From a8298a009ad1698661f14d6ec771b5ea079439a9 Mon Sep 17 00:00:00 2001 From: Alexander Monakov Date: Sat, 28 Apr 2018 16:56:06 +0300 Subject: [PATCH] i2c: designware: fix poll-after-enable regression BugLink: http://bugs.launchpad.net/bugs/1782846 commit 06cb616b1bca7080824acfedb3d4c898e7a64836 upstream. Not all revisions of DW I2C controller implement the enable status register. On platforms where that's the case (e.g. BG2CD and SPEAr ARM SoCs), waiting for enable will time out as reading the unimplemented register yields zero. It was observed that reading the IC_ENABLE_STATUS register once suffices to avoid getting it stuck on Bay Trail hardware, so replace polling with one dummy read of the register. Fixes: fba4adbbf670 ("i2c: designware: must wait for enable") Signed-off-by: Alexander Monakov Tested-by: Ben Gardner Acked-by: Jarkko Nikula Signed-off-by: Wolfram Sang Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Kamal Mostafa Signed-off-by: Khalid Elmously --- drivers/i2c/busses/i2c-designware-master.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c index 13e849bf9aa0..4915fa303a7e 100644 --- a/drivers/i2c/busses/i2c-designware-master.c +++ b/drivers/i2c/busses/i2c-designware-master.c @@ -207,7 +207,10 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev) i2c_dw_disable_int(dev); /* Enable the adapter */ - __i2c_dw_enable_and_wait(dev, true); + __i2c_dw_enable(dev, true); + + /* Dummy read to avoid the register getting stuck on Bay Trail */ + dw_readl(dev, DW_IC_ENABLE_STATUS); /* Clear and enable interrupts */ dw_readl(dev, DW_IC_CLR_INTR); -- 2.39.5