Memory resources are optional but if the resource is empty
devm_platform_get_and_ioremap_resource() prints an error nonetheless.
Refactor the code to check the resources locally first and process them
only if they are present. The -EBUSY error message of ioremap_resource()
is still kept because it is correct. The comment which explains that a
plain ioremap() is tried as a workaround is turned into a info message.
So, a user will be informed about it, too.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---

Changes since v3:
* fixed __iomem annotations (Thanks, sparse + buildbots)
* rebased to 7.0-rc2

 drivers/mailbox/mailbox-test.c | 37 +++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
index 3a28ab5c42e5..058c0fe4b9c2 100644
--- a/drivers/mailbox/mailbox-test.c
+++ b/drivers/mailbox/mailbox-test.c
@@ -355,11 +355,27 @@ mbox_test_request_channel(struct platform_device *pdev, const char *name)
 	return channel;
 }
 
+static void __iomem *mbox_test_ioremap(struct platform_device *pdev, unsigned int res_num)
+{
+	struct resource *res;
+	void __iomem *mmio;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, res_num);
+	if (!res)
+		return NULL;
+
+	mmio = devm_ioremap_resource(&pdev->dev, res);
+	if (PTR_ERR(mmio) == -EBUSY) {
+		dev_info(&pdev->dev, "trying workaround with plain ioremap\n");
+		return devm_ioremap(&pdev->dev, res->start, resource_size(res));
+	}
+
+	return IS_ERR(mmio) ? NULL : mmio;
+}
+
 static int mbox_test_probe(struct platform_device *pdev)
 {
 	struct mbox_test_device *tdev;
-	struct resource *res;
-	resource_size_t size;
 	int ret;
 
 	tdev = devm_kzalloc(&pdev->dev, sizeof(*tdev), GFP_KERNEL);
@@ -367,23 +383,12 @@ static int mbox_test_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	/* It's okay for MMIO to be NULL */
-	tdev->tx_mmio = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
-	if (PTR_ERR(tdev->tx_mmio) == -EBUSY) {
-		/* if reserved area in SRAM, try just ioremap */
-		size = resource_size(res);
-		tdev->tx_mmio = devm_ioremap(&pdev->dev, res->start, size);
-	} else if (IS_ERR(tdev->tx_mmio)) {
-		tdev->tx_mmio = NULL;
-	}
+	tdev->tx_mmio = mbox_test_ioremap(pdev, 0);
 
 	/* If specified, second reg entry is Rx MMIO */
-	tdev->rx_mmio = devm_platform_get_and_ioremap_resource(pdev, 1, &res);
-	if (PTR_ERR(tdev->rx_mmio) == -EBUSY) {
-		size = resource_size(res);
-		tdev->rx_mmio = devm_ioremap(&pdev->dev, res->start, size);
-	} else if (IS_ERR(tdev->rx_mmio)) {
+	tdev->rx_mmio = mbox_test_ioremap(pdev, 1);
+	if (!tdev->rx_mmio)
 		tdev->rx_mmio = tdev->tx_mmio;
-	}
 
 	tdev->tx_channel = mbox_test_request_channel(pdev, "tx");
 	tdev->rx_channel = mbox_test_request_channel(pdev, "rx");
-- 
2.47.3

On Mon, 9 Mar 2026 at 08:41, Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
> Memory resources are optional but if the resource is empty
> devm_platform_get_and_ioremap_resource() prints an error nonetheless.
> Refactor the code to check the resources locally first and process them
> only if they are present. The -EBUSY error message of ioremap_resource()
> is still kept because it is correct. The comment which explains that a
> plain ioremap() is tried as a workaround is turned into a info message.
> So, a user will be informed about it, too.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> ---
>
> Changes since v3:
> * fixed __iomem annotations (Thanks, sparse + buildbots)
> * rebased to 7.0-rc2

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds