Hello Alexander Shiyan, Alexander Shiyan wrote: > On Fri, Jan 25, 2019 at 01:01:46PM +0100, Andreas Henriksson wrote: [...] >> According to my personal testing I can make the probing reliable just by >> raising MCP251X_OST_DELAY_MS [1] to 30ms which seems to be the sweet >> spot for me. (25ms isn't enough, while 40ms as suggested in last comment >> in the raspberrypi issue doesn't seem to be needed either.) [...] > Re-examining the code, I do not see obvious errors. However, the problem > is probably the implementation of the mdelay() for the ARM platform. (Can you please clue me in on the arm specific mdelay? I can't find any arm-specific bits overriding the default mdelay define[1], and with MCP251X_OST_DELAY_MS set to 5 that should be directly equivalent to 'udelay(5000);' as MAX_UDELAY_MS is also 5. Right?) > Can you do the test by replacing the lines mdelay(MCP251X_OST_DELAY_MS) > by udelay(2000)? Yes, exactly 2000. I've tested this now but no improvement. The interfaces comes up on every other "rmmod mcp251x; sleep 1 ; modprobe mcp251x" just like with plain 4.20.0. Attaching patch of my changes just to verify I didn't misunderstand what you wanted me to test. (I noticed in https://www.kernel.org/doc/Documentation/timers/timers-howto.txt that mdelay is discuraged in favour of msleep, but I'm not sure I really understood what the correct approach is after reading that doc.) Regards, Andreas Henriksson [1]: https://elixir.bootlin.com/linux/latest/source/include/linux/delay.h#L43
>From e4bf7421ba4f159e1c9023d4a890c82f28fa3806 Mon Sep 17 00:00:00 2001 From: Andreas Henriksson <andreas.henriksson@xxxxxxxxx> Date: Mon, 28 Jan 2019 09:54:31 +0100 Subject: [PATCH] TEST: mcp251x: use udelay(2000) instead of mdelay(5) https://www.spinics.net/lists/linux-can/msg01050.html --- drivers/net/can/spi/mcp251x.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/net/can/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c index e90817608645..97b27a85fbd2 100644 --- a/drivers/net/can/spi/mcp251x.c +++ b/drivers/net/can/spi/mcp251x.c @@ -215,8 +215,6 @@ #define TX_ECHO_SKB_MAX 1 -#define MCP251X_OST_DELAY_MS (5) - #define DEVICE_NAME "mcp251x" static int mcp251x_enable_dma; /* Enable SPI DMA. Default: 0 (Off) */ @@ -630,7 +628,7 @@ static int mcp251x_hw_reset(struct spi_device *spi) int ret; /* Wait for oscillator startup timer after power up */ - mdelay(MCP251X_OST_DELAY_MS); + udelay(2000); priv->spi_tx_buf[0] = INSTRUCTION_RESET; ret = mcp251x_spi_trans(spi, 1); @@ -638,7 +636,7 @@ static int mcp251x_hw_reset(struct spi_device *spi) return ret; /* Wait for oscillator startup timer after reset */ - mdelay(MCP251X_OST_DELAY_MS); + udelay(2000); reg = mcp251x_read_reg(spi, CANSTAT); if ((reg & CANCTRL_REQOP_MASK) != CANCTRL_REQOP_CONF) -- 2.20.1
