Currently the IOMEM AHCI registers space is mapped by means of the
two functions invocation: platform_get_resource() is used to get the very
first memory resource and devm_ioremap_resource() is called to remap that
resource. Device-managed kernel API provides a handy wrapper to perform
the same in single function call: devm_platform_ioremap_resource().

While at it seeing many AHCI platform drivers rely on having the AHCI CSR
space marked with "ahci" name let's first try to find and remap the CSR
IO-mem with that name and only if it fails fallback to getting the very
first registers space platform resource.

Signed-off-by: Serge Semin <redacted>
Reviewed-by: Hannes Reinecke <hare@suse.de>

---

Changelog v2:
- Check whether there is "ahci" reg resource before using the
  devm_platform_ioremap_resource_byname() method in order to prevent a
  false error message printed in the log (@Damien)
- Slightly update the patch title due to the change above and to be more
  specific about what the platform device managed methods are utilized
  for.
---
 drivers/ata/libahci_platform.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
index 32495ae96567..1e9e825d6cc5 100644
--- a/drivers/ata/libahci_platform.c
+++ b/drivers/ata/libahci_platform.c

@@ -402,8 +402,14 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
 
 	devres_add(dev, hpriv);
 
-	hpriv->mmio = devm_ioremap_resource(dev,
-			      platform_get_resource(pdev, IORESOURCE_MEM, 0));
+	/*
+	 * If the DT provided an "ahci" named resource, use it. Otherwise,
+	 * fallback to using the default first resource for the device node.
+	 */
+	if (platform_get_resource_byname(pdev, IORESOURCE_MEM, "ahci"))
+		hpriv->mmio = devm_platform_ioremap_resource_byname(pdev, "ahci");
+	else
+		hpriv->mmio = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(hpriv->mmio)) {
 		rc = PTR_ERR(hpriv->mmio);
 		goto err_out;

-- 
2.37.2