Bug 49381
| Summary: | [PATCH] [spi-mxs] "DMA transfer timeout" if execute spi_read() followed by spi_write() in DMA mode | ||
|---|---|---|---|
| Product: | Drivers | Reporter: | Pavel Nakonechny (pavel.nakonechny) |
| Component: | Other | Assignee: | drivers_other |
| Status: | NEW --- | ||
| Severity: | normal | CC: | alan, szg00000 |
| Priority: | P1 | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Kernel Version: | 3.6(upstream) | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
We can't accept patches via bugzilla. Please see Documentation/SubmittingPatches and send i via email to spi-devel-general@lists.sourceforge.net and cc marex@denx.de Please try this bug with latest kernel image. |
When spi-mxs driver works in DMA mode, calling to spi_read() after spi_write() hangs DMA channel: "DMA transfer timeout". To reproduce. Write simple driver with userspace interface allowing to manually call to spi_read() / spi_write(). Put spi-mxs.c driver in DMA mode by using buffer size more than restriction in "mxs_spi_transfer_one()". Or remove this restriction at all. Run spi_read() one or more times, then spi_write(). Fix. diff --git a/drivers/spi/spi-mxs.c b/drivers/spi/spi-mxs.c index edf1360..9dd69d4 100644 --- a/drivers/spi/spi-mxs.c +++ b/drivers/spi/spi-mxs.c @@ -247,6 +247,8 @@ static int mxs_spi_txrx_dma(struct mxs_spi *spi, int cs, ctrl0 |= BM_SSP_CTRL0_LOCK_CS; if (!write) ctrl0 |= BM_SSP_CTRL0_READ; + else + ctrl0 &= ~BM_SSP_CTRL0_READ; /* Queue the DMA data transfer. */ for (sg_count = 0; sg_count < sgs; sg_count++) { Additionally, DMA channel stays broken after this error. To fix this, apply following patch: diff --git a/drivers/spi/spi-mxs.c b/drivers/spi/spi-mxs.c index edf1360..db9d799 100644 --- a/drivers/spi/spi-mxs.c +++ b/drivers/spi/spi-mxs.c @@ -321,6 +321,7 @@ static int mxs_spi_txrx_dma(struct mxs_spi *spi, int cs, ret = wait_for_completion_timeout(&spi->c, msecs_to_jiffies(SSP_TIMEOUT)); if (!ret) { + ssp->dmach->device->device_control(ssp->dmach, DMA_TERMINATE_ALL, 0); dev_err(ssp->dev, "DMA transfer timeout\n"); ret = -ETIMEDOUT; goto err_vmalloc; Tested on i.MX287'based custom board. Sorry for this ridiculous english. :)