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:

quoted

Hi Stefan,

Thank for the testing.

On 1/23/23 5:04 AM, Stefan Wahren wrote:

quoted

Hi Umang,

Am 20.01.23 um 21:10 schrieb Umang Jain:

quoted

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.

quoted

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?

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