linux-kernel - Re: [PATCH 5.16 009/200] can: m_can: m_can_fifo_{read,write}: dont read or write from/to FIFO if length is 0

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Message-ID: <7da33ef9-67a4-343f-e97c-02d6bc40f2a9@photo-meter.com>
Date:   Mon, 14 Feb 2022 16:34:42 +0100
From:   Michael Anochin <anochin@...to-meter.com>
To:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5.16 009/200] can: m_can: m_can_fifo_{read,write}: dont
 read or write from/to FIFO if length is 0


There is no -22 error message now. Tested with "cansend can0 123#"

But now it floods continuous from __skb_queue_add_sort:

[ xxx.xxx] tcan4x5x spi0.0 can0: __skb_queue_add_sort: pos=0x000000, 
new=0x000000, diff= 0, queue_len=1

Only modprobe -r tcan4x5x or reboot helps


Hardware: RPI4 board with tcan4550 on spi0
Kernel 5.17.0-rc3-v7l+
from https://github.com/raspberrypi/linux/tree/rpi-5.17.y


Am 31.01.2022 um 11:54 schrieb Greg Kroah-Hartman:
> From: Marc Kleine-Budde <mkl@...gutronix.de>
> 
> commit db72589c49fd260bfc99c7160c079675bc7417af upstream.
> 
> In order to optimize FIFO access, especially on m_can cores attached
> to slow busses like SPI, in patch
> 
> | e39381770ec9 ("can: m_can: Disable IRQs on FIFO bus errors")
> 
> bulk read/write support has been added to the m_can_fifo_{read,write}
> functions.
> 
> That change leads to the tcan driver to call
> regmap_bulk_{read,write}() with a length of 0 (for CAN frames with 0
> data length). regmap treats this as an error:
> 
> | tcan4x5x spi1.0 tcan4x5x0: FIFO write returned -22
> 
> This patch fixes the problem by not calling the
> cdev->ops->{read,write)_fifo() in case of a 0 length read/write.
> 
> Fixes: e39381770ec9 ("can: m_can: Disable IRQs on FIFO bus errors")
> Link: https://lore.kernel.org/all/20220114155751.2651888-1-mkl@pengutronix.de
> Cc: stable@...r.kernel.org
> Cc: Matt Kline <matt@...bashing.io>
> Cc: Chandrasekar Ramakrishnan <rcsekar@...sung.com>
> Reported-by: Michael Anochin <anochin@...to-meter.com>
> Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>   drivers/net/can/m_can/m_can.c |    6 ++++++
>   1 file changed, 6 insertions(+)
> 
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -336,6 +336,9 @@ m_can_fifo_read(struct m_can_classdev *c
>   	u32 addr_offset = cdev->mcfg[MRAM_RXF0].off + fgi * RXF0_ELEMENT_SIZE +
>   		offset;
>   
> +	if (val_count == 0)
> +		return 0;
> +
>   	return cdev->ops->read_fifo(cdev, addr_offset, val, val_count);
>   }
>   
> @@ -346,6 +349,9 @@ m_can_fifo_write(struct m_can_classdev *
>   	u32 addr_offset = cdev->mcfg[MRAM_TXB].off + fpi * TXB_ELEMENT_SIZE +
>   		offset;
>   
> +	if (val_count == 0)
> +		return 0;
> +
>   	return cdev->ops->write_fifo(cdev, addr_offset, val, val_count);
>   }
>   
>