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Re: [PATCH v4 18/37] mips: baudbase is 115200 by default
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH v4 18/37] mips: baudbase is 115200 by default |
Date: |
Mon, 25 Nov 2019 13:54:08 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 |
On 11/25/19 12:26 PM, Philippe Mathieu-Daudé wrote:
On 11/25/19 11:12 AM, Marc-André Lureau wrote:
Hi
On Mon, Nov 25, 2019 at 2:07 PM Aleksandar Markovic
<address@hidden> wrote:
On Wednesday, November 20, 2019, Marc-André Lureau
<address@hidden> wrote:
Signed-off-by: Marc-André Lureau <address@hidden>
---
hw/mips/mips_mipssim.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/hw/mips/mips_mipssim.c b/hw/mips/mips_mipssim.c
index bfafa4d7e9..3cd0e6eb33 100644
--- a/hw/mips/mips_mipssim.c
+++ b/hw/mips/mips_mipssim.c
@@ -223,7 +223,6 @@ mips_mipssim_init(MachineState *machine)
if (serial_hd(0)) {
DeviceState *dev = qdev_create(NULL, TYPE_SERIAL_IO);
- qdev_prop_set_uint32(DEVICE(dev), "baudbase", 115200);
qdev_prop_set_chr(dev, "chardev", serial_hd(0));
qdev_set_legacy_instance_id(dev, 0x3f8, 2);
qdev_init_nofail(dev);
--
Please mention in your commit message where the default baudbase is set.
ok
Also, is there a guarantie that default value 115200 will never
change in future?
The level of stability on properties in general is unclear to me.
Given that 115200 is standard for serial, it is unlikely to change
though.. We can have an assert there instead?
Peter, what do you think? thanks
This property confused me by the past. It is _not_ the baudrate.
It is the input frequency clocking the UART ('XIN' pin, Xtal INput).
Each board has its own frequency, and it can even be variable (the clock
domain tree can reconfigure it at a different rate).
Laurent pointed me to the following commit which confirms my interpretation:
$ git show 038eaf82c853
commit 038eaf82c853f3bf8d4c106c0677bbf4adada7de
Author: Stefan Weil <address@hidden>
Date: Sat Oct 31 11:28:11 2009 +0100
serial: Add interface to set reference oscillator frequency
Many (most?) serial interfaces have a programmable
clock which provides the reference frequency ("baudbase").
So a fixed baudbase which is only set once can be wrong.
omap1.c is an example which could use the new interface
to change baudbase when the programmable clock changes.
ar7 system emulation (still not part of standard QEMU)
is similar to omap and already uses serial_set_frequency.
Signed-off-by: Stefan Weil <address@hidden>
Signed-off-by: Anthony Liguori <address@hidden>
diff --git a/hw/pc.h b/hw/pc.h
index 15fff8d103..03ffc91536 100644
--- a/hw/pc.h
+++ b/hw/pc.h
@@ -13,6 +13,7 @@ SerialState *serial_mm_init (target_phys_addr_t base,
int it_shift,
qemu_irq irq, int baudbase,
CharDriverState *chr, int ioregister);
SerialState *serial_isa_init(int index, CharDriverState *chr);
+void serial_set_frequency(SerialState *s, uint32_t frequency);
/* parallel.c */
diff --git a/hw/serial.c b/hw/serial.c
index fa12dcc075..0063260569 100644
--- a/hw/serial.c
+++ b/hw/serial.c
@@ -730,6 +730,13 @@ static void serial_init_core(SerialState *s)
serial_event, s);
}
+/* Change the main reference oscillator frequency. */
+void serial_set_frequency(SerialState *s, uint32_t frequency)
+{
+ s->baudbase = frequency;
+ serial_update_parameters(s);
+}
+
- Re: [PATCH v4 17/37] mips: inline serial_init(), (continued)
Re: [PATCH v4 17/37] mips: inline serial_init(), Aleksandar Markovic, 2019/11/27
[PATCH v4 18/37] mips: baudbase is 115200 by default, Marc-André Lureau, 2019/11/20
- Re: [PATCH v4 18/37] mips: baudbase is 115200 by default, Peter Maydell, 2019/11/21
- Re: [PATCH v4 18/37] mips: baudbase is 115200 by default, Aleksandar Markovic, 2019/11/25
- Re: [PATCH v4 18/37] mips: baudbase is 115200 by default, Marc-André Lureau, 2019/11/25
- Re: [PATCH v4 18/37] mips: baudbase is 115200 by default, Philippe Mathieu-Daudé, 2019/11/25
- Re: [PATCH v4 18/37] mips: baudbase is 115200 by default, Aleksandar Markovic, 2019/11/25
- Re: [PATCH v4 18/37] mips: baudbase is 115200 by default,
Philippe Mathieu-Daudé <=
- Re: [PATCH v4 18/37] mips: baudbase is 115200 by default, Philippe Mathieu-Daudé, 2019/11/25
- Re: [PATCH v4 18/37] mips: baudbase is 115200 by default, Marc-André Lureau, 2019/11/27
- Re: [PATCH v4 18/37] mips: baudbase is 115200 by default, Aleksandar Markovic, 2019/11/27
[PATCH v4 19/37] mips: use sysbus_add_io(), Marc-André Lureau, 2019/11/20
[PATCH v4 20/37] mips: use sysbus_mmio_get_region() instead of internal fields, Marc-André Lureau, 2019/11/20
[PATCH v4 21/37] sm501: make SerialMM a child, export chardev property, Marc-André Lureau, 2019/11/20