Re: [PATCH v6 0/6] staging: vc04_services: vchiq: Register devices with a custom bus_type

[Umang Jain <umang.jain@ideasonboard.com>]

Hi Stefan

On 1/23/23 10:58 PM, Stefan Wahren wrote:
> Hi Umang,
>
> Am 23.01.23 um 08:48 schrieb Umang Jain:
>> Hi Stefan,
>>
>> Thank for the testing.
>>
>> On 1/23/23 5:04 AM, Stefan Wahren wrote:
>>> Hi Umang,
>>>
>>> Am 20.01.23 um 21:10 schrieb Umang Jain:
>>>> This series just introduces five extra patches for dropping include
>>>> directives from Makefiles (suggested by Greg KH) and rebased.
>>>>
>>>> The main patch (6/6) removes platform device/driver abuse and moves
>>>> things to standard device/driver model using a custom_bus. Specific
>>>> details are elaborated in the commit message.
>>>>
>>>> The patch series is based on top of d514392f17fd (tag: next-20230120)
>>>> of linux-next.
>>>
>>> applied this series on top of linux-next and build it with 
>>> arm/multi_v7_defconfig plus the following:
>>>
>>> CONFIG_BCM_VIDEOCORE=y
>>> CONFIG_BCM2835_VCHIQ=m
>>> CONFIG_VCHIQ_CDEV=y
>>> CONFIG_SND_BCM2835=m
>>> CONFIG_VIDEO_BCM2835=m
>>> CONFIG_BCM2835_VCHIQ_MMAL=m
>>>
>>> and the devices doesn't register on Raspberry Pi 3 B Plus:
>>>
>>> [   25.523337] vchiq: module is from the staging directory, the 
>>> quality is unknown, you have been warned.
>>> [   25.541647] bcm2835_vchiq 3f00b840.mailbox: Failed to register 
>>> bcm2835_audio vchiq device
>>> [   25.553692] bcm2835_vchiq 3f00b840.mailbox: Failed to register 
>>> bcm2835-camera vchiq device
>>
>> I was able to reproduce and it seems the issue here is the change 
>> mentioned in the cover
>>
>> - drop dma_set_mask_and_coherent
>>
>> in V6.
>>
>> (I usually test patches on RPi 4B with vcsm-cma and bcm2835-isp 
>> applied so my branch has the DMA hunk included while I was testing V6)
>>
>> Below is the hunk which should resolve the issue.
>>
>> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
>> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
>> @@ -6,6 +6,7 @@
>>   */
>>
>>  #include <linux/device/bus.h>
>> +#include <linux/dma-mapping.h>
>>  #include <linux/slab.h>
>>  #include <linux/string.h>
>>
>> @@ -72,6 +73,12 @@ int vchiq_device_register(struct device *parent, 
>> const char *name)
>>         device->dev.type = &vchiq_device_type;
>>         device->dev.release = vchiq_device_release;
>>
>> +       ret = dma_set_mask_and_coherent(&device->dev, DMA_BIT_MASK(32));
>> +       if (ret < 0) {
>> +               vchiq_device_release(&device->dev);
>> +               return ret;
>> +       }
>> +
>>         ret = device_register(&device->dev);
>>         if (ret) {
>>                 put_device(&device->dev);
> Yes, this patch fixes the errors above. But i noticed that the series 
> also break autoprobing of bcm2835-audio and bcm2835-camera.

For the diff concerned, I am still looking into why is this needed.

Regarding the autoprobing, I have noticed that as well. It seems the 
probing is automatic for platform driver/devices and we are moving away 
from the platform driver/devices. So, this is expected I suppose?

Reading from Documentation/driver-api/driver-model/platform.rst

"""
Driver binding is performed automatically by the driver core, invoking 
driver probe() after finding a match between device and driver. If the 
probe() succeeds, the driver and device are bound as usual
"""

Should we retain this behavior ?
>>
>> It seems we need to include the dma_set_mask_and_coherent() even if 
>> bcm2835-audio, bcm2835-camera device doesn't do DMA? I need to look 
>> into why is that/
>>
>>  Laurent, any thoughts on this please?
>>
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