linux-kernel - Re: [PATCH] serial: pmac_zilog: don't init if zilog is not available

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Message-ID: <311d17ed-75fa-a7fe-6c70-177a6eec4519@vivier.eu>
Date:   Wed, 21 Oct 2020 09:54:17 +0200
From:   Laurent Vivier <laurent@...ier.eu>
To:     Finn Thain <fthain@...egraphics.com.au>,
        Brad Boyer <brad@...andria.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, linux-kernel@...r.kernel.org,
        Joshua Thompson <funaho@...ai.org>,
        linux-serial@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linux-m68k@...ts.linux-m68k.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH] serial: pmac_zilog: don't init if zilog is not available

Le 21/10/2020 à 01:43, Finn Thain a écrit :
> On Tue, 20 Oct 2020, Brad Boyer wrote:
> 
>>
>> Wouldn't it be better to rearrange this code to only run if the devices 
>> are present? This is a macio driver on pmac and a platform driver on 
>> mac, so shouldn't it be possible to only run this code when the 
>> appropriate entries are present in the right data structures?
>>
>> I didn't look at a lot of the other serial drivers, but some other mac 
>> drivers have recently been updated to no longer have MACH_IS_MAC checks 
>> due to being converted to platform drivers.
>>
> 
> Actually, it's not simply a platform driver or macio driver. I think the 
> console is supposed to be registered before the normal bus matching takes 
> place. Hence this comment in pmac_zilog.c,
> 
>         /* 
>          * First, we need to do a direct OF-based probe pass. We
>          * do that because we want serial console up before the
>          * macio stuffs calls us back, and since that makes it
>          * easier to pass the proper number of channels to
>          * uart_register_driver()
>          */
> 
> Laurent, can we avoid the irq == 0 warning splat like this?
> 
> diff --git a/drivers/tty/serial/pmac_zilog.c b/drivers/tty/serial/pmac_zilog.c
> index 96e7aa479961..7db600cd8cc7 100644
> --- a/drivers/tty/serial/pmac_zilog.c
> +++ b/drivers/tty/serial/pmac_zilog.c
> @@ -1701,8 +1701,10 @@ static int __init pmz_init_port(struct uart_pmac_port *uap)
>  	int irq;
>  
>  	r_ports = platform_get_resource(uap->pdev, IORESOURCE_MEM, 0);
> +	if (!r_ports)
> +		return -ENODEV;
>  	irq = platform_get_irq(uap->pdev, 0);
> -	if (!r_ports || irq <= 0)
> +	if (irq <= 0)
>  		return -ENODEV;
>  
>  	uap->port.mapbase  = r_ports->start;
> 

No, this doesn't fix the problem.

The message is still:

[    0.000000] ------------[ cut here ]------------
[    0.000000] WARNING: CPU: 0 PID: 0 at drivers/base/platform.c:224
platform_get_irq_optional+0x7a/0x80
[    0.000000] 0 is an invalid IRQ number
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.9.0+ #324
[    0.000000] Stack from 004e7f24:
                       004e7f24 0046c1d3 0046c1d3 0002cb26 004985fb
000000e0 00000009 00000000
                       0002cb6a 004985fb 000000e0 002a5b86 00000009
00000000 004e7f70 00553cc4
                       00000000 00000000 00000000 004985df 004e7f90
004e7ff8 002a5b86 004985fb
                       000000e0 00000009 004985df 004eb290 002a5bd2
004eb290 00000000 00553cc4
                       0057bb66 00553cc4 00573d6e 004eb290 00000000
00573d38 0021c42c 00573e06
                       00553cc4 0046df15 00583a7c 00573e58 00564b74
0005299a 0055ce34 00000000
[    0.000000] Call Trace: [<0002cb26>] __warn+0xb2/0xb4
[    0.000000]  [<0002cb6a>] warn_slowpath_fmt+0x42/0x64
[    0.000000]  [<002a5b86>] platform_get_irq_optional+0x7a/0x80
[    0.000000]  [<002a5b86>] platform_get_irq_optional+0x7a/0x80
[    0.000000]  [<002a5bd2>] platform_get_irq+0x16/0x42
[    0.000000]  [<00573d6e>] pmz_init_port+0x36/0x9e
[    0.000000]  [<00573d38>] pmz_init_port+0x0/0x9e
[    0.000000]  [<0021c42c>] strlen+0x0/0x14
[    0.000000]  [<00573e06>] pmz_probe+0x30/0x7e
[    0.000000]  [<00573e58>] pmz_console_init+0x4/0x22
[    0.000000]  [<00564b74>] console_init+0x1e/0x20
[    0.000000]  [<0005299a>] printk+0x0/0x18
[    0.000000]  [<0055ce34>] start_kernel+0x332/0x4c4
[    0.000000]  [<0055b8c6>] _sinittext+0x8c6/0x1268
[    0.000000] ---[ end trace 32d780b8cd50b829 ]---

Thanks,
Laurent