Re: [PATCH v6] amba: Remove deferred device addition

From: Isaac Manjarres
Date: Mon Aug 15 2022 - 15:33:31 EST


On Fri, Aug 12, 2022 at 08:30:46AM -0700, Guenter Roeck wrote:
> After more testing: the changes above result in qemu sx1 boot failures.
> There is no crash, boot just hangs.
>
> qemu command line:
>
> qemu-system-arm -M sx1 -kernel arch/arm/boot/zImage -no-reboot \
> -initrd rootfs-armv4.cpio \
> --append "rdinit=/sbin/init console=ttyS0,115200 earlycon=uart8250,mmio32,0xfffb0000,115200n8" \
> -nographic -monitor null -serial stdio
>
> with configuration from
> https://github.com/groeck/linux-build-test/blob/master/rootfs/arm/qemu_sx1_defconfig
> and root file system from
> https://github.com/groeck/linux-build-test/blob/master/rootfs/arm/rootfs-armv4.cpio.gz
>
> This is with your other patch applied.
>
> Guenter

Thanks for testing out the patch and sharing the qemu commandline you
used for the new issue. I was able to reproduce it on my end :) Can you
please try the following patch instead of the second patch I gave you?
This worked for me on sx1 and versatileab:

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index 32b0e0b930c1..110a535648d2 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -209,6 +209,7 @@ static int amba_match(struct device *dev, struct device_driver *drv)
struct amba_device *pcdev = to_amba_device(dev);
struct amba_driver *pcdrv = to_amba_driver(drv);

+ mutex_lock(&pcdev->periphid_lock);
if (!pcdev->periphid) {
int ret = amba_read_periphid(pcdev);

@@ -218,11 +219,14 @@ static int amba_match(struct device *dev, struct device_driver *drv)
* permanent failure in reading pid and cid, simply map it to
* -EPROBE_DEFER.
*/
- if (ret)
+ if (ret) {
+ mutex_unlock(&pcdev->periphid_lock);
return -EPROBE_DEFER;
+ }
dev_set_uevent_suppress(dev, false);
kobject_uevent(&dev->kobj, KOBJ_ADD);
}
+ mutex_unlock(&pcdev->periphid_lock);

/* When driver_override is set, only bind to the matching driver */
if (pcdev->driver_override)
@@ -532,6 +536,7 @@ static void amba_device_release(struct device *dev)

if (d->res.parent)
release_resource(&d->res);
+ mutex_destroy(&d->periphid_lock);
kfree(d);
}

@@ -584,6 +589,7 @@ static void amba_device_initialize(struct amba_device *dev, const char *name)
dev->dev.dma_mask = &dev->dev.coherent_dma_mask;
dev->dev.dma_parms = &dev->dma_parms;
dev->res.name = dev_name(&dev->dev);
+ mutex_init(&dev->periphid_lock);
}

/**
diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h
index e94cdf235f1d..5001e14c5c06 100644
--- a/include/linux/amba/bus.h
+++ b/include/linux/amba/bus.h
@@ -67,6 +67,7 @@ struct amba_device {
struct clk *pclk;
struct device_dma_parameters dma_parms;
unsigned int periphid;
+ struct mutex periphid_lock;
unsigned int cid;
struct amba_cs_uci_id uci;
unsigned int irq[AMBA_NR_IRQS];


Thanks,
Isaac