Re: [PATCH] powerpc/legacy_serial: Use early_ioremap()

On 24/03/20 10:54 am, Chris Packham wrote:

Hi Christophe,

On Wed, 2020-02-05 at 12:03 +0000, Christophe Leroy wrote:

quoted

[    0.000000] ioremap() called early from
find_legacy_serial_ports+0x3cc/0x474. Use early_ioremap() instead

I was just about to dig into this error message and found you patch. I
applied it to a v5.5 base.

quoted

find_legacy_serial_ports() is called early from setup_arch(), before
paging_init(). vmalloc is not available yet, ioremap shouldn't be
used that early.

Use early_ioremap() and switch to a regular ioremap() later.

Signed-off-by: Christophe Leroy <redacted>

On my system (Freescale T2080 SOC) this seems to cause a crash/hang in
early boot. Unfortunately because this is affecting the boot console I
don't get any earlyprintk output.

I've been doing a bit more digging into why Christophe's patch didn't 
work for me. I noticed the powerpc specific early_ioremap_range() 
returns addresses around ioremap_bot. Yet the generic early_ioremap() 
uses addresses around FIXADDR_TOP. If I try the following hack I can 
make Christophe's patch work

diff --git a/arch/powerpc/include/asm/fixmap.h 

b/arch/powerpc/include/asm/fixmap.h
index 2ef155a3c821..7bc2f3f73c8b 100644

--- a/arch/powerpc/include/asm/fixmap.h
+++ b/arch/powerpc/include/asm/fixmap.h

@@ -27,7 +27,7 @@
  #include <asm/kasan.h>
  #define FIXADDR_TOP    (KASAN_SHADOW_START - PAGE_SIZE)
  #else
-#define FIXADDR_TOP    ((unsigned long)(-PAGE_SIZE))
+#define FIXADDR_TOP    (IOREMAP_END - PAGE_SIZE)
  #endif

  /*

I'll admit to being out of my depth. It seems that the generic 
early_ioremap() is not quite correctly plumbed in for powerpc.

quoted

---
  arch/powerpc/kernel/legacy_serial.c | 33 +++++++++++++++++++++++++
----
  1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/legacy_serial.c

b/arch/powerpc/kernel/legacy_serial.c
index f061e06e9f51..8b2c1a8553a0 100644

--- a/arch/powerpc/kernel/legacy_serial.c
+++ b/arch/powerpc/kernel/legacy_serial.c

@@ -15,6 +15,7 @@
  #include <asm/udbg.h>
  #include <asm/pci-bridge.h>
  #include <asm/ppc-pci.h>
+#include <asm/early_ioremap.h>
  
  #undef DEBUG
  

@@ -34,6 +35,7 @@ static struct legacy_serial_info {
  	unsigned int			clock;
  	int				irq_check_parent;
  	phys_addr_t			taddr;
+	void __iomem			*early_addr;
  } legacy_serial_infos[MAX_LEGACY_SERIAL_PORTS];
  
  static const struct of_device_id legacy_serial_parents[] __initconst

= {

@@ -325,17 +327,16 @@ static void __init

setup_legacy_serial_console(int console)
  {
  	struct legacy_serial_info *info =
&legacy_serial_infos[console];
  	struct plat_serial8250_port *port =
&legacy_serial_ports[console];
-	void __iomem *addr;
  	unsigned int stride;
  
  	stride = 1 << port->regshift;
  
  	/* Check if a translated MMIO address has been found */
  	if (info->taddr) {
-		addr = ioremap(info->taddr, 0x1000);
-		if (addr == NULL)
+		info->early_addr = early_ioremap(info->taddr, 0x1000);
+		if (info->early_addr == NULL)
  			return;
-		udbg_uart_init_mmio(addr, stride);
+		udbg_uart_init_mmio(info->early_addr, stride);
  	} else {
  		/* Check if it's PIO and we support untranslated PIO */
  		if (port->iotype == UPIO_PORT && isa_io_special)

@@ -353,6 +354,30 @@ static void __init

setup_legacy_serial_console(int console)
  	udbg_uart_setup(info->speed, info->clock);
  }
  
+static int __init ioremap_legacy_serial_console(void)
+{
+	struct legacy_serial_info *info =
&legacy_serial_infos[legacy_serial_console];
+	struct plat_serial8250_port *port =
&legacy_serial_ports[legacy_serial_console];
+	void __iomem *vaddr;
+
+	if (legacy_serial_console < 0)
+		return 0;
+
+	if (!info->early_addr)
+		return 0;
+
+	vaddr = ioremap(info->taddr, 0x1000);
+	if (WARN_ON(!vaddr))
+		return -ENOMEM;
+
+	udbg_uart_init_mmio(vaddr, 1 << port->regshift);
+	early_iounmap(info->early_addr, 0x1000);
+	info->early_addr = NULL;
+
+	return 0;
+}
+early_initcall(ioremap_legacy_serial_console);
+
  /*
   * This is called very early, as part of setup_system() or
eventually
   * setup_arch(), basically before anything else in this file. This
function