Re: Grafting old platform drivers onto a new DT kernel

From: Mason
Date: Mon Nov 09 2015 - 10:15:20 EST

On 05/11/2015 16:42, Javier Martinez Canillas wrote:
> Hello,
> On Thu, Nov 5, 2015 at 12:15 PM, Andrew Lunn <andrew@xxxxxxx> wrote:
>>> Since I don't have time to rewrite the drivers at the moment, I'm wondering
>>> if it's possible to "graft" old drivers (they're using the platform API, no
>>> trace of DT support) onto my small base?
>> Platform drivers are still usable with DT systems. We used that fact
>> when converting platform based machines over to DT, one driver at a
>> time. Look in the git history for kirkwood devices. e.g. somewhere
>> around v3.7, arch/arm/mach-kirkwood. board-dt.c, and the various
>> board-*.c files, and the DT files in the usual place.
> OMAP did the same and still some boards use platform data and manually
> register platform devices from board code. Take a look to
> arch/arm/mach-omap2/pdata-quirks.c to see how that is being done.


I tried compiling an ancient SDHCI driver on a v4.2 system. It crashes
all over init because several host->ops functions are required, but the
old driver does not define them:

So I downgraded to an older v3.14 kernel, and that problem vanished.
But I am having a problem with the IRQ setup.

# cat /proc/interrupts
18: 93 0 irq0 1 Level serial
55: 2832 0 irq0 38 Level 26000.ethernet
60: 0 0 irq0 43 Edge mmc0
211: 319 2603 GIC 29 Edge twd

Ethernet is using IRQ 38, as specified in the DT.
mmc0 is supposed to use IRQ 60.

I see that the mmc0 has the index 60, so I must have messed up between
the real irq (hwirq?) and the index Linux uses internally (virq?)

static struct resource sdhci_resources[] = {
.end = TANGOX_SDIO0_BASE_ADDR + 0x1ff,
.start = 60, /* SDHCI0 IRQ */

Both ethernet and sdhci driver call platform_get_irq(pdev, 0);
but the eth driver is DT, so calls of_irq_get() while sdhci is
legacy, so calls platform_get_resource() -- IIUC.

How do I specify a "hwirq" instead of a "Linux index"? and where?

Is this relevant?

Should I use irq_linear_revmap() / irq_find_mapping() ?


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