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

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Date:   Mon, 23 Mar 2020 21:54:01 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     "christophe.leroy@....fr" <christophe.leroy@....fr>,
        "paulus@...ba.org" <paulus@...ba.org>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>
CC:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Hamish Martin <Hamish.Martin@...iedtelesis.co.nz>
Subject: Re: [PATCH] powerpc/legacy_serial: Use early_ioremap()

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@....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.

> ---
>  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