linux-kernel - Re: Grafting old platform drivers onto a new DT kernel

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Date:	Mon, 9 Nov 2015 16:15:03 +0100
From:	Mason <slash.tmp@...e.fr>
To:	Javier Martinez Canillas <javier@...hile0.org>,
	Andrew Lunn <andrew@...n.ch>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linux ARM <linux-arm-kernel@...ts.infradead.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Jason Cooper <jason@...edaemon.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: Grafting old platform drivers onto a new DT kernel

On 05/11/2015 16:42, Javier Martinez Canillas wrote:
> Hello,
> 
> On Thu, Nov 5, 2015 at 12:15 PM, Andrew Lunn <andrew@...n.ch> 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.

Hello,

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:
.reset
.set_clock
.set_bus_width
.set_uhs_signaling

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 
            CPU0       CPU1       
 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[] = {
	{
		.start	= TANGOX_SDIO0_BASE_ADDR,
		.end	= TANGOX_SDIO0_BASE_ADDR + 0x1ff,
		.flags	= IORESOURCE_MEM,
	},
	{
		.start	= 60,	/* SDHCI0 IRQ */
		.flags	= IORESOURCE_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?
https://www.kernel.org/doc/Documentation/IRQ-domain.txt

Should I use irq_linear_revmap() / irq_find_mapping() ?

Regards.

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