linux-kernel - Re: [PATCH v2 2/2] powerpc/legacy_serial: Use early

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Message-ID: <cb216c3f-1d88-b440-a43b-3a3fd9762c03@alliedtelesis.co.nz>
Date:   Tue, 20 Apr 2021 21:15:57 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "Michael Ellerman" <mpe@...erman.id.au>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v2 2/2] powerpc/legacy_serial: Use early_ioremap()

Hi Christophe,

On 21/04/21 1:32 am, Christophe Leroy wrote:
> From: Christophe Leroy <christophe.leroy@....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@....fr>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---

I gave it a spin on my T2080RDB. The error message is gone and I still 
get console output.

Tested-by: Chris Packham <chris.packham@...iedtelesis.co.nz>

>   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