• Alexey Brodkin's avatar
    stmmac: troubleshoot unexpected bits in des0 & des1 · 86a88cf3
    Alexey Brodkin authored
    commit f1590670 upstream.
    
    Current implementation of descriptor init procedure only takes
    care about setting/clearing ownership flag in "des0"/"des1"
    fields while it is perfectly possible to get unexpected bits
    set because of the following factors:
    
     [1] On driver probe underlying memory allocated with
         dma_alloc_coherent() might not be zeroed and so
         it will be filled with garbage.
    
     [2] During driver operation some bits could be set by SD/MMC
         controller (for example error flags etc).
    
    And unexpected and/or randomly set flags in "des0"/"des1"
    fields may lead to unpredictable behavior of GMAC DMA block.
    
    This change addresses both items above with:
    
     [1] Use of dma_zalloc_coherent() instead of simple
         dma_alloc_coherent() to make sure allocated memory is
         zeroed. That shouldn't affect performance because
         this allocation only happens once on driver probe.
    
     [2] Do explicit zeroing of both "des0" and "des1" fields
         of all buffer descriptors during initialization of
         DMA transfer.
    
    And while at it fixed identation of dma_free_coherent()
    counterpart as well.
    Signed-off-by: default avatarAlexey Brodkin <abrodkin@synopsys.com>
    Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
    Cc: arc-linux-dev@synopsys.com
    Cc: linux-kernel@vger.kernel.org
    Cc: David Miller <davem@davemloft.net>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
    86a88cf3
enh_desc.c 10.7 KB