From mboxrd@z Thu Jan 1 00:00:00 1970 From: lorenzo.pieralisi@arm.com (Lorenzo Pieralisi) Date: Wed, 3 Sep 2014 17:27:39 +0100 Subject: [PATCH v3 10/17] ACPI / processor: Make it possible to get CPU hardware ID via GICC In-Reply-To: <1409583475-6978-11-git-send-email-hanjun.guo@linaro.org> References: <1409583475-6978-1-git-send-email-hanjun.guo@linaro.org> <1409583475-6978-11-git-send-email-hanjun.guo@linaro.org> Message-ID: <20140903162739.GF1824@e102568-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Hanjun, On Mon, Sep 01, 2014 at 03:57:48PM +0100, Hanjun Guo wrote: > Introduce a new function map_gicc_mpidr() to allow MPIDRs to be obtained > from the GICC Structure introduced by ACPI 5.1. > > MPIDR is the CPU hardware ID as local APIC ID on x86 platform, so we use > MPIDR not the GIC CPU interface ID to identify CPUs. > > Signed-off-by: Hanjun Guo > --- > arch/arm64/include/asm/acpi.h | 32 ++++++++++++++++++++++++++++++++ > arch/arm64/kernel/acpi.c | 1 - > drivers/acpi/processor_core.c | 37 +++++++++++++++++++++++++++++++++++++ > 3 files changed, 69 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h > index e013dbb..a867467 100644 > --- a/arch/arm64/include/asm/acpi.h > +++ b/arch/arm64/include/asm/acpi.h > @@ -12,6 +12,8 @@ > #ifndef _ASM_ACPI_H > #define _ASM_ACPI_H > > +#include > + > /* Basic configuration for ACPI */ > #ifdef CONFIG_ACPI > #define acpi_strict 1 /* No out-of-spec workarounds on ARM64 */ > @@ -38,6 +40,36 @@ static inline void disable_acpi(void) > acpi_noirq = 1; > } > > +/* MPIDR value provided in GICC structure is 64 bits, but > + * the acpi processor driver use the 32 bits cpu hardware > + * ID (apic_id on intel platform) everywhere, it is pretty > + * hard to modify the acpi processor driver to accept the > + * 64 bits MPIDR value, at the same time, only 32 bits of > + * the MPIDR is used in the 64 bits MPIDR, just pack the > + * Affx fields into a single 32 bit identifier to accommodate > + * the acpi processor drivers. > + */ I have comments on the code in this patch, but they are not the most important point. What I am really worried about, it is that as ARM, I do not want to know what an apic_id is. This code is *supposed* to be generic and yet it is chock-full of x86 specific stuff and you are trying to make ARM HW concepts fit with x86 ones, and I am not happy with that. To be clearer, why does not this look-up of: logical-cpu-index -> physical-cpu-index is not carried out using the acpi_id ? Every architecture will have to add arch specific code to carry out the reverse look-up: acpi_id -> apic_id (x86) acpi_id -> mpidr_el1 (arm64) and the code would end up being split in a nice way. On top of that, I wonder why ACPI structures like eg struct acpi_processor contain x86 specific data (ie apic_id). I know it is a HW identifier as the MPIDR_EL1 is on arm64, but I do not want to deal with that in generic ACPI code because that's not generic at ALL. What if another architecture wants to use ACPI ? Are we going to map its HW CPU identifier to an apic_id only because that's what x86 requires ? I am sorry I do not like that. I understand it is easier to map ARM code to existing ACPI structures but I feel we will run into issues very soon because of that. Is it that complex to remove the apic_id dependency in *generic* ACPI code and replace it with functions that hook into arch specific code to carry out the logical to physical cpu mappings ? I understand this is harder to do, but it will make your life easier in the long run. I am thinking of other pieces of code like the supposedly generic ACPI CPUidle driver, where we *still* depend on the apic to detect idle states, this is not going to fly, I am sorry, we need to have code that has a chance to be generic from the beginning not as an afterthought. Lorenzo > +static inline u32 pack_mpidr_into_32_bits(u64 mpidr) > +{ > + /* > + * Bits [0:7] Aff0; > + * Bits [8:15] Aff1; > + * Bits [16:23] Aff2; > + * Bits [32:39] Aff3; > + */ > + return (u32) ((mpidr & 0xff00000000) >> 8) | mpidr; > +} > + > +/* > + * The ACPI processor driver for ACPI core code needs this macro > + * to find out this cpu was already mapped (mapping from CPU hardware > + * ID to CPU logical ID) or not. > + * > + * cpu_logical_map(cpu) is the mapping of MPIDR and the logical cpu, > + * and MPIDR is the cpu hardware ID we needed to pack. > + */ > +#define cpu_physical_id(cpu) pack_mpidr_into_32_bits(cpu_logical_map(cpu)) > + > /* > * It's used from ACPI core in kdump to boot UP system with SMP kernel, > * with this check the ACPI core will not override the CPU index > diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c > index fbaaf01..35dff11 100644 > --- a/arch/arm64/kernel/acpi.c > +++ b/arch/arm64/kernel/acpi.c > @@ -24,7 +24,6 @@ > #include > #include > > -#include > #include > #include > > diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c > index e32321c..4007313 100644 > --- a/drivers/acpi/processor_core.c > +++ b/drivers/acpi/processor_core.c > @@ -64,6 +64,38 @@ static int map_lsapic_id(struct acpi_subtable_header *entry, > return 0; > } > > +/* > + * On ARM platform, MPIDR value is the hardware ID as apic ID > + * on Intel platforms > + */ > +static int map_gicc_mpidr(struct acpi_subtable_header *entry, > + int device_declaration, u32 acpi_id, int *mpidr) > +{ > + struct acpi_madt_generic_interrupt *gicc = > + container_of(entry, struct acpi_madt_generic_interrupt, header); > + > + if (!(gicc->flags & ACPI_MADT_ENABLED)) > + return -ENODEV; > + > + /* In the GIC interrupt model, logical processors are > + * required to have a Processor Device object in the DSDT, > + * so we should check device_declaration here > + */ > + if (device_declaration && (gicc->uid == acpi_id)) { > + /* > + * Only bits [0:7] Aff0, bits [8:15] Aff1, bits [16:23] Aff2 > + * and bits [32:39] Aff3 are meaningful, so pack the Affx > + * fields into a single 32 bit identifier to accommodate the > + * acpi processor drivers. > + */ > + *mpidr = ((gicc->arm_mpidr & 0xff00000000) >> 8) > + | gicc->arm_mpidr; > + return 0; > + } > + > + return -EINVAL; > +} > + > static int map_madt_entry(int type, u32 acpi_id) > { > unsigned long madt_end, entry; > @@ -99,6 +131,9 @@ static int map_madt_entry(int type, u32 acpi_id) > } else if (header->type == ACPI_MADT_TYPE_LOCAL_SAPIC) { > if (!map_lsapic_id(header, type, acpi_id, &apic_id)) > break; > + } else if (header->type == ACPI_MADT_TYPE_GENERIC_INTERRUPT) { > + if (!map_gicc_mpidr(header, type, acpi_id, &apic_id)) > + break; > } > entry += header->length; > } > @@ -131,6 +166,8 @@ static int map_mat_entry(acpi_handle handle, int type, u32 acpi_id) > map_lsapic_id(header, type, acpi_id, &apic_id); > } else if (header->type == ACPI_MADT_TYPE_LOCAL_X2APIC) { > map_x2apic_id(header, type, acpi_id, &apic_id); > + } else if (header->type == ACPI_MADT_TYPE_GENERIC_INTERRUPT) { > + map_gicc_mpidr(header, type, acpi_id, &apic_id); > } > > exit: > -- > 1.7.9.5 > >