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

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Message-ID: <912601ba-c60d-8d69-f061-62b854c5d9ce@i2se.com>
Date:   Mon, 23 Jan 2023 12:46:10 +0100
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Umang Jain <umang.jain@...asonboard.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 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 ?

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.

>
> 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?