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Commit 895c53e1 authored by Alexander Monakov's avatar Alexander Monakov Committed by Greg Kroah-Hartman
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i2c: designware: fix poll-after-enable regression 



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: default avatarAlexander Monakov <amonakov@ispras.ru>
Tested-by: default avatarBen Gardner <gardner.ben@gmail.com>
Acked-by: default avatarJarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f32bb2aa

drivers/i2c/busses/i2c-designware-core.c

+4 −1
Original line number Diff line number Diff line
@@ -507,7 +507,10 @@ 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);