Re: [PATCH] dmaengine: bestcomm: ioremap early

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

On Mon, Aug 24, 2026 at 01:24:06PM -0700, Rosen Penev wrote:
> On Mon, Aug 24, 2026 at 8:25 AM Frank Li <Frank.li@oss.nxp.com> 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.

AI provided more detail information to help us understand situation, but
sometime it is long-winded.  Git commit need a nice summary. This is
simple code cleanup.

Frank

> >
> > 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
> > >