Re: [PATCH] dmaengine: bestcomm: ioremap early

[Rosen Penev]

On Mon, Aug 24, 2026 at 8:25 AM Frank Li <Frank.li@xxxxxxxxxxx> wrote:
>
> 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.
This section is generated from Sashiko. Same as the above.
>
> Frank
>
> >
> > Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>
> > ---
> >  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
> >