linux-kernel - Re: [PATCH v6 0/6] staging: vc04_services: vchiq: Register devices with a custom bus

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Date:   Mon, 23 Jan 2023 19:42:01 +0530
From:   Umang Jain <umang.jain@...asonboard.com>
To:     Stefan Wahren <stefan.wahren@...e.com>,
        linux-staging@...ts.linux.dev,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Adrien Thierry <athierry@...hat.com>,
        Dan Carpenter <error27@...il.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Paul Elder <paul.elder@...asonboard.com>
Subject: Re: [PATCH v6 0/6] staging: vc04_services: vchiq: Register devices
 with a custom bus_type

Hi Stefan

On 1/23/23 5:16 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)
>
> just to avoid misunderstandings, did you read 
> drivers/staging/vc04_services/interface/TESTING ?

Yes, but it's not geared towards the hardware I have (Rpi Model 4B)
>
> The Raspberry Pi 4 is currently not fully supported for VCHIQ in 
> mainline. From my limited understanding the DMA controller driver 
> needs 40 bit support, so VCHIQ on BCM2711 can use it. This part is 
> currently only available in the vendor tree. The reason why the driver 
> is unexpectedly probing is a historical issue in the devicetree :-(
>
> Raspberry Pi 4 support is not considered as necessary for moving out 
> of staging.
>

While I am looking into what's the reason behind the hunk, without which 
the devices cannot get registered... This is not related to the 40bit 
support for DMA. I remember that it worked without it during the 
bcm2835-isp development.

Are you implying that I should not use RPi Model 4B for testing ? 
Because that's the only RPi hardware I own.
>>
>> 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);
>>
>> 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?