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From: Christoph Hellwig <hch@lst.de>
To: Palmer Dabbelt <palmer@sifive.com>,
	Paul Walmsley <paul.walmsley@sifive.com>
Cc: Atish Patra <atish.patra@wdc.com>,
	Damien Le Moal <Damien.LeMoal@wdc.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 10/15] riscv: read the hart ID from mhartid on boot
Date: Thu, 17 Oct 2019 19:37:38 +0200	[thread overview]
Message-ID: <20191017173743.5430-11-hch@lst.de> (raw)
In-Reply-To: <20191017173743.5430-1-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 679e63d29edb..583784cb3a32 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


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  parent reply	other threads:[~2019-10-17 17:38 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-17 17:37 RISC-V nommu support v5 Christoph Hellwig
2019-10-17 17:37 ` [PATCH 01/15] riscv: cleanup <asm/bug.h> Christoph Hellwig
2019-10-18  2:50   ` Anup Patel
2019-10-23 22:04   ` Paul Walmsley
2019-10-17 17:37 ` [PATCH 02/15] riscv: cleanup do_trap_break Christoph Hellwig
2019-10-18  2:51   ` Anup Patel
2019-10-23 22:05   ` Paul Walmsley
2019-10-17 17:37 ` [PATCH 03/15] riscv: abstract out CSR names for supervisor vs machine mode Christoph Hellwig
2019-10-18  2:51   ` Anup Patel
2019-10-18 23:55   ` Paul Walmsley
2019-10-28  8:12     ` Christoph Hellwig
2019-10-17 17:37 ` [PATCH 04/15] riscv: don't allow selecting SBI based drivers for M-mode Christoph Hellwig
2019-10-18  2:52   ` Anup Patel
2019-10-17 17:37 ` [PATCH 05/15] riscv: poison SBI calls " Christoph Hellwig
2019-10-18  2:53   ` Anup Patel
2019-10-17 17:37 ` [PATCH 06/15] riscv: cleanup the default power off implementation Christoph Hellwig
2019-10-18  2:53   ` Anup Patel
2019-10-17 17:37 ` [PATCH 07/15] riscv: implement remote sfence.i using IPIs Christoph Hellwig
2019-10-18  2:55   ` Anup Patel
2019-10-17 17:37 ` [PATCH 08/15] riscv: add support for MMIO access to the timer registers Christoph Hellwig
2019-10-18  2:57   ` Anup Patel
2019-10-17 17:37 ` [PATCH 09/15] riscv: provide native clint access for M-mode Christoph Hellwig
2019-10-18  3:00   ` Anup Patel
2019-11-14  7:39   ` Paul Walmsley
2019-10-17 17:37 ` Christoph Hellwig [this message]
2019-10-18  3:01   ` [PATCH 10/15] riscv: read the hart ID from mhartid on boot Anup Patel
2019-11-14  7:40   ` Paul Walmsley
2019-10-17 17:37 ` [PATCH 11/15] riscv: use the correct interrupt levels for M-mode Christoph Hellwig
2019-10-18  3:01   ` Anup Patel
2019-10-17 17:37 ` [PATCH 12/15] riscv: clear the instruction cache and all registers when booting Christoph Hellwig
2019-10-18  3:05   ` Anup Patel
2019-10-17 17:37 ` [PATCH 13/15] riscv: add nommu support Christoph Hellwig
2019-10-18  3:04   ` Anup Patel
2019-10-17 17:37 ` [PATCH 14/15] riscv: provide a flat image loader Christoph Hellwig
2019-10-18  3:06   ` Anup Patel
2019-10-17 17:37 ` [PATCH 15/15] riscv: disable the EFI PECOFF header for M-mode Christoph Hellwig
2019-10-18  3:06   ` Anup Patel
2019-10-18  3:08 ` RISC-V nommu support v5 Anup Patel
2019-10-18  3:29   ` Paul Walmsley
2019-10-18 15:25     ` Christoph Hellwig
2019-10-18 23:46       ` Paul Walmsley

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