MCP251xFD runs interrupt handler twice per message.

* MCP251xFD runs interrupt handler twice per message.
@ 2022-01-14 11:05 Markus Mirevik
  2022-01-14 12:41 ` Marc Kleine-Budde
  0 siblings, 1 reply; 11+ messages in thread
From: Markus Mirevik @ 2022-01-14 11:05 UTC (permalink / raw)
  To: linux-can

Hello

I have performance problems with mcp2518fd. I have custom board based of beagleboard black. (Sitara am335x) using two mcp2518fd. The can communication uses a lot of CPU.  irq/64-spi1.1 uses around  ~20% at 1000 can messages/s.

I have several questions but I'll start with the most confusing.  I have found that every can messages fires two interrupts on my board. I have tested this in several ways. If I send one normal can message the counter in /proc/interrupts is increased twice. I have also put some printouts in mcp251xfd-core.c that confirms that mcp251xfd_irq() is run twice and the second time intf_pending is 0.

And for testing purposes I changed the interrupt config to trigger on falling edge instead of level and with this configured there is only one interrupt fired. But I guess this will risk locking the interrupt line low if an edge isn't detected. 

I have tried both with rx-int active and inactive. My scope shows really nice signals and that  rx-int and int is deactivated simultaneous on incoming frames. 

I'm testing by sending messages from my computer through a can dongle. 

The board is currently running Linux 5.10.79-yocto-tiny #1 SMP Tue Nov 16 03:57:43 UTC 2021 armv7l armv7l armv7l GNU/Linux
I've also tested updating the driver to the one from https://github.com/marckleinebudde/linux.git from 2021-12-29 with the same result (IRQ handler run twice). 

I am profoundly confused by this issue and I can not figure out why it's happening. My understanding is that since the IRQ handler is loaded with IRQF_ONESHOT the irq line should be masked until mcp251xfd_irq() returns. Since mcp251xfd_irq() checks that !rx_pending before exiting the int signal must be high. And the interrupt should not fire again... 

Result from init:
[    4.003029] mcp251xfd spi1.0 can0: MCP2518FD rev0.0 (+RX_INT -MAB_NO_WARN +CRC_REG +CRC_RX +CRC_TX +ECC -HD c:40.00MHz m:20.00MHz r:17.00MHz e:0.00MHz) successfully initialized.
[    4.028220] mcp251xfd spi1.1 can1: MCP2518FD rev0.0 (-RX_INT -MAB_NO_WARN +CRC_REG +CRC_RX +CRC_TX +ECC -HD c:40.00MHz m:20.00MHz r:17.00MHz e:0.00MHz) successfully initialized.

This is the current dtsi part for the canFD chips. (With rx-pin removed on one of the devices and trigger on edge on the other for debugging purposes). 

#include <dt-bindings/gpio/gpio.h>
#include <dt-bindings/interrupt-controller/irq.h>

&am33xx_pinmux{
        pinctrl_spi1_pins: pinctrl_spi1_pins {
                pinctrl-single,pins = <
                        AM33XX_IOPAD(0x990, PIN_INPUT | MUX_MODE3) /* (A13) mcasp0_aclkx.spi1_sclk */
                        AM33XX_IOPAD(0x994, PIN_INPUT | MUX_MODE3) /* (B13) mcasp0_fsx.spi1_d0 */
                        AM33XX_IOPAD(0x998, PIN_INPUT | MUX_MODE3) /* (D12) mcasp0_axr0.spi1_d1 */
                        AM33XX_IOPAD(0x96c, PIN_OUTPUT_PULLUP | MUX_MODE5) /* (E17) uart0_rtsn.spi1_cs0         CleANopen       LEFT*/
                        AM33XX_IOPAD(0x9b0, PIN_OUTPUT_PULLUP | MUX_MODE4) /* (A15) xdma_event_intr0.spi1_cs1   SAWM CAN        RIGHT*/
                >;
        };

        can0_int_pins: can0_int_pins {
                pinctrl-single,pins = <
                /*CleANopen*/
                AM33XX_IOPAD(0x89c, PIN_INPUT_PULLUP | MUX_MODE7) /* (T6) gpmc_be0n_cle.gpio2[5]        nINT            */
                AM33XX_IOPAD(0x968, PIN_INPUT_PULLUP | MUX_MODE7) /* (E18) uart0_ctsn.gpio1[8]          nINT1           */
                >;
        };

        can1_int_pins: can1_int_pins {
                pinctrl-single,pins = <
                /*SAWM CAN*/
                AM33XX_IOPAD(0x820, PIN_INPUT_PULLUP | MUX_MODE7) /* (U10) gpmc_ad8.gpio0[22]           nINT            */
                AM33XX_IOPAD(0x8c8, PIN_INPUT_PULLUP | MUX_MODE7) /* (U3) lcd_data10.gpio2[16]  nINT1           */
                AM33XX_IOPAD(0x8cc, PIN_INPUT_PULLUP | MUX_MODE7) /* (U4) lcd_data11.gpio2[17]  nINT0 NOT USED  */
                >;
        };
};

/{
        /* external 40M oscillator of mcp2518fd on SPI1.0 */
        mcp2518fd_can0_osc: mcp2518fd_can0_osc {
                compatible = "fixed-clock";
                #clock-cells = <0>;
                clock-frequency = <40000000>;
        };
};

/{
        /* external 40M oscillator of mcp2518fd on SPI1.1 */
        mcp2518fd_can1_osc: mcp2518fd_can1_osc {
                compatible = "fixed-clock";
                #clock-cells = <0>;
                clock-frequency = <40000000>;
        };
};

/* the spi config of the can-controller itself binding everything together */
&spi1{
    #address-cells = <1>;
    #size-cells = <0>;

    status = "okay";
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_spi1_pins>;

    /*CleANopen*/
    can@0 {
        compatible = "microchip,mcp2518fd";
        reg = <0>;
        clocks = <&mcp2518fd_can0_osc>;
        pinctrl-names = "default";
        pinctrl-0 = <&can0_int_pins>;
        spi-max-frequency = <20000000>;
        interrupts-extended = <&gpio2 5 IRQ_TYPE_EDGE_FALLING>;
        microchip,rx-int-gpios = <&gpio1 8 GPIO_ACTIVE_LOW>;
    };

    can@1 {
        compatible = "microchip,mcp2518fd";
        reg = <1>;
        clocks = <&mcp2518fd_can1_osc>;
        pinctrl-names = "default";
        pinctrl-0 = <&can1_int_pins>;
        spi-max-frequency = <20000000>;
        interrupts-extended = <&gpio0 22 IRQ_TYPE_LEVEL_LOW>;
//        microchip,rx-int-gpios = <&gpio2 16 GPIO_ACTIVE_LOW>;
    };
};

BR
Markus Mirevik

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