linux-kernel - [PATCH v2 0/1] arm: topology: parse the topology from the dt

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Date:   Wed, 14 Apr 2021 20:23:25 +0800
From:   Ruifeng Zhang <ruifeng.zhang0110@...il.com>
To:     linux@...linux.org.uk, sudeep.holla@....com,
        gregkh@...uxfoundation.org, rafael@...nel.org,
        a.p.zijlstra@...llo.nl, dietmar.eggemann@....com, mingo@...nel.org,
        valentin.schneider@....com, ruifeng.zhang1@...soc.com,
        nianfu.bai@...soc.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/1] arm: topology: parse the topology from the dt

From: Ruifeng Zhang <ruifeng.zhang1@...soc.com>

In Unisoc, the sc9863a SoC which using cortex-a55, it has two software
version, one of them is the kernel running on EL1 using aarch32.
                user(EL0)             kernel(EL1)
sc9863a_go      aarch32               aarch32
sc9863a         aarch64               aarch64

When kernel runs on EL1 using aarch32, the topology will parse wrong.
For example,
The MPIDR has been written to the chip register in armv8.2 format.
For example,
core0: 0000000080000000
core1: 0000000080000100
core2: 0000000080000200
...

It will parse to:
|       | aff2 | packageid | coreid |
|-------+------+-----------+--------|
| Core0 |    0 |         0 |    0   |
| Core1 |    0 |         1 |    0   |
| Core2 |    0 |         2 |    0   |
|  ...  |      |           |        |

The wrong topology is that all of the coreid are 0 and unexpected
packageid.

The reason is the MPIDR format is different between armv7 and armv8.2.
armv7 (A7) mpidr is:
[11:8]      [7:2]       [1:0]
cluster     reserved    cpu
The cortex-a7 spec DDI0464F 4.3.5
https://developer.arm.com/documentation/ddi0464/f/?lang=en

armv8.2 (A55) mpidr is:
[23:16]     [15:8]      [7:0]
cluster     cpu         thread

The current arch/arm/kernel/topology code parse the MPIDR with a armv7
format. The parse code is:
void store_cpu_topology(unsigned int cpuid)
{
    ...
    cpuid_topo->thread_id = -1;
    cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
    cpuid_topo->package_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
    ...
}

Ruifeng Zhang (1):
  arm: topology: parse the topology from the dt

 arch/arm/kernel/topology.c    | 22 ++++++----------------
 drivers/base/arch_topology.c  |  4 ++--
 include/linux/arch_topology.h |  1 +
 3 files changed, 9 insertions(+), 18 deletions(-)

-- 
2.17.1