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SubjectRe: [PATCH] powerpc/legacy_serial: Use early_ioremap()
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On 24/03/20 10:54 am, Chris Packham wrote:
> Hi Christophe,
>
> On Wed, 2020-02-05 at 12:03 +0000, Christophe Leroy wrote:
>> [ 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.
>
>> 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 <christophe.leroy@c-s.fr>
> 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.

>> ---
>> 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
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