Re: [PATCH] dmaengine: bestcomm: ioremap early

[Frank Li <Frank.li@oss.nxp.com>]

On Sat, Aug 22, 2026 at 09:49:00PM -0700, Rosen Penev wrote:

subject: dmaengine: bestcomm: use devm_platform_get_and_ioremap_resource() to simplify code


> Doing so allows handling potential -EPROBE_DEFER before any work gets
> done.
>
> Replace the open-coded resource lookup, request_mem_region, ioremap and
> the manual iounmap/release_mem_region cleanup in probe/remove with the
> managed devm_platform_get_and_ioremap_resource() helper. This removes the
> now-unused error-unmap/release paths and simplifies probing.
>
> This also fixes a resource size mismatch between allocating and freeing.
> From sashiko:
>
> >  	release_mem_region(res_bcom.start, sizeof(struct mpc52xx_sdma));
>
> This is a pre-existing issue, but does this mismatch in size during release
> cause a permanent resource leak?

%s/?/.

> The memory region is requested earlier in mpc52xx_bcom_probe() using the
> device tree node size:
>     if (!request_mem_region(res_bcom.start, resource_size(&res_bcom),
>                             DRIVER_NAME)) {
> However, the error path above attempts to release the region using a fixed
> compile-time size: sizeof(struct mpc52xx_sdma). Since __release_region()
> strictly verifies the boundaries of the requested resource, if these sizes
> differ, the check fails and the I/O memory region is never freed. Driver
> unbinding in mpc52xx_bcom_remove() also uses this same fixed size.

Needn't this paragraph, "devm_platform_get_and_ioremap_resource..." already
clear enough.

Frank

>
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  drivers/dma/bestcomm/bestcomm.c | 45 ++++++++-------------------------
>  1 file changed, 10 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/dma/bestcomm/bestcomm.c b/drivers/dma/bestcomm/bestcomm.c
> index 432b43520ddc..44ff4a42376b 100644
> --- a/drivers/dma/bestcomm/bestcomm.c
> +++ b/drivers/dma/bestcomm/bestcomm.c
> @@ -13,7 +13,6 @@
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
>  #include <linux/of.h>
> -#include <linux/of_address.h>
>  #include <linux/of_irq.h>
>  #include <linux/platform_device.h>
>  #include <asm/io.h>
> @@ -365,13 +364,19 @@ bcom_engine_cleanup(void)
>  static int mpc52xx_bcom_probe(struct platform_device *op)
>  {
>  	struct device_node *ofn_sram;
> -	struct resource res_bcom;
> +	struct resource *res_bcom;
> +	void __iomem *regs;
>
>  	int rv;
>
>  	/* Inform user we're ok so far */
>  	printk(KERN_INFO "DMA: MPC52xx BestComm driver\n");
>
> +	/* Get, reserve & map io */
> +	regs = devm_platform_get_and_ioremap_resource(op, 0, &res_bcom);
> +	if (IS_ERR(regs))
> +		return PTR_ERR(regs);
> +
>  	/* Get the bestcomm node */
>  	of_node_get(op->dev.of_node);
>
> @@ -402,35 +407,13 @@ static int mpc52xx_bcom_probe(struct platform_device *op)
>  	/* Save the node */
>  	bcom_eng->ofnode = op->dev.of_node;
>
> -	/* Get, reserve & map io */
> -	if (of_address_to_resource(op->dev.of_node, 0, &res_bcom)) {
> -		printk(KERN_ERR DRIVER_NAME ": "
> -			"Can't get resource\n");
> -		rv = -EINVAL;
> -		goto error_sramclean;
> -	}
> -
> -	if (!request_mem_region(res_bcom.start, resource_size(&res_bcom),
> -				DRIVER_NAME)) {
> -		printk(KERN_ERR DRIVER_NAME ": "
> -			"Can't request registers region\n");
> -		rv = -EBUSY;
> -		goto error_sramclean;
> -	}
> -
> -	bcom_eng->regs_base = res_bcom.start;
> -	bcom_eng->regs = ioremap(res_bcom.start, sizeof(struct mpc52xx_sdma));
> -	if (!bcom_eng->regs) {
> -		printk(KERN_ERR DRIVER_NAME ": "
> -			"Can't map registers\n");
> -		rv = -ENOMEM;
> -		goto error_release;
> -	}
> +	bcom_eng->regs = regs;
> +	bcom_eng->regs_base = res_bcom->start;
>
>  	/* Now, do the real init */
>  	rv = bcom_engine_init();
>  	if (rv)
> -		goto error_unmap;
> +		goto error_sramclean;
>
>  	/* Done ! */
>  	printk(KERN_INFO "DMA: MPC52xx BestComm engine @%08lx ok !\n",
> @@ -439,10 +422,6 @@ static int mpc52xx_bcom_probe(struct platform_device *op)
>  	return 0;
>
>  	/* Error path */
> -error_unmap:
> -	iounmap(bcom_eng->regs);
> -error_release:
> -	release_mem_region(res_bcom.start, sizeof(struct mpc52xx_sdma));
>  error_sramclean:
>  	kfree(bcom_eng);
>  	bcom_sram_cleanup();
> @@ -463,10 +442,6 @@ static void mpc52xx_bcom_remove(struct platform_device *op)
>  	/* Cleanup SRAM */
>  	bcom_sram_cleanup();
>
> -	/* Release regs */
> -	iounmap(bcom_eng->regs);
> -	release_mem_region(bcom_eng->regs_base, sizeof(struct mpc52xx_sdma));
> -
>  	/* Release the node */
>  	of_node_put(bcom_eng->ofnode);
>
> --
> 2.55.0
>