Re: 4430SDP boot failure - solved + SPI bug fix

Russell King - ARM Linux
2011-01-07T15:49:31Z

On Fri, Jan 07, 2011 at 07:56:34PM +0530, Santosh Shilimkar wrote:
> > -----Original Message-----
> > From: Russell King - ARM Linux [mailto:linux@arm.linux.org.uk]
> > Sent: Friday, January 07, 2011 7:55 PM
> > To: Santosh Shilimkar
> > Cc: linux-omap@vger.kernel.org; Tony Lindgren
> > Subject: Re: 4430SDP boot failure
> >
> > On Fri, Jan 07, 2011 at 06:39:06PM +0530, Santosh Shilimkar wrote:
> > > Have sent you latest bootloaders and full bootlog on my ES1.0
> > > OMAP4430SDP. 2.6.37 just boots fine for me.
> > >
> > > Low level debug as you reported seems to be broken though.
> >
> > Many thanks, the new mlo and uboot gets dhcp/tftp working nicely on
> > the board - which should ease the debugging problem as it no longer
> > requires anything but the reset button pressed to test a new kernel.
>
> Glad to hear that.

And, with one ARM errata disabled, the kernel finally boots. So the
"X-Loader hangs" message means that we did something that non-secure
mode prevented us from doing.

It would be a good idea if X-loader could tell dump out the exception,
register dump, and for data/prefetch aborts, the relevent FSR and FAR
registers - that would make debugging this kind of failure a lot
easier.

=================
Subject: Fix DMA API usage in OMAP MCSPI driver

Running the latest kernel on the 4430SDP board with DMA API debugging
enabled results in this:

WARNING: at lib/dma-debug.c:803 check_unmap+0x19c/0x6f0()
NULL NULL: DMA-API: device driver tries to free DMA memory it has not allocated
[device address=0x000000008129901a] [size=260 bytes]
Modules linked in:
Backtrace:
[<c003cbe0>] (dump_backtrace+0x0/0x10c) from [<c0278da8>] (dump_stack+0x18/0x1c)
r7:c1839dc0 r6:c0198578 r5:c0304b17 r4:00000323
[<c0278d90>] (dump_stack+0x0/0x1c) from [<c005b158>] (warn_slowpath_common+0x58/0x70)
[<c005b100>] (warn_slowpath_common+0x0/0x70) from [<c005b214>] (warn_slowpath_fmt+0x38/0x40)
r8:c1839e40 r7:00000000 r6:00000104 r5:00000000 r4:8129901a
[<c005b1dc>] (warn_slowpath_fmt+0x0/0x40) from [<c0198578>] (check_unmap+0x19c/0x6f0)
r3:c03110de r2:c0304e6b
[<c01983dc>] (check_unmap+0x0/0x6f0) from [<c0198cd8>] (debug_dma_unmap_page+0x74/0x80)
[<c0198c64>] (debug_dma_unmap_page+0x0/0x80) from [<c01d5ad8>] (omap2_mcspi_work+0x514/0xbf0)
[<c01d55c4>] (omap2_mcspi_work+0x0/0xbf0) from [<c006dfb0>] (process_one_work+0x294/0x400)
[<c006dd1c>] (process_one_work+0x0/0x400) from [<c006e50c>] (worker_thread+0x220/0x3f8)
[<c006e2ec>] (worker_thread+0x0/0x3f8) from [<c00738d0>] (kthread+0x88/0x90)
[<c0073848>] (kthread+0x0/0x90) from [<c005e924>] (do_exit+0x0/0x5fc)
r7:00000013 r6:c005e924 r5:c0073848 r4:c1829ee0
---[ end trace 1b75b31a2719ed20 ]---

I've no idea why this driver uses NULL for dma_unmap_single instead of
the &spi->dev that is laying around just waiting to be used in that
function - but it's an easy fix.

Also replace this comment with a FIXME comment:
/* Do DMA mapping "early" for better error reporting and
* dcache use. Note that if dma_unmap_single() ever starts
* to do real work on ARM, we'd need to clean up mappings
* for previous transfers on *ALL* exits of this loop...
*/
as the comment is not true - we do work in dma_unmap() functions,
particularly on ARMv6 and above. I've corrected the existing unmap
functions but if any others are required they must be added ASAP.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
I'm surprised this driver got merged as it has such a comment, and is
abusing the DMA API... well, at least with the DMA API debugging we
can now catch this stuff.

diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index 951a160..abb1ffb 100644
--- a/drivers/spi/omap2_mcspi.c
+++ b/drivers/spi/omap2_mcspi.c
@@ -397,7 +397,7 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)

if (tx != NULL) {
wait_for_completion(&mcspi_dma->dma_tx_completion);
- dma_unmap_single(NULL, xfer->tx_dma, count, DMA_TO_DEVICE);
+ dma_unmap_single(&spi->dev, xfer->tx_dma, count, DMA_TO_DEVICE);

/* for TX_ONLY mode, be sure all words have shifted out */
if (rx == NULL) {
@@ -412,7 +412,7 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)

if (rx != NULL) {
wait_for_completion(&mcspi_dma->dma_rx_completion);
- dma_unmap_single(NULL, xfer->rx_dma, count, DMA_FROM_DEVICE);
+ dma_unmap_single(&spi->dev, xfer->rx_dma, count, DMA_FROM_DEVICE);
omap2_mcspi_set_enable(spi, 0);

if (l & OMAP2_MCSPI_CHCONF_TURBO) {
@@ -1025,11 +1025,6 @@ static int omap2_mcspi_transfer(struct spi_device *spi, struct spi_message *m)
if (m->is_dma_mapped || len < DMA_MIN_BYTES)
continue;

- /* Do DMA mapping "early" for better error reporting and
- * dcache use. Note that if dma_unmap_single() ever starts
- * to do real work on ARM, we'd need to clean up mappings
- * for previous transfers on *ALL* exits of this loop...
- */
if (tx_buf != NULL) {
t->tx_dma = dma_map_single(&spi->dev, (void *) tx_buf,
len, DMA_TO_DEVICE);
@@ -1046,7 +1041,7 @@ static int omap2_mcspi_transfer(struct spi_device *spi, struct spi_message *m)
dev_dbg(&spi->dev, "dma %cX %d bytes error\n",
'R', len);
if (tx_buf != NULL)
- dma_unmap_single(NULL, t->tx_dma,
+ dma_unmap_single(&spi->dev, t->tx_dma,
len, DMA_TO_DEVICE);
return -EINVAL;
}