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Subject[PATCH v3 06/12] spi: spi-fsl-dspi: Replace interruptible wait queue with a simple completion
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From: Vladimir Oltean <vladimir.oltean@nxp.com>

Currently the driver puts the process in interruptible sleep waiting for
the interrupt train to finish transfer to/from the tx_buf and rx_buf.

But exiting the process with ctrl-c may make the kernel panic: the
wait_event_interruptible call will return -ERESTARTSYS, which a proper
driver implementation is perhaps supposed to handle, but nonetheless
this one doesn't, and aborts the transfer altogether.

Actually when the task is interrupted, there is still a high chance that
the dspi_interrupt is still triggering. And if dspi_transfer_one_message
returns execution all the way to the spi_device driver, that can free
the spi_message and spi_transfer structures, leaving the interrupts to
access a freed tx_buf and rx_buf.

hexdump -C /dev/mtd0
00000000 00 75 68 75 0a ff ff ff ff ff ff ff ff ff ff ff
|.uhu............|
00000010 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
|................|
*
^C[ 38.495955] fsl-dspi 2120000.spi: Waiting for transfer to complete failed!
[ 38.503097] spi_master spi2: failed to transfer one message from queue
[ 38.509729] Unable to handle kernel paging request at virtual address ffff800095ab3377
[ 38.517676] Mem abort info:
[ 38.520474] ESR = 0x96000045
[ 38.523533] EC = 0x25: DABT (current EL), IL = 32 bits
[ 38.528861] SET = 0, FnV = 0
[ 38.531921] EA = 0, S1PTW = 0
[ 38.535067] Data abort info:
[ 38.537952] ISV = 0, ISS = 0x00000045
[ 38.541797] CM = 0, WnR = 1
[ 38.544771] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000082621000
[ 38.551494] [ffff800095ab3377] pgd=00000020fffff003, p4d=00000020fffff003, pud=0000000000000000
[ 38.560229] Internal error: Oops: 96000045 [#1] PREEMPT SMP
[ 38.565819] Modules linked in:
[ 38.568882] CPU: 0 PID: 2729 Comm: hexdump Not tainted 5.6.0-rc4-next-20200306-00052-gd8730cdc8a0b-dirty #193
[ 38.578834] Hardware name: Kontron SMARC-sAL28 (Single PHY) on SMARC Eval 2.0 carrier (DT)
[ 38.587129] pstate: 20000085 (nzCv daIf -PAN -UAO)
[ 38.591941] pc : ktime_get_real_ts64+0x3c/0x110
[ 38.596487] lr : spi_take_timestamp_pre+0x40/0x90
[ 38.601203] sp : ffff800010003d90
[ 38.604525] x29: ffff800010003d90 x28: ffff80001200e000
[ 38.609854] x27: ffff800011da9000 x26: ffff002079c40400
[ 38.615184] x25: ffff8000117fe018 x24: ffff800011daa1a0
[ 38.620513] x23: ffff800015ab3860 x22: ffff800095ab3377
[ 38.625841] x21: 000000000000146e x20: ffff8000120c3000
[ 38.631170] x19: ffff0020795f6e80 x18: ffff800011da9948
[ 38.636498] x17: 0000000000000000 x16: 0000000000000000
[ 38.641826] x15: ffff800095ab3377 x14: 0720072007200720
[ 38.647155] x13: 0720072007200765 x12: 0775076507750771
[ 38.652483] x11: 0720076d076f0772 x10: 0000000000000040
[ 38.657812] x9 : ffff8000108e2100 x8 : ffff800011dcabe8
[ 38.663139] x7 : 0000000000000000 x6 : ffff800015ab3a60
[ 38.668468] x5 : 0000000007200720 x4 : ffff800095ab3377
[ 38.673796] x3 : 0000000000000000 x2 : 0000000000000ab0
[ 38.679125] x1 : ffff800011daa000 x0 : 0000000000000026
[ 38.684454] Call trace:
[ 38.686905] ktime_get_real_ts64+0x3c/0x110
[ 38.691100] spi_take_timestamp_pre+0x40/0x90
[ 38.695470] dspi_fifo_write+0x58/0x2c0
[ 38.699315] dspi_interrupt+0xbc/0xd0
[ 38.702987] __handle_irq_event_percpu+0x78/0x2c0
[ 38.707706] handle_irq_event_percpu+0x3c/0x90
[ 38.712161] handle_irq_event+0x4c/0xd0
[ 38.716008] handle_fasteoi_irq+0xbc/0x170
[ 38.720115] generic_handle_irq+0x2c/0x40
[ 38.724135] __handle_domain_irq+0x68/0xc0
[ 38.728243] gic_handle_irq+0xc8/0x160
[ 38.732000] el1_irq+0xb8/0x180
[ 38.735149] spi_nor_spimem_read_data+0xe0/0x140
[ 38.739779] spi_nor_read+0xc4/0x120
[ 38.743364] mtd_read_oob+0xa8/0xc0
[ 38.746860] mtd_read+0x4c/0x80
[ 38.750007] mtdchar_read+0x108/0x2a0
[ 38.753679] __vfs_read+0x20/0x50
[ 38.757002] vfs_read+0xa4/0x190
[ 38.760237] ksys_read+0x6c/0xf0
[ 38.763471] __arm64_sys_read+0x20/0x30
[ 38.767319] el0_svc_common.constprop.3+0x90/0x160
[ 38.772125] do_el0_svc+0x28/0x90
[ 38.775449] el0_sync_handler+0x118/0x190
[ 38.779468] el0_sync+0x140/0x180
[ 38.782793] Code: 91000294 1400000f d50339bf f9405e80 (f90002c0)
[ 38.788910] ---[ end trace 55da560db4d6bef7 ]---
[ 38.793540] Kernel panic - not syncing: Fatal exception in interrupt
[ 38.799914] SMP: stopping secondary CPUs
[ 38.803849] Kernel Offset: disabled
[ 38.807344] CPU features: 0x10002,20006008
[ 38.811451] Memory Limit: none
[ 38.814513] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---

So it is clear that the "interruptible" part isn't handled correctly.
When the process receives a signal, one could either attempt a clean
abort (which appears to be difficult with this hardware) or just keep
restarting the sleep until the wait queue really completes. But checking
in a loop for -ERESTARTSYS is a bit too complicated for this driver, so
just make the sleep uninterruptible, to avoid all that nonsense.

The wait queue was actually restructured as a completion, after polling
other drivers for the most "popular" approach.

Fixes: 349ad66c0ab0 ("spi:Add Freescale DSPI driver for Vybrid VF610 platform")
Reported-by: Michael Walle <michael@walle.cc>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
Changes in v4:
Removed the dspi_disable_interrupts and dspi_enable_interrupts approach
and replaced it with this method.

Changes in v3:
Patch is new.

drivers/spi/spi-fsl-dspi.c | 19 ++++++-------------
1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 3ac004aa2abd..78c891e441cd 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -218,8 +218,7 @@ struct fsl_dspi {
u16 tx_cmd;
const struct fsl_dspi_devtype_data *devtype_data;

- wait_queue_head_t waitq;
- u32 waitflags;
+ struct completion xfer_done;

struct fsl_dspi_dma *dma;

@@ -899,10 +898,8 @@ static irqreturn_t dspi_interrupt(int irq, void *dev_id)
if (!(spi_sr & (SPI_SR_EOQF | SPI_SR_CMDTCF)))
return IRQ_NONE;

- if (dspi_rxtx(dspi) == 0) {
- dspi->waitflags = 1;
- wake_up_interruptible(&dspi->waitq);
- }
+ if (dspi_rxtx(dspi) == 0)
+ complete(&dspi->xfer_done);

return IRQ_HANDLED;
}
@@ -982,13 +979,9 @@ static int dspi_transfer_one_message(struct spi_controller *ctlr,
status = dspi_poll(dspi);
} while (status == -EINPROGRESS);
} else if (trans_mode != DSPI_DMA_MODE) {
- status = wait_event_interruptible(dspi->waitq,
- dspi->waitflags);
- dspi->waitflags = 0;
+ wait_for_completion(&dspi->xfer_done);
+ reinit_completion(&dspi->xfer_done);
}
- if (status)
- dev_err(&dspi->pdev->dev,
- "Waiting for transfer to complete failed!\n");

spi_transfer_delay_exec(transfer);
}
@@ -1368,7 +1361,7 @@ static int dspi_probe(struct platform_device *pdev)
goto out_clk_put;
}

- init_waitqueue_head(&dspi->waitq);
+ init_completion(&dspi->xfer_done);

poll_mode:

--
2.17.1
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