From cd6fa8d2ca53cac3226fdcffcf763be390abae32 Mon Sep 17 00:00:00 2001 From: Alexander Sverdlin Date: Fri, 27 Feb 2015 16:30:21 +0100 Subject: [PATCH] spi: pl022: Fix race in giveback() leading to driver lock-up Commit fd316941c ("spi/pl022: disable port when unused") introduced a race, which leads to possible driver lock up (easily reproducible on SMP). The problem happens in giveback() function where the completion of the transfer is signalled to SPI subsystem and then the HW SPI controller is disabled. Another transfer might be setup in between, which brings driver in locked-up state. Exact event sequence on SMP: core0 core1 => pump_transfers() /* message->state == STATE_DONE */ => giveback() => spi_finalize_current_message() => pl022_unprepare_transfer_hardware() => pl022_transfer_one_message => flush() => do_interrupt_dma_transfer() => set_up_next_transfer() /* Enable SSP, turn on interrupts */ writew((readw(SSP_CR1(pl022->virtbase)) | SSP_CR1_MASK_SSE), SSP_CR1(pl022->virtbase)); ... => pl022_interrupt_handler() => readwriter() /* disable the SPI/SSP operation */ => writew((readw(SSP_CR1(pl022->virtbase)) & (~SSP_CR1_MASK_SSE)), SSP_CR1(pl022->virtbase)); Lockup! SPI controller is disabled and the data will never be received. Whole SPI subsystem is waiting for transfer ACK and blocked. So, only signal transfer completion after disabling the controller. Fixes: fd316941c (spi/pl022: disable port when unused) Signed-off-by: Alexander Sverdlin Signed-off-by: Mark Brown Cc: stable@vger.kernel.org --- drivers/spi/spi-pl022.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/spi/spi-pl022.c b/drivers/spi/spi-pl022.c index 89ca162801da..ee513a85296b 100644 --- a/drivers/spi/spi-pl022.c +++ b/drivers/spi/spi-pl022.c @@ -534,12 +534,12 @@ static void giveback(struct pl022 *pl022) pl022->cur_msg = NULL; pl022->cur_transfer = NULL; pl022->cur_chip = NULL; - spi_finalize_current_message(pl022->master); /* disable the SPI/SSP operation */ writew((readw(SSP_CR1(pl022->virtbase)) & (~SSP_CR1_MASK_SSE)), SSP_CR1(pl022->virtbase)); + spi_finalize_current_message(pl022->master); } /** -- 2.34.1