Subject: [PATCH] powerpc/powermac: Use early_* IO variants in via_calibrate_decr

From: Benjamin Gray <[email-masked]>
Date: Thu, 6 Jul 2023 11:08:16 +1000

On a powermac platform, under the call path

  start_kernel
   time_init
    ppc_md.calibrate_decr (pmac_calibrate_decr)
     via_calibrate_decr

we run ioremap and iounmap. The unmap can enable interrupts
unexpectedly (cond_resched in vunmap_pmd_range), which is warned about
later in the boot sequence in start_kernel.

Use the early_* variants of these IO functions to prevent this.

The issue is pre-existing, but is surfaced by commit 721255b9826b
("genirq: Use a maple tree for interrupt descriptor management").
It's not clear to me why this causes it to surface.

Signed-off-by: Benjamin Gray <[email-masked]>
---
 arch/powerpc/platforms/powermac/time.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/powermac/time.c b/arch/powerpc/platforms/powermac/time.c
index 4c5790aff1b5..8633891b7aa5 100644
--- a/arch/powerpc/platforms/powermac/time.c
+++ b/arch/powerpc/platforms/powermac/time.c
@@ -26,8 +26,8 @@
 #include <linux/rtc.h>
 #include <linux/of_address.h>
 
+#include <asm/early_ioremap.h>
 #include <asm/sections.h>
-#include <asm/io.h>
 #include <asm/machdep.h>
 #include <asm/time.h>
 #include <asm/nvram.h>
@@ -182,7 +182,7 @@ static int __init via_calibrate_decr(void)
 		return 0;
 	}
 	of_node_put(vias);
-	via = ioremap(rsrc.start, resource_size(&rsrc));
+	via = early_ioremap(rsrc.start, resource_size(&rsrc));
 	if (via == NULL) {
 		printk(KERN_ERR "Failed to map VIA for timer calibration !\n");
 		return 0;
@@ -207,7 +207,7 @@ static int __init via_calibrate_decr(void)
 
 	ppc_tb_freq = (dstart - dend) * 100 / 6;
 
-	iounmap(via);
+	early_iounmap((void *)via, resource_size(&rsrc));
 
 	return 1;
 }
-- 
2.41.0