Re: [PATCH v7 2/2] remoteproc: qcom: Use of_reserved_mem_region_* functions for "memory-region"

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hi Rob,

On 24.11.2025 19:27, Rob Herring (Arm) wrote:
> Use the newly added of_reserved_mem_region_to_resource() and
> of_reserved_mem_region_count() functions to handle "memory-region"
> properties.
>
> The error handling is a bit different in some cases. Often
> "memory-region" is optional, so failed lookup is not an error. But then
> an error in of_reserved_mem_lookup() is treated as an error. However,
> that distinction is not really important. Either the region is available
> and usable or it is not. So now, it is just
> of_reserved_mem_region_to_resource() which is checked for an error.
>
> Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

This patch landed in today's linux-next as commit c70b9d5fdcd7 
("remoteproc: qcom: Use of_reserved_mem_region_* functions for 
"memory-region""). In my tests I found that it breaks booting of 
DragonBoard410c (arch/arm64/boot/dts/qcom/apq8016-sbc.dts) by causing 
the NULL pointer dereference. The issue is caused by replacing 
devm_ioremap_wc() with devm_ioremap_resource_wc(), which fails on 
devm_request_mem_region(), see comment in the code below. It looks that 
the error handling is somewhere broken. Here is the the kernel log:

remoteproc remoteproc0: 4080000.remoteproc is available
qcom-wcnss-pil a204000.remoteproc: error -EBUSY: can't request region 
for resource [mem 0x8e200000-0x8e7fffff]
remoteproc remoteproc1: a204000.remoteproc is available
remoteproc remoteproc1: powering up a204000.remoteproc
remoteproc remoteproc1: Booting fw image qcom/apq8016/wcnss.mbn, size 
4111376
Unable to handle kernel paging request at virtual address fffffffffffffff0
Mem abort info:
...
Internal error: Oops: 0000000096000046 [#1]  SMP
Modules linked in: cpufreq_powersave qcom_wcnss_pil cpufreq_conservative 
coresight_stm coresight_replicator coresight_tmc coresight_tpiu stm_core 
coresight_funnel coresight_cpu_debug coresight_cti(+) adv7511 coresight 
nfc rfkill msm snd_soc_lpass_apq8016 snd_soc_apq8016_sbc 
snd_soc_lpass_cpu snd_soc_msm8916_analog snd_soc_msm8916_digital 
snd_soc_qcom_common snd_soc_lpass_platform snd_soc_core qrtr ubwc_config 
snd_compress llcc_qcom snd_pcm_dmaengine qcom_q6v5_mss snd_pcm ocmem 
qcom_pil_info qcom_spmi_vadc qcom_camss drm_gpuvm qcom_pon rtc_pm8xxx 
qcom_q6v5 qcom_spmi_temp_alarm venus_core qcom_vadc_common snd_timer 
drm_exec qcom_sysmon snd qcom_common gpu_sched videobuf2_dma_sg 
v4l2_mem2mem qcom_glink_smem v4l2_fwnode soundcore drm_dp_aux_bus 
qmi_helpers mdt_loader v4l2_async videobuf2_memops videobuf2_v4l2 
videodev qnoc_msm8916 videobuf2_common qcom_rng drm_display_helper mc 
qcom_stats rpmsg_ctrl rpmsg_char display_connector ramoops socinfo 
rmtfs_mem reed_solomon ax88796b asix usbnet phy_qcom_usb_hs ipv6 libsha1
CPU: 2 UID: 0 PID: 28 Comm: kworker/2:0 Tainted: G W           
6.18.0-rc1+ #16209 PREEMPT
Tainted: [W]=WARN
lr : __qcom_mdt_load+0x210/0x304 [mdt_loader]
Call trace:
  __pi_memcpy_generic+0x128/0x22c (P)
  qcom_mdt_load+0x68/0x60c [mdt_loader]
  wcnss_load+0x2c/0x5c [qcom_wcnss_pil]
  rproc_start+0x30/0x1b4
  rproc_boot+0x19c/0x560
  rproc_auto_boot_callback+0x1c/0x34
  request_firmware_work_func+0x4c/0x98
  process_one_work+0x208/0x60c
  worker_thread+0x244/0x388
  kthread+0x150/0x228
  ret_from_fork+0x10/0x20
Code: 927cec03 cb0e0021 8b0e0042 a9411c26 (a900340c)
---[ end trace 0000000000000000 ]---


> ---
> v7:
>   - Split QCom to separate patch
> ---
>   drivers/remoteproc/qcom_q6v5_adsp.c | 24 ++++------
>   drivers/remoteproc/qcom_q6v5_mss.c  | 60 ++++++++-----------------
>   drivers/remoteproc/qcom_q6v5_pas.c  | 69 +++++++++++------------------
>   drivers/remoteproc/qcom_q6v5_wcss.c | 25 +++++------
>   drivers/remoteproc/qcom_wcnss.c     | 23 ++++------
>   5 files changed, 72 insertions(+), 129 deletions(-)
>

> ...

> diff --git a/drivers/remoteproc/qcom_wcnss.c b/drivers/remoteproc/qcom_wcnss.c
> index 2c7e519a2254..14005fb049a2 100644
> --- a/drivers/remoteproc/qcom_wcnss.c
> +++ b/drivers/remoteproc/qcom_wcnss.c
> @@ -526,25 +526,20 @@ static int wcnss_request_irq(struct qcom_wcnss *wcnss,
>   
>   static int wcnss_alloc_memory_region(struct qcom_wcnss *wcnss)
>   {
> -	struct reserved_mem *rmem = NULL;
> -	struct device_node *node;
> -
> -	node = of_parse_phandle(wcnss->dev->of_node, "memory-region", 0);
> -	if (node)
> -		rmem = of_reserved_mem_lookup(node);
> -	of_node_put(node);
> +	struct resource res;
> +	int ret;
>   
> -	if (!rmem) {
> +	ret = of_reserved_mem_region_to_resource(wcnss->dev->of_node, 0, &res);
> +	if (ret) {
>   		dev_err(wcnss->dev, "unable to resolve memory-region\n");
> -		return -EINVAL;
> +		return ret;
>   	}
>   
> -	wcnss->mem_phys = wcnss->mem_reloc = rmem->base;
> -	wcnss->mem_size = rmem->size;
> -	wcnss->mem_region = devm_ioremap_wc(wcnss->dev, wcnss->mem_phys, wcnss->mem_size);
> +	wcnss->mem_phys = wcnss->mem_reloc = res.start;
> +	wcnss->mem_size = resource_size(&res);
> +	wcnss->mem_region = devm_ioremap_resource_wc(wcnss->dev, &res);

The above line causes the failure. After restoring it to:

wcnss->mem_region = devm_ioremap_wc(wcnss->dev, wcnss->mem_phys, wcnss->mem_size);

the mentioned board boots fine again. I'm not sure about other drivers, 
if they also fail the same way as they might not be used on the tested 
board.

>   	if (!wcnss->mem_region) {
> -		dev_err(wcnss->dev, "unable to map memory region: %pa+%zx\n",
> -			&rmem->base, wcnss->mem_size);
> +		dev_err(wcnss->dev, "unable to map memory region: %pR\n", &res);
>   		return -EBUSY;
>   	}
>   

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland