Hi Finn,
On Sat, Nov 21, 2020 at 12:47 AM Finn Thain fthain@telegraphics.com.au wrote:
On Fri, 20 Nov 2020, Geert Uytterhoeven wrote:
On Fri, Nov 20, 2020 at 5:51 AM Finn Thain fthain@telegraphics.com.au wrote:
Don't add platform resources that won't be used. This avoids a recently-added warning from the driver core, that can show up on a multi-platform kernel when !MACH_IS_MAC.
------------[ cut here ]------------ WARNING: CPU: 0 PID: 0 at drivers/base/platform.c:224 platform_get_irq_optional+0x8e/0xce 0 is an invalid IRQ number Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 5.9.0-multi #1 Stack from 004b3f04: 004b3f04 00462c2f 00462c2f 004b3f20 0002e128 004754db 004b6ad4 004b3f4c 0002e19c 004754f7 000000e0 00285ba0 00000009 00000000 004b3f44 ffffffff 004754db 004b3f64 004b3f74 00285ba0 004754f7 000000e0 00000009 004754db 004fdf0c 005269e2 004fdf0c 00000000 004b3f88 00285cae 004b6964 00000000 004fdf0c 004b3fac 0051cc68 004b6964 00000000 004b6964 00000200 00000000 0051cc3e 0023c18a 004b3fc0 0051cd8a 004fdf0c 00000002 0052b43c 004b3fc8 Call Trace: [<0002e128>] __warn+0xa6/0xd6 [<0002e19c>] warn_slowpath_fmt+0x44/0x76 [<00285ba0>] platform_get_irq_optional+0x8e/0xce [<00285ba0>] platform_get_irq_optional+0x8e/0xce [<00285cae>] platform_get_irq+0x12/0x4c [<0051cc68>] pmz_init_port+0x2a/0xa6 [<0051cc3e>] pmz_init_port+0x0/0xa6 [<0023c18a>] strlen+0x0/0x22 [<0051cd8a>] pmz_probe+0x34/0x88 [<0051cde6>] pmz_console_init+0x8/0x28 [<00511776>] console_init+0x1e/0x28 [<0005a3bc>] printk+0x0/0x16 [<0050a8a6>] start_kernel+0x368/0x4ce [<005094f8>] _sinittext+0x4f8/0xc48 random: get_random_bytes called from print_oops_end_marker+0x56/0x80 with crng_init=0 ---[ end trace 392d8e82eed68d6c ]---
Cc: Michael Ellerman mpe@ellerman.id.au Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: Paul Mackerras paulus@samba.org Cc: Joshua Thompson funaho@jurai.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Jiri Slaby jirislaby@kernel.org Cc: stable@vger.kernel.org # v5.8+ References: commit a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid") Reported-by: Laurent Vivier laurent@vivier.eu Signed-off-by: Finn Thain fthain@telegraphics.com.au
The global platform_device structs provide the equivalent of a direct search of the OpenFirmware tree, for platforms that don't have OF. The purpose of that search is discussed in the comments 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 backThe actual platform bus matching takes place later, with a module_initcall, following the usual pattern.
I think it would be good for this explanation to be part of the actual patch description above.
Thanks for your review.
I take that explanation as read because it was fundamental to the changes I made to pmac_zilog.c back in 2009 with commit ec9cbe09899e ("pmac-zilog: add platform driver").
That's a long time ago ;-) I asked because to the casual reader, it's far from obvious why the platform device use-time is different from the platform device's resources use-time.
IMO, being that it isn't news, it doesn't belong in the changelog. However, I agree that it needs to be documented. How about I add a comment to pmac_zilog.c?
Fine for me.
--- a/drivers/tty/serial/pmac_zilog.c +++ b/drivers/tty/serial/pmac_zilog.c @@ -1697,18 +1697,17 @@ extern struct platform_device scc_a_pdev, scc_b_pdev;
static int __init pmz_init_port(struct uart_pmac_port *uap) {
struct resource *r_ports;int irq;
struct resource *r_ports, *r_irq; r_ports = platform_get_resource(uap->pdev, IORESOURCE_MEM, 0);
irq = platform_get_irq(uap->pdev, 0);if (!r_ports || irq <= 0)
r_irq = platform_get_resource(uap->pdev, IORESOURCE_IRQ, 0);if (!r_ports || !r_irq) return -ENODEV; uap->port.mapbase = r_ports->start; uap->port.membase = (unsigned char __iomem *) r_ports->start; uap->port.iotype = UPIO_MEM;
uap->port.irq = irq;
uap->port.irq = r_irq->start; uap->port.uartclk = ZS_CLOCK; uap->port.fifosize = 1; uap->port.ops = &pmz_pops;Given the resources are no longer present on !MAC, just doing
r_ports = platform_get_resource(uap->pdev, IORESOURCE_MEM, 0); + if (!r_ports) + return -ENODEV; irq = platform_get_irq(uap->pdev, 0);should be sufficient?
I think your suggestion is shorter but not better. Commit a85a6c86c25b (which introduced the WARNING) suggests that testing for irq == 0 is undesirable. My patch resolves that.
As a bonus, by simply testing for the existence of both resources, I've addressed the mistake I made when I originally added the slick platform_get_irq() call instead of consistently using platform_get_resource().
platform_get_irq() hides a bunch of architecture-specific logic that is not appropriate here. The WARNING itself is a good example of that kind of logic.
Do you agree? If so, I will add this explanation to the commit log.
OK, your main motivation is to get rid of the zero-check. Leaving it could indeed trigger some janitorial changes by people who don't understand the code at all, so it's good to avoid that ;-)
Thanks!
Gr{oetje,eeting}s,
Geert