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

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Message-ID: <62644cd8-c871-aee0-30b7-2fbab097504c@ideasonboard.com>
Date:   Mon, 23 Jan 2023 13:18:30 +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,

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);

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?