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

[Umang Jain]

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?