Re: [PATCH v2 2/2] powerpc/legacy_serial: Use early_ioremap()

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 20/04/2021 23:32, Christophe Leroy wrote:
> From: Christophe Leroy <christophe.leroy@c-s.fr>
> 
> [    0.000000] ioremap() called early from find_legacy_serial_ports+0x3cc/0x474. Use early_ioremap() instead
> 
> 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>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

My POWER9 box silently reboots with the upstream kernel which has this.

This hunk:

diff --git a/arch/powerpc/kernel/legacy_serial.c 
b/arch/powerpc/kernel/legacy_serial.c
index f061e06e9f51..6bdb3f5f64e3 100644
--- a/arch/powerpc/kernel/legacy_serial.c
+++ b/arch/powerpc/kernel/legacy_serial.c
@@ -336,6 +336,16 @@ static void __init setup_legacy_serial_console(int 
console)
                 if (addr == NULL)
                         return;
                 udbg_uart_init_mmio(addr, stride);
+
+
+               {
+                       void *ea = early_ioremap(info->taddr, 0x1000);
+                       pr_err("___K___ (%u) %s %u: ior=%lx early=%lx\n",
+                               smp_processor_id(), __func__, __LINE__,
+                                       (unsigned long) addr, (unsigned 
long) ea);
+                       early_iounmap(ea, 0x1000);
+               }
+


produced:

[    0.000000] ___K___ (0) setup_legacy_serial_console 345: 
ior=c00a0000800003f8 early=ffffffffffc003f8 



The early address just does not look right - ffffffffffc003f8. Do you 
have a quick idea what is exactly wrong before I wake up and dig more? 
:)  It is powernv_defconfig. Thanks,



> ---
>   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
> 

-- 
Alexey