[RFC PATCH] remoteproc: imx_dsp_rproc: Fix multiple start/stop commands

[Rob Herring]

On Tue, Dec 09, 2025 at 04:04:25PM +0200, Daniel Baluta wrote:
> After commit 67a7bc7f0358 ("remoteproc: Use of reserved_mem_region_*
> functions for "memory-region"") following commands with
> imx-dsp-rproc started to fail:
>
> $ echo zephyr.elf > /sys/class/remoteproc/remoteproc0/firmware
> $ echo start > /sys/class/remoteproc/remoteproc0/state
> $ echo stop > /sys/class/remoteproc/remoteproc0/state
> $ echo start > /sys/class/remoteproc/remoteproc0/state #! This fails
> -sh: echo: write error: Device or resource busy

So unlike Marek's case, the first time works. Can you confirm your 
region is fixed address?

> This happens because aforementioned commit replaced devm_ioremap_wc with
> devm_ioremap_resource_wc which will "reserve" the memory region with the
> first start and then will fail at the second start if the memory
> region is already reserved.
> 
> So prefer using devm_ioremap_wc as there is no easy way to undo
> devm_iormep_resource_wc manually.
> 
> Fixes: 67a7bc7f0358 ("remoteproc: Use of_reserved_mem_region_* functions for "memory-region"")
> Signed-off-by: Daniel Baluta <daniel.baluta at nxp.com>
> ---
>  drivers/remoteproc/imx_dsp_rproc.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/remoteproc/imx_dsp_rproc.c b/drivers/remoteproc/imx_dsp_rproc.c
> index 5130a35214c9..79d5c15319f3 100644
> --- a/drivers/remoteproc/imx_dsp_rproc.c
> +++ b/drivers/remoteproc/imx_dsp_rproc.c
> @@ -709,10 +709,10 @@ static int imx_dsp_rproc_add_carveout(struct imx_dsp_rproc *priv)
>  		if (imx_dsp_rproc_sys_to_da(priv, res.start, resource_size(&res), &da))
>  			return -EINVAL;
>  
> -		cpu_addr = devm_ioremap_resource_wc(dev, &res);
> -		if (IS_ERR(cpu_addr)) {
> +		cpu_addr = devm_ioremap_wc(dev, res.start, resource_size(&res));

Best case this is reusing the same mapping and we just have unnecessary 
ioremap and iounmap calls and devm entries. Worst case, we get a new 
virtual mapping every time. IIRC, arm32 will reuse existing mapping, but 
arm64 does not. But that's 10+ years ago I looked into it.

Seems like devres is not the right lifetime. This should be just 
ioremap_wc() instead.

Rob