Re: [PATCH v10 1/5] staging: vc04_services: vchiq_arm: Add new bus type and device type

[Umang Jain <umang.jain@xxxxxxxxxxxxxxxx>]

Hi Stephan

On 9/12/23 1:52 AM, Stefan Wahren wrote:
> Hi Umang,
>
> Am 11.09.23 um 16:07 schrieb Umang Jain:
> > The devices that the vchiq interface registers (bcm2835-audio,
> > bcm2835-camera) are implemented and exposed by the VC04 firmware.
> > The device tree describes the VC04 itself with the resources required
> > to communicate with it through a mailbox interface. However, the
> > vchiq interface registers these devices as platform devices. This
> > also means the specific drivers for these devices are getting
> > registered as platform drivers. This is not correct and a blatant
> > abuse of platform device/driver.
> >
> > Add a new bus type, vchiq_bus_type and device type (struct vchiq_device)
> > which will be used to migrate child devices that the vchiq interfaces
> > creates/registers from the platform device/driver.
> >
> > Signed-off-by: Umang Jain <umang.jain@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/staging/vc04_services/Makefile        |   1 +
> >   .../interface/vchiq_arm/vchiq_device.c        | 111 ++++++++++++++++++
> >   .../interface/vchiq_arm/vchiq_device.h        |  54 +++++++++
> >   3 files changed, 166 insertions(+)
> >   create mode 100644 
> > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
> >   create mode 100644 
> > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.h
> >
> > diff --git a/drivers/staging/vc04_services/Makefile 
> > b/drivers/staging/vc04_services/Makefile
> > index 44794bdf6173..2d071e55e175 100644
> > --- a/drivers/staging/vc04_services/Makefile
> > +++ b/drivers/staging/vc04_services/Makefile
> > @@ -5,6 +5,7 @@ vchiq-objs := \
> >      interface/vchiq_arm/vchiq_core.o  \
> >      interface/vchiq_arm/vchiq_arm.o \
> >      interface/vchiq_arm/vchiq_debugfs.o \
> > +   interface/vchiq_arm/vchiq_device.o \
> >      interface/vchiq_arm/vchiq_connected.o \
> >
> >   ifdef CONFIG_VCHIQ_CDEV
> > diff --git 
> > a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c 
> > b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
> > new file mode 100644
> > index 000000000000..aad55c461905
> > --- /dev/null
> > +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
> > @@ -0,0 +1,111 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * vchiq_device.c - VCHIQ generic device and bus-type
> > + *
> > + * Copyright (c) 2023 Ideas On Board Oy
> > + */
> > +
> > +#include <linux/device/bus.h>
> > +#include <linux/dma-mapping.h>
> > +#include <linux/of_device.h>
> > +#include <linux/slab.h>
> > +#include <linux/string.h>
> > +
> > +#include "vchiq_device.h"
> > +
> > +static int vchiq_bus_type_match(struct device *dev, struct 
> > device_driver *drv)
> > +{
> > +    if (dev->bus == &vchiq_bus_type &&
> > +        strcmp(dev_name(dev), drv->name) == 0)
> > +        return 1;
> > +
> > +    return 0;
> > +}
> > +
> > +static int vchiq_bus_uevent(const struct device *dev, struct 
> > kobj_uevent_env *env)
> > +{
> > +    const struct vchiq_device *device = container_of_const(dev, 
> > struct vchiq_device, dev);
> > +
> > +    return add_uevent_var(env, "MODALIAS=%s", dev_name(&device->dev));
> > +}
> > +
> > +static int vchiq_bus_probe(struct device *dev)
> > +{
> > +    struct vchiq_device *device = to_vchiq_device(dev);
> > +    struct vchiq_driver *driver = to_vchiq_driver(dev->driver);
> > +    int ret;
> > +
> > +    ret = driver->probe(device);
> > +    if (ret == 0)
> > +        return 0;
> > +
> > +    return ret;
> > +}
> > +
> > +struct bus_type vchiq_bus_type = {
> > +    .name   = "vchiq-bus",
> > +    .match  = vchiq_bus_type_match,
> > +    .uevent = vchiq_bus_uevent,
> > +    .probe  = vchiq_bus_probe,
> > +};
> > +
> > +static void vchiq_device_release(struct device *dev)
> > +{
> > +    struct vchiq_device *device = to_vchiq_device(dev);
> > +
> > +    kfree(device);
> > +}
> > +
> > +struct vchiq_device *
> > +vchiq_device_register(struct device *parent, const char *name)
> > +{
> > +    struct vchiq_device *device;
> > +    int ret;
> > +
> > +    device = kzalloc(sizeof(*device), GFP_KERNEL);
> > +    if (!device) {
> > +        dev_err(parent, "Cannot register %s: Insufficient memory\n",
> > +            name);
> > +        return NULL;
> > +    }
> > +
> > +    device->dev.init_name = name;
> > +    device->dev.parent = parent;
> > +    device->dev.bus = &vchiq_bus_type;
> > +    device->dev.release = vchiq_device_release;
> > +
> > +    of_dma_configure(&device->dev, parent->of_node, true);
> > +    ret = dma_set_mask_and_coherent(&device->dev, DMA_BIT_MASK(32));
> > +    if (ret) {
> > +        dev_err(&device->dev, "32-bit DMA enable failed\n");
> > +        return NULL;
> > +    }
>
> Unfortunately the call of of_dma_configure() generates warnings likes
> this (Raspberry Pi 3A+ with multi_v7_defconfig + VCHIQ):
>
> [    9.206802] vchiq-bus bcm2835-audio: DMA mask not set
> [    9.206892] vchiq-bus bcm2835-camera: DMA mask not set

huh, really weird, as on my RPi-3-b I get these set correctly and I 
don't any such warning.

I am even checking the ret value here, so if it can't set it, it will 
log an error. I don't that getting logged on my end. Can you share you 
entire dmesg output please?

Also, I have tested this against arm64 kernel, I assume you are using 
32-bit?

> In the old platform driver code we had something like
>
>   pdevinfo.dma_mask = DMA_BIT_MASK(32);
>
> So there is still something missing for our new bus driver.

> > +
> > +    ret = device_register(&device->dev);
> > +    if (ret) {
> > +        dev_err(parent, "Cannot register %s: %d\n", name, ret);
> > +        put_device(&device->dev);
> > +        return NULL;
> > +    }
> > +
> > +    return device;
> > +}
> > +
> > +void vchiq_device_unregister(struct vchiq_device *vchiq_dev)
> > +{
> > +    device_unregister(&vchiq_dev->dev);
> > +}
> > +
> > +int vchiq_driver_register(struct vchiq_driver *vchiq_drv)
> > +{
> > +    vchiq_drv->driver.bus = &vchiq_bus_type;
> > +
> > +    return driver_register(&vchiq_drv->driver);
> > +}
> > +EXPORT_SYMBOL_GPL(vchiq_driver_register);
> > +
> > +void vchiq_driver_unregister(struct vchiq_driver *vchiq_drv)
> > +{
> > +    driver_unregister(&vchiq_drv->driver);
> > +}
> > +EXPORT_SYMBOL_GPL(vchiq_driver_unregister);
> > diff --git 
> > a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.h 
> > b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.h
> > new file mode 100644
> > index 000000000000..7eaaf9a91cda
> > --- /dev/null
> > +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.h
> > @@ -0,0 +1,54 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (c) 2023 Ideas On Board Oy
> > + */
> > +
> > +#ifndef _VCHIQ_DEVICE_H
> > +#define _VCHIQ_DEVICE_H
> > +
> > +#include <linux/device.h>
> > +
> > +struct vchiq_device {
> > +    struct device dev;
> > +};
> > +
> > +struct vchiq_driver {
> > +    int        (*probe)(struct vchiq_device *device);
> > +    void        (*remove)(struct vchiq_device *device);
> > +    int        (*resume)(struct vchiq_device *device);
> > +    int        (*suspend)(struct vchiq_device *device,
> > +                   pm_message_t state);
> > +    struct device_driver driver;
> > +};
> > +
> > +static inline struct vchiq_device *to_vchiq_device(struct device *d)
> > +{
> > +    return container_of(d, struct vchiq_device, dev);
> > +}
> > +
> > +static inline struct vchiq_driver *to_vchiq_driver(struct 
> > device_driver *d)
> > +{
> > +    return container_of(d, struct vchiq_driver, driver);
> > +}
> > +
> > +extern struct bus_type vchiq_bus_type;
> > +
> > +struct vchiq_device *
> > +vchiq_device_register(struct device *parent, const char *name);
> > +void vchiq_device_unregister(struct vchiq_device *dev);
> > +
> > +int vchiq_driver_register(struct vchiq_driver *vchiq_drv);
> > +void vchiq_driver_unregister(struct vchiq_driver *vchiq_drv);
> > +
> > +/**
> > + * module_vchiq_driver() - Helper macro for registering a vchiq driver
> > + * @__vchiq_driver: vchiq driver struct
> > + *
> > + * Helper macro for vchiq drivers which do not do anything special in
> > + * module init/exit. This eliminates a lot of boilerplate. Each 
> > module may only
> > + * use this macro once, and calling it replaces module_init() and 
> > module_exit()
> > + */
> > +#define module_vchiq_driver(__vchiq_driver) \
> > +    module_driver(__vchiq_driver, vchiq_driver_register, 
> > vchiq_driver_unregister)
> > +
> > +#endif /* _VCHIQ_DEVICE_H */