• Sebastian Andrzej Siewior's avatar
    usb: core: buffer: smallest buffer should start at ARCH_DMA_MINALIGN · 47a97363
    Sebastian Andrzej Siewior authored
    commit 5efd2ea8 upstream.
    
    the following error pops up during "testusb -a -t 10"
    | musb-hdrc musb-hdrc.1.auto: dma_pool_free buffer-128,	f134e000/be842000 (bad dma)
    hcd_buffer_create() creates a few buffers, the smallest has 32 bytes of
    size. ARCH_KMALLOC_MINALIGN is set to 64 bytes. This combo results in
    hcd_buffer_alloc() returning memory which is 32 bytes aligned and it
    might by identified by buffer_offset() as another buffer. This means the
    buffer which is on a 32 byte boundary will not get freed, instead it
    tries to free another buffer with the error message.
    
    This patch fixes the issue by creating the smallest DMA buffer with the
    size of ARCH_KMALLOC_MINALIGN (or 32 in case ARCH_KMALLOC_MINALIGN is
    smaller). This might be 32, 64 or even 128 bytes. The next three pools
    will have the size 128, 512 and 2048.
    In case the smallest pool is 128 bytes then we have only three pools
    instead of four (and zero the first entry in the array).
    The last pool size is always 2048 bytes which is the assumed PAGE_SIZE /
    2 of 4096. I doubt it makes sense to continue using PAGE_SIZE / 2 where
    we would end up with 8KiB buffer in case we have 16KiB pages.
    Instead I think it makes sense to have a common size(s) and extend them
    if there is need to.
    There is a BUILD_BUG_ON() now in case someone has a minalign of more than
    128 bytes.
    Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
    Acked-by: default avatarAlan Stern <stern@rowland.harvard.edu>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
    47a97363
buffer.c 3.49 KB