From f1590670ce069eefeb93916391a67643e6ad1630 Mon Sep 17 00:00:00 2001 From: Alexey Brodkin Date: Wed, 24 Jun 2015 11:47:41 +0300 Subject: stmmac: troubleshoot unexpected bits in des0 & des1 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: Alexey Brodkin Cc: Giuseppe Cavallaro Cc: arc-linux-dev@synopsys.com Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org Cc: David Miller Signed-off-by: David S. Miller --- drivers/net/ethernet/stmicro/stmmac/enh_desc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'drivers/net/ethernet/stmicro/stmmac/enh_desc.c') diff --git a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c index 1e2bcf5f89e1..7d944449f5ef 100644 --- a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c +++ b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c @@ -240,6 +240,7 @@ static int enh_desc_get_rx_status(void *data, struct stmmac_extra_stats *x, static void enh_desc_init_rx_desc(struct dma_desc *p, int disable_rx_ic, int mode, int end) { + p->des01.all_flags = 0; p->des01.erx.own = 1; p->des01.erx.buffer1_size = BUF_SIZE_8KiB - 1; @@ -254,7 +255,7 @@ static void enh_desc_init_rx_desc(struct dma_desc *p, int disable_rx_ic, static void enh_desc_init_tx_desc(struct dma_desc *p, int mode, int end) { - p->des01.etx.own = 0; + p->des01.all_flags = 0; if (mode == STMMAC_CHAIN_MODE) ehn_desc_tx_set_on_chain(p, end); else -- cgit v1.2.3