QEMU-Devel Archive on lore.kernel.org
 help / color / Atom feed
From: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
To: qemu-devel@nongnu.org
Cc: "Aleksandar Rikalo" <aleksandar.rikalo@syrmia.com>,
	"Paul Burton" <paulburton@kernel.org>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
	"Hervé Poussineau" <hpoussin@reactos.org>,
	"Huacai Chen" <chenhc@lemote.com>,
	"Aurelien Jarno" <aurelien@aurel32.net>
Subject: [PULL 16/44] target/mips/cp0_timer: Document TIMER_PERIOD origin
Date: Sat, 17 Oct 2020 16:02:15 +0200
Message-ID: <20201017140243.1078718-17-f4bug@amsat.org> (raw)
In-Reply-To: <20201017140243.1078718-1-f4bug@amsat.org>

TIMER_PERIOD value of '10 ns' can be explained looking at
commit 6af0bf9c7c3doc, where the CPU frequency is 200 MHz
and CP0 default count rate is half the frequency of the
CPU. Document that.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201012095804.3335117-8-f4bug@amsat.org>
---
 target/mips/cp0_timer.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/target/mips/cp0_timer.c b/target/mips/cp0_timer.c
index 5194c967ae3..6fec5fe0ff7 100644
--- a/target/mips/cp0_timer.c
+++ b/target/mips/cp0_timer.c
@@ -27,7 +27,17 @@
 #include "sysemu/kvm.h"
 #include "internal.h"
 
-#define TIMER_PERIOD 10 /* 10 ns period for 100 Mhz frequency */
+/*
+ * Since commit 6af0bf9c7c3 this model assumes a CPU clocked at 200MHz
+ * and a CP0 timer running at half the clock of the CPU (cp0_count_rate = 2).
+ *
+ * TIMER_FREQ_HZ = CPU_FREQ_HZ / CP0_COUNT_RATE = 200 MHz / 2 = 100 MHz
+ *
+ * TIMER_PERIOD_NS = 1 / TIMER_FREQ_HZ = 10 ns
+ */
+#define CPU_FREQ_HZ_DEFAULT     200000000
+#define CP0_COUNT_RATE_DEFAULT  2
+#define TIMER_PERIOD            10  /* 1 / (CPU_FREQ_HZ / CP0_COUNT_RATE) */
 
 /* MIPS R4K timer */
 static void cpu_mips_timer_update(CPUMIPSState *env)
-- 
2.26.2



  parent reply index

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-17 14:01 [PULL 00/44] mips-next patches for 2020-10-17 Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 01/44] util/cutils: Introduce freq_to_str() to display Hertz units Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 02/44] hw/qdev-clock: Display error hint when clock is missing from device Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 03/44] hw/core/clock: Add the clock_new helper function Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 04/44] target/mips: Fix some comment spelling errors Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 05/44] target/mips: Demacro helpers for <ABS|CHS>.<D|S|PS> Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 06/44] target/mips: Demacro helpers for M<ADD|SUB>F.<D|S> Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 07/44] target/mips: Demacro helpers for <MAX|MAXA|MIN|MINA>.<D|S> Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 08/44] target/mips: Add loongson-ext lswc2 group of instructions (Part 1) Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 09/44] target/mips: Add loongson-ext lswc2 group of instructions (Part 2) Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 10/44] target/mips: Add loongson-ext lsdc2 group of instructions Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 11/44] target/mips/op_helper: Convert multiple if() to switch case Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 12/44] target/mips/op_helper: Document Invalidate/Writeback opcodes as no-op Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 13/44] target/mips/op_helper: Log unimplemented cache opcode Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 14/44] target/mips: Move cpu_mips_get_random() with CP0 helpers Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 15/44] target/mips/cp0_timer: Explicit unit in variable name Philippe Mathieu-Daudé
2020-10-17 14:02 ` Philippe Mathieu-Daudé [this message]
2020-10-17 14:02 ` [PULL 17/44] target/mips: Move cp0_count_ns to CPUMIPSState Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 18/44] target/mips/cpu: Calculate the CP0 timer period using the CPU frequency Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 19/44] target/mips/cpu: Make cp0_count_rate a property Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 20/44] target/mips/cpu: Allow the CPU to use dynamic frequencies Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 21/44] target/mips/cpu: Introduce mips_cpu_create_with_clock() helper Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 22/44] hw/mips/r4k: Explicit CPU frequency is 200 MHz Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 23/44] hw/mips/fuloong2e: Set CPU frequency to 533 MHz Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 24/44] hw/mips/mipssim: Correct CPU frequency Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 25/44] hw/mips/jazz: Correct CPU frequencies Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 26/44] hw/mips/cps: Expose input clock and connect it to CPU cores Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 27/44] hw/mips/boston: Set CPU frequency to 1 GHz Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 28/44] hw/mips/malta: Set CPU frequency to 320 MHz Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 29/44] hw/mips/cps: Do not allow use without input clock Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 30/44] target/mips/cpu: Display warning when CPU is used " Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 31/44] hw/mips/malta: Fix FPGA I/O region size Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 32/44] hw/mips/malta: Move gt64120 related code together Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 33/44] hw/mips/malta: Use clearer qdev style Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 34/44] hw/mips: Simplify loading 64-bit ELF kernels Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 35/44] hw/mips: Simplify code using ROUND_UP(INITRD_PAGE_SIZE) Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 36/44] hw/mips: Rename TYPE_MIPS_BOSTON to TYPE_BOSTON Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 37/44] hw/mips: Remove exit(1) in case of missing ROM Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 38/44] tests/acceptance: Add MIPS record/replay tests Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 39/44] docs/system: Update MIPS CPU documentation Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 40/44] MAINTAINERS: Remove myself Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 41/44] MAINTAINERS: Put myself forward for MIPS target Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 42/44] MAINTAINERS: Downgrade MIPS Boston to 'Odd Fixes', fix Paul Burton mail Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 43/44] MAINTAINERS: Remove duplicated Malta test entries Philippe Mathieu-Daudé
2020-10-17 14:02 ` [PULL 44/44] target/mips: Increase number of TLB entries on the 34Kf core (16 -> 64) Philippe Mathieu-Daudé
2020-10-19 10:45 ` [PULL 00/44] mips-next patches for 2020-10-17 Peter Maydell

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201017140243.1078718-17-f4bug@amsat.org \
    --to=f4bug@amsat.org \
    --cc=aleksandar.rikalo@syrmia.com \
    --cc=aurelien@aurel32.net \
    --cc=chenhc@lemote.com \
    --cc=hpoussin@reactos.org \
    --cc=paulburton@kernel.org \
    --cc=qemu-devel@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

QEMU-Devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/qemu-devel/0 qemu-devel/git/0.git
	git clone --mirror https://lore.kernel.org/qemu-devel/1 qemu-devel/git/1.git
	git clone --mirror https://lore.kernel.org/qemu-devel/2 qemu-devel/git/2.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 qemu-devel qemu-devel/ https://lore.kernel.org/qemu-devel \
		qemu-devel@nongnu.org
	public-inbox-index qemu-devel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.nongnu.qemu-devel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git