From: Christoph Hellwig <hch@lst.de>
To: Palmer Dabbelt <palmer@sifive.com>,
Paul Walmsley <paul.walmsley@sifive.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
Damien Le Moal <Damien.LeMoal@wdc.com>,
Atish Patra <atish.patra@wdc.com>
Subject: [PATCH 15/20] riscv: read the hart ID from mhartid on boot
Date: Tue, 3 Sep 2019 11:32:34 +0200 [thread overview]
Message-ID: <20190903093239.21278-16-hch@lst.de> (raw)
In-Reply-To: <20190903093239.21278-1-hch@lst.de>
From: Damien Le Moal <Damien.LeMoal@wdc.com>
When in M-Mode, we can use the mhartid CSR to get the ID of the running
HART. Doing so, direct M-Mode boot without firmware is possible.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
arch/riscv/include/asm/csr.h | 1 +
arch/riscv/kernel/head.S | 8 ++++++++
2 files changed, 9 insertions(+)
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 0dae5c361f29..d0b5113e1a54 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -81,6 +81,7 @@
#define SIE_SEIE (_AC(0x1, UL) << IRQ_S_EXT)
/* symbolic CSR names: */
+#define CSR_MHARTID 0xf14
#define CSR_MSTATUS 0x300
#define CSR_MIE 0x304
#define CSR_MTVEC 0x305
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index bb96bb7b95d2..e0350499d7a4 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -50,6 +50,14 @@ _start_kernel:
csrw CSR_XIE, zero
csrw CSR_XIP, zero
+#ifdef CONFIG_RISCV_M_MODE
+ /*
+ * The hartid in a0 is expected later on, and we have no firmware
+ * to hand it to us.
+ */
+ csrr a0, CSR_MHARTID
+#endif
+
/* Load the global pointer */
.option push
.option norelax
--
2.20.1
next prev parent reply other threads:[~2019-09-03 9:33 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-03 9:32 RISC-V nommu support v4 Christoph Hellwig
2019-09-03 9:32 ` [PATCH 01/20] irqchip/sifive-plic: set max threshold for ignored handlers Christoph Hellwig
2019-09-03 9:32 ` [PATCH 02/20] riscv: refactor the IPI code Christoph Hellwig
2019-09-03 9:32 ` [PATCH 03/20] riscv: cleanup send_ipi_mask Christoph Hellwig
2019-09-03 9:32 ` [PATCH 04/20] riscv: optimize send_ipi_single Christoph Hellwig
2019-09-03 9:32 ` [PATCH 05/20] riscv: cleanup riscv_cpuid_to_hartid_mask Christoph Hellwig
2019-09-03 9:32 ` [PATCH 06/20] riscv: don't use the rdtime(h) pseudo-instructions Christoph Hellwig
2019-09-03 9:32 ` [PATCH 07/20] riscv: move the TLB flush logic out of line Christoph Hellwig
2019-09-03 9:32 ` [PATCH 08/20] riscv: abstract out CSR names for supervisor vs machine mode Christoph Hellwig
2019-10-16 2:07 ` Paul Walmsley
2019-10-17 16:20 ` Christoph Hellwig
2019-09-03 9:32 ` [PATCH 09/20] riscv: don't allow selecting SBI based drivers for M-mode Christoph Hellwig
2019-09-03 9:32 ` [PATCH 10/20] riscv: poison SBI calls " Christoph Hellwig
2019-09-03 9:32 ` [PATCH 11/20] riscv: cleanup the default power off implementation Christoph Hellwig
2019-09-03 9:32 ` [PATCH 12/20] riscv: implement remote sfence.i using IPIs Christoph Hellwig
2019-09-03 9:32 ` [PATCH 13/20] riscv: add support for MMIO access to the timer registers Christoph Hellwig
2019-09-03 9:32 ` [PATCH 14/20] riscv: provide native clint access for M-mode Christoph Hellwig
2019-09-03 9:32 ` Christoph Hellwig [this message]
2019-09-03 9:32 ` [PATCH 16/20] riscv: use the correct interrupt levels " Christoph Hellwig
2019-09-03 9:32 ` [PATCH 17/20] riscv: clear the instruction cache and all registers when booting Christoph Hellwig
2019-09-03 9:32 ` [PATCH 18/20] riscv: add nommu support Christoph Hellwig
2019-09-03 9:32 ` [PATCH 19/20] riscv: provide a flat image loader Christoph Hellwig
2019-09-03 9:32 ` [PATCH 20/20] riscv: disable the EFI PECOFF header for M-mode Christoph Hellwig
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