• Russell King - ARM Linux's avatar
    spi/omap: Fix DMA API usage in OMAP MCSPI driver · 07fe0351
    Russell King - ARM Linux authored
    
    
    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: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    Acked-by: default avatarTony Lindgren <tony@atomide.com>
    Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
    07fe0351