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From c3fc29179a4dbbd9efa90fb462ef5aac7507ec1a Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Thu, 1 Aug 2019 08:58:48 +0100
Subject: [PATCH 726/782] can: mcp251x: Allow more time after a reset
Some boards take longer than 5ms to power up after a reset, so allow
a few retry attempts before giving up.
See: https://github.com/raspberrypi/linux/issues/2767
Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
drivers/net/can/spi/mcp251x.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
--- a/drivers/net/can/spi/mcp251x.c
+++ b/drivers/net/can/spi/mcp251x.c
@@ -628,6 +628,7 @@ static int mcp251x_hw_reset(struct spi_d
struct mcp251x_priv *priv = spi_get_drvdata(spi);
u8 reg;
int ret;
+ int retries = 10;
/* Wait for oscillator startup timer after power up */
mdelay(MCP251X_OST_DELAY_MS);
@@ -637,10 +638,18 @@ static int mcp251x_hw_reset(struct spi_d
if (ret)
return ret;
- /* Wait for oscillator startup timer after reset */
- mdelay(MCP251X_OST_DELAY_MS);
+ /*
+ * Wait for oscillator startup timer after reset
+ *
+ * Some devices can take longer than the expected 5ms to wake
+ * up, so allow a few retries.
+ */
+
+ do {
+ mdelay(MCP251X_OST_DELAY_MS);
+ reg = mcp251x_read_reg(spi, CANSTAT);
+ } while (!reg && retries--);
- reg = mcp251x_read_reg(spi, CANSTAT);
if ((reg & CANCTRL_REQOP_MASK) != CANCTRL_REQOP_CONF)
return -ENODEV;
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