Re: [PATCH v3 1/3] hw/i2c: Implement Broadcom Serial Controller (BSC)

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Rayhan,

On 20/2/24 14:41, Rayhan Faizel wrote:
> A few deficiencies in the current device model need to be noted.
> 
> 1. FIFOs are not used. All sends and receives are done directly.
> 2. Repeated starts are not emulated. Repeated starts can be triggered in real
> hardware by sending a new read transfer request in the window time between
> transfer active set of write transfer request and done bit set of the same.
> 
> Signed-off-by: Rayhan Faizel <rayhan.faizel@gmail.com>
> ---
>   docs/system/arm/raspi.rst    |   1 +
>   hw/i2c/Kconfig               |   4 +
>   hw/i2c/bcm2835_i2c.c         | 278 +++++++++++++++++++++++++++++++++++
>   hw/i2c/meson.build           |   1 +
>   include/hw/i2c/bcm2835_i2c.h |  80 ++++++++++
>   5 files changed, 364 insertions(+)
>   create mode 100644 hw/i2c/bcm2835_i2c.c
>   create mode 100644 include/hw/i2c/bcm2835_i2c.h


> new file mode 100644
> index 0000000000..d6b9bf887a
> --- /dev/null
> +++ b/hw/i2c/bcm2835_i2c.c
> @@ -0,0 +1,278 @@
> +/*
> + * Broadcom Serial Controller (BSC)
> + *
> + * Copyright (c) 2024 Rayhan Faizel <rayhan.faizel@gmail.com>
> + *
> + * SPDX-License-Identifier: MIT
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/log.h"
> +#include "hw/i2c/bcm2835_i2c.h"
> +#include "hw/irq.h"
> +#include "migration/vmstate.h"
> +
> +static void bcm2835_i2c_update_interrupt(BCM2835I2CState *s)
> +{
> +    int do_interrupt = 0;
> +    /* Interrupt on RXR (Needs reading) */
> +    if (s->c & BCM2835_I2C_C_INTR && s->s & BCM2835_I2C_S_RXR) {
> +        do_interrupt = 1;
> +    }
> +
> +    /* Interrupt on TXW (Needs writing) */
> +    if (s->c & BCM2835_I2C_C_INTT && s->s & BCM2835_I2C_S_TXW) {
> +        do_interrupt = 1;
> +    }
> +
> +    /* Interrupt on DONE (Transfer complete) */
> +    if (s->c & BCM2835_I2C_C_INTD && s->s & BCM2835_I2C_S_DONE) {
> +        do_interrupt = 1;
> +    }
> +    qemu_set_irq(s->irq, do_interrupt);
> +}
> +
> +static void bcm2835_i2c_begin_transfer(BCM2835I2CState *s)
> +{
> +    int direction = s->c & BCM2835_I2C_C_READ;
> +    if (i2c_start_transfer(s->bus, s->a, direction)) {
> +        s->s |= BCM2835_I2C_S_ERR;
> +    }
> +    s->s |= BCM2835_I2C_S_TA;
> +
> +    if (direction) {
> +        s->s |= BCM2835_I2C_S_RXR | BCM2835_I2C_S_RXD;
> +    } else {
> +        s->s |= BCM2835_I2C_S_TXW;
> +    }
> +}
> +
> +static void bcm2835_i2c_finish_transfer(BCM2835I2CState *s)
> +{
> +    /*
> +     * STOP is sent when DLEN counts down to zero.
> +     *
> +     * https://github.com/torvalds/linux/blob/master/drivers/i2c/busses/i2c-bcm2835.c#L223-L261

Sorry for not reviewing your patches earlier.

Since this documentation will stay for long and the Linux master branch
will change, better use a tag:
https://github.com/torvalds/linux/blob//v6.7/drivers/i2c/busses/i2c-bcm2835.c#L223-L261

Do you mind posting a patch to correct this?

Thanks,

Phil.