From: "Philippe Mathieu-Daudé" <philmd@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: "Inès Varhol" <ines.varhol@telecom-paris.fr>,
qemu-devel@nongnu.org, qemu-arm@nongnu.org,
"Thomas Huth" <thuth@redhat.com>,
"Arnaud Minier" <arnaud.minier@telecom-paris.fr>,
"Laurent Vivier" <lvivier@redhat.com>,
"Marc-André Lureau" <marcandre.lureau@redhat.com>,
"Alistair Francis" <alistair@alistair23.me>,
"Samuel Tardieu" <samuel.tardieu@telecom-paris.fr>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Markus Armbruster" <armbru@redhat.com>
Subject: Re: [PATCH 3/4] hw/char: Add QOM property for STM32L4x5 USART clock frequency
Date: Wed, 8 May 2024 16:08:45 +0200 [thread overview]
Message-ID: <d03ca96e-53e9-43ed-886e-0cffd15994fb@linaro.org> (raw)
In-Reply-To: <CAFEAcA83cgqq3yh3=d=gHd-LK3qh2g-pE2v734apKmcNTJTvww@mail.gmail.com>
Hi,
On 7/5/24 11:54, Peter Maydell wrote:
> On Mon, 6 May 2024 at 10:34, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>>
>> Hi,
>>
>> On 5/5/24 16:05, Inès Varhol wrote:
>>> Signed-off-by: Inès Varhol <ines.varhol@telecom-paris.fr>
>>> ---
>>> hw/char/stm32l4x5_usart.c | 12 ++++++++++++
>>> 1 file changed, 12 insertions(+)
>>>
>>> diff --git a/hw/char/stm32l4x5_usart.c b/hw/char/stm32l4x5_usart.c
>>> index fc5dcac0c4..ee7727481c 100644
>>> --- a/hw/char/stm32l4x5_usart.c
>>> +++ b/hw/char/stm32l4x5_usart.c
>>> @@ -26,6 +26,7 @@
>>> #include "hw/clock.h"
>>> #include "hw/irq.h"
>>> #include "hw/qdev-clock.h"
>>> +#include "qapi/visitor.h"
>>> #include "hw/qdev-properties.h"
>>> #include "hw/qdev-properties-system.h"
>>> #include "hw/registerfields.h"
>>> @@ -523,6 +524,14 @@ static Property stm32l4x5_usart_base_properties[] = {
>>> DEFINE_PROP_END_OF_LIST(),
>>> };
>>>
>>> +static void clock_freq_get(Object *obj, Visitor *v,
>>> + const char *name, void *opaque, Error **errp)
>>> +{
>>> + Stm32l4x5UsartBaseState *s = STM32L4X5_USART_BASE(obj);
>>> + uint32_t clock_freq_hz = clock_get_hz(s->clk);
>>> + visit_type_uint32(v, name, &clock_freq_hz, errp);
>>> +}
>>> +
>>> static void stm32l4x5_usart_base_init(Object *obj)
>>> {
>>> Stm32l4x5UsartBaseState *s = STM32L4X5_USART_BASE(obj);
>>> @@ -534,6 +543,9 @@ static void stm32l4x5_usart_base_init(Object *obj)
>>> sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
>>>
>>> s->clk = qdev_init_clock_in(DEVICE(s), "clk", NULL, s, 0);
>>> +
>>> + object_property_add(obj, "clock-freq-hz", "uint32",
>>> + clock_freq_get, NULL, NULL, NULL);
>>
>> Patch LGTM, but I wonder if registering QOM getter without setter
>> is recommended. Perhaps we should encourage parity? In normal HW
>> emulation we shouldn't update this clock externally, but thinking
>> about testing, this could be interesting to introduce jitter.
>
> object_property_add() with the set function NULL is fine,
> and is documented to mean "property cannot be set". Attempts
> to set it will be failed (in object_property_set()) with a
> reasonable error.
>
> But it's not clear to me why we want the property in the first
> place -- we don't generally have devices which take a Clock
> input have properties exposing its frequency. If we did want
> that it would probably be better if we could do it generically
> rather than by adding more boilerplate code to each device.
Inès qtest checking (via HMP) the configured clock has a
correct scaled frequency seems a good use case.
> Mostly "frequency" properties on devices are for the case
> where they *don't* have a Clock input and instead have
> ad-hoc legacy handling where the board/SoC that creates the
> device sets an integer property to define the input frequency
> because it doesn't model the clock tree with Clock objects.
>
> thanks
> -- PMM
next prev parent reply other threads:[~2024-05-08 14:09 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-05 14:05 [PATCH 0/4] Check clock connection between STM32L4x5 RCC and peripherals Inès Varhol
2024-05-05 14:05 ` [PATCH 1/4] hw/misc: Create STM32L4x5 SYSCFG clock Inès Varhol
2024-05-07 9:50 ` Peter Maydell
2024-05-07 17:30 ` Inès Varhol
2024-05-05 14:05 ` [PATCH 2/4] hw/gpio: Handle clock migration in STM32L4x5 gpios Inès Varhol
2024-05-06 9:38 ` Philippe Mathieu-Daudé
2024-05-05 14:05 ` [PATCH 3/4] hw/char: Add QOM property for STM32L4x5 USART clock frequency Inès Varhol
2024-05-06 9:34 ` Philippe Mathieu-Daudé
2024-05-06 9:43 ` Philippe Mathieu-Daudé
2024-05-07 9:54 ` Peter Maydell
2024-05-08 14:08 ` Philippe Mathieu-Daudé [this message]
2024-05-05 14:05 ` [PATCH 4/4] tests/qtest: Check STM32L4x5 clock connections Inès Varhol
2024-05-06 4:16 ` Thomas Huth
2024-05-06 17:57 ` Inès Varhol
-- strict thread matches above, loose matches on Subject: below --
2024-05-07 18:55 [PATCH 0/4] Check clock connection between STM32L4x5 RCC and peripherals Inès Varhol
2024-05-07 18:55 ` [PATCH 3/4] hw/char: Add QOM property for STM32L4x5 USART clock frequency Inès Varhol
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