IRQ's missing with MPC5200 GPT as an interrupt controller

[Grant Likely]

Hi Henk,

On Mon, Mar 8, 2010 at 8:20 AM, Henk Stegeman <henk.stegeman at gmail.com> wrote:
> I'm trying to make use of the GPT as interrupt controller.
> My driver is getting most, but not all of the interrupts, besides that
> I'm getting a whole bunch of spurious IRQs, so I'm trying to figure
> out what's wrong.
>
>                gpt6: timer at 660 {
>                        compatible = "fsl,mpc5200b-gpt","fsl,mpc5200-gpt";
>                        reg = <0x660 0x10>;
>                        interrupts = <1 15 0>;
>                        interrupt-controller;
>                        #interrupt-cells = <1>;
>                };
>
> My device has the interrupt-parent property which links it to the
> above interrupt controller.
>
>                spi at f00 {
>                        #address-cells = <1>;
>                        #size-cells = <0>;
>                        compatible = "fsl,mpc5200b-spi","fsl,mpc5200-spi";
>                        reg = <0xf00 0x20>;
>                        interrupts = <2 13 0 2 14 0>;
>
>                        io-controller at 0 {
>                                compatible = "microkey,smc4000io";
>                                linux,modalias = "of_smc4000io";
>                                spi-max-frequency = <800000>;
>                                spi-cpha;
>                                reg = <0>;
>                                word-delay-us = <30>;
>                                interrupt-parent = <&gpt6>;
>                                interrupts = <2>; // And make it edge falling
>                        };
>
> There are two things I find suspicious:
> - First of all my interrupt is listed as virq# 16, shouldn't it be
> virq# 0x50 ? (16 is te L2 value virq# 0x50 of mpc52xx_irqhost_map)

The GPT irq registered as a different IRQ controller, so it will be
assigned an entirely different number within the virq range.

> - Secondly in mpc52xx_gpt.c  mpc52xx_gpt_irq_mask() and
> mpc52xx_gpt_irq_unmask() resp. clear and set the IrqEn bit of the GPT,
> which is described in the MPC5200B_UM as "enables interrupt generation
> to the CPU for all modes". The word 'generation' makes me suspicious,
> because it could mean that while irqEn is cleared an edge on the GPT's
> input does not even request an IRQ immediately after the bit is
> cleared.  Or in other words, clearing the bit could do more that just
> masking.

Could be, the IRQ support has not gotten extensive testing.  It may
require additional work.

> ~ # cat /proc/interrupts
>           CPU0
>  16:    1338686   MPC52xx GPT      Edge         smc4000io
> 129:      83224   MPC52xx Peripherals Level        mpc52xx_psc_uart
> 130:          1   MPC52xx Peripherals Level        mpc52xx_psc_uart
> 133:          0   MPC52xx Peripherals Level        mpc52xx-fec_ctrl
> 134:          0   MPC52xx Peripherals Level        ohci_hcd:usb1
> 135:      16127   MPC52xx Peripherals Level        mpc52xx_ata
> 141:          0   MPC52xx Peripherals Level        mpc5200-spi-modf
> 142:      79184   MPC52xx Peripherals Level        mpc5200-spi-spif
> 192:          0   MPC52xx SDMA     Level        ATA task
> 193:         15   MPC52xx SDMA     Level        mpc52xx-fec_rx
> 194:      35615   MPC52xx SDMA     Level        mpc52xx-fec_tx
> LOC:     134286   Local timer interrupts
> SPU:     576958   Spurious interrupts
> CNT:          0   Performance monitoring interrupts
> MCE:          0   Machine check exceptions
>
> ~ # dmesg |grep 660
> [    1.975928] irq: irq 0 on host /soc5200 at f0000000/timer at 660 mapped
> to virtual irq 16
>
> ~ # dmesg | grep host_map
> [    0.000000] mpc52xx_irqhost_map: virq=81, l1=2, l2=1
> [    0.319272] mpc52xx_irqhost_map: External IRQ1 virq=41, hw=41. type=8
> [    0.376117] mpc52xx_irqhost_map: virq=49, l1=1, l2=9
> [    0.417213] mpc52xx_irqhost_map: virq=4a, l1=1, l2=10
> [    0.452119] mpc52xx_irqhost_map: virq=4b, l1=1, l2=11
> [    0.487031] mpc52xx_irqhost_map: virq=4c, l1=1, l2=12
> [    0.529899] mpc52xx_irqhost_map: virq=4d, l1=1, l2=13
> [    0.564821] mpc52xx_irqhost_map: virq=4e, l1=1, l2=14
> [    0.599744] mpc52xx_irqhost_map: virq=4f, l1=1, l2=15
> [    0.634669] mpc52xx_irqhost_map: virq=50, l1=1, l2=16
> [    1.629764] mpc52xx_irqhost_map: virq=82, l1=2, l2=2
> [    1.667194] mpc52xx_irqhost_map: virq=84, l1=2, l2=4
> [    1.763299] mpc52xx_irqhost_map: virq=87, l1=2, l2=7
> [    1.790510] mpc52xx_irqhost_map: virq=c0, l1=3, l2=0
> [    1.909341] mpc52xx_irqhost_map: virq=8d, l1=2, l2=13
> [    1.936712] mpc52xx_irqhost_map: virq=8e, l1=2, l2=14
> [    2.055579] mpc52xx_irqhost_map: virq=c1, l1=3, l2=1
> [    2.083018] mpc52xx_irqhost_map: virq=c2, l1=3, l2=2
> [    2.110345] mpc52xx_irqhost_map: virq=85, l1=2, l2=5
> [    2.211890] mpc52xx_irqhost_map: virq=86, l1=2, l2=6

This grep only shows the output from mpc52xx_intc.c.  The GPT driver
has its own IRQ mapping function; mpc52xx_gpt_irq_map(), which is why
you're not seeing your IRQ map debug message.

Cheers,
g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.