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

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Date:   Wed, 21 Oct 2020 10:43:37 +1100 (AEDT)
From:   Finn Thain <fthain@...egraphics.com.au>
To:     Brad Boyer <brad@...andria.com>
cc:     Laurent Vivier <laurent@...ier.eu>,
        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

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;