal platform, and don't provide a DT there, we also do development and testing on other platforms where the firmware may provide a DT, but we never want to use it. This requires developers/users to specify "acpi=force" on the command-line to boot in a supported manner.
Quoted 2 lines
You wrongly assume that everyone wants ACPI by generalising "we" (HPE) to "developers/users".
This is not what I am assuming or thinking. I think that a large enough set of arm64 developers and users care primarily/only about ACPI, and would benefit from not having to have an "acpi=xx" on the command-line forevermore. The 'we' I used, referring to HPE, is in that set.
Quoted 33 lines
In an ideal world where both ACPI and DT (if provided by firmware) are equally supported, such option wouldn't be much of an issue. But we are not there yet with some platforms having ACPI in an experimental state or relying on distro-only kernel patches. This means that a _mainline_ kernel configured with such ACPI default on option would require an explicit acpi=off on the command line to boot with DT. Since you don't always know which kernel you'd run, you pretty much end up with an acpi= option on the command line permanently.
Maybe those vendors providing both ACPI and DT have a good reason like ACPI support not ready.
Quoted 4 lines
I would much rather be able to configure the kernel to prefer (or even unconditionally require) ACPI to boot, as this will be the normal, default, and only supported way to boot for our platform, and I expect this to also be the case in much of the enterprise space.
I really don't care about which platform recommends ACPI or DT. What I care about is not having to enable certain config option depending on which platform you target as this leads to config fragmentation (think of single Image). I much prefer a clear kernel policy on whether ACPI or DT is used if both are provided by firmware and we've already made that call - DT takes precedence.
Quoted 3 lines
Since I don't think it is possible to build an arm64 kernel with only ACPI, and no DT support, I think a kconfig option to select the preferred HW description to be used is the better solution.
The (multi-platform, single Image) kernel is not in a position to assess whether ACPI or DT is in a better state for a given SoC. We should leave this "ACPI preferred" choice to the code running before the kernel by simply providing only ACPI tables.
Catalin Marinas
maintainerPATCH 1/1 arm64: acpi: add a Kconfig option to prefer ACPI boot over DT
Quoted 11 lines · Roy Franz
Quoted 10 lines · Catalin Marinas
Quoted 8 lines · Roy Franz (HPE)
While this is a 'distro preference', I think it is somewhat ugly for
this to be configured on the commandline. We (HPE) don't support DT,
and I don't think that is likely to change. While we control the firmware for our main internal platform, and don't provide a DT there, we also do development and testing on other platforms where the firmware may provide a DT, but we never want to use it. This requires developers/users to specify "acpi=force" on the command-line to boot in a supported manner.
Quoted 7 lines
Quoted 2 lines
You wrongly assume that everyone wants ACPI by generalising "we" (HPE) to "developers/users".
This is not what I am assuming or thinking. I think that a large enough set of arm64 developers and users care primarily/only about ACPI, and would benefit from not having to have an "acpi=xx" on the command-line forevermore.
That's to the detriment of those wanting to use DT on such platforms and would have to pass "acpi=off" (because I don't believe in different kernel images/configurations for different platforms).
You may argue that no-one wants to use DT if the firmware also provides ACPI. As we currently stand, there are two main camps on ARM:
1. The DT one, unlikely to ever bother with ACPI for their platforms (e.g. mobile). This camp never cares about DT vs ACPI preference because their firmware would never provide the latter
2. The ACPI early adopters. Of these, there are two sub-categories:
a) those who care about mainline Linux and provide a DT (in addition to ACPI) with their firmware as the more mature solution
b) those who only run distro kernels with tons of patches and think that ACPI on ARM is ready, the last thing to solve being the boot priority
As maintainer, I only care about (1) and (2.a). When ACPI on ARM will be mature enough and more feature-rich than DT (e.g. RAS features), we can revisit the ACPI vs DT boot priority, potentially making a switch without any additional config options. Who knows, maybe at that point no firmware will provide both DT and ACPI and we won't need to do anything in the kernel.
But in the meantime, from a _mainline_ perspective, DT is considered the recommended/better supported option and the boot preference should only be overridden by users explicitly via command line arguments.
Signature · 1 line
Catalin