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

Santosh Shilimkar
2011-01-07T18:25:14Z

> -----Original Message-----
> From: linux-omap-owner@vger.kernel.org [mailto:linux-omap-
> owner@vger.kernel.org] On Behalf Of Russell King - ARM Linux
> Sent: Friday, January 07, 2011 9:19 PM
> To: Santosh Shilimkar
> Cc: linux-omap@vger.kernel.org; Tony Lindgren
> Subject: Re: 4430SDP boot failure - solved + SPI bug fix
>
> 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.
>
Actually it's not. The error message is quite misleading. Basically in
x-loader exception handlers are setup and all these handlers report
same message ("X-Loader hangs"). This should be fixed so that it can
report more meaningful info like data abort, prefetch abort etc.

Till the vector relocation in the kernel exceptions are not set up
so code jumps to already installed exceptions in the x-loader and
hence the messege.

> 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.
>
Yes. At least it should report data/prefect aborts.

> =================
> 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>

Thanks for fixing it
> ---
> 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;
> }
>
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