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Commit f1590670 authored by Alexey Brodkin's avatar Alexey Brodkin Committed by David S. Miller
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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: 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: stable@vger.kernel.org
Cc: David Miller <davem@davemloft.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 34b99df4

drivers/net/ethernet/stmicro/stmmac/descs.h

+2 −0
Original line number Diff line number Diff line
@@ -158,6 +158,8 @@ struct dma_desc { 
			u32 buffer2_size:13;

			u32 reserved4:3;

		} etx;		/* -- enhanced -- */



		u64 all_flags;

	} des01;

	unsigned int des2;

	unsigned int des3;

drivers/net/ethernet/stmicro/stmmac/enh_desc.c

+2 −1
Original line number Diff line number Diff line
@@ -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

drivers/net/ethernet/stmicro/stmmac/norm_desc.c

+2 −1
Original line number Diff line number Diff line
@@ -123,6 +123,7 @@ static int ndesc_get_rx_status(void *data, struct stmmac_extra_stats *x, 
static void ndesc_init_rx_desc(struct dma_desc *p, int disable_rx_ic, int mode,

			       int end)

{

	p->des01.all_flags = 0;

	p->des01.rx.own = 1;

	p->des01.rx.buffer1_size = BUF_SIZE_2KiB - 1;
@@ -137,7 +138,7 @@ static void ndesc_init_rx_desc(struct dma_desc *p, int disable_rx_ic, int mode, 


static void ndesc_init_tx_desc(struct dma_desc *p, int mode, int end)

{

	p->des01.tx.own = 0;

	p->des01.all_flags = 0;

	if (mode == STMMAC_CHAIN_MODE)

		ndesc_tx_set_on_chain(p, end);

	else

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

+22 −22
Original line number Diff line number Diff line
@@ -1189,7 +1189,7 @@ static int alloc_dma_desc_resources(struct stmmac_priv *priv) 
		goto err_tx_skbuff;



	if (priv->extend_desc) {

		priv->dma_erx = dma_alloc_coherent(priv->device, rxsize *

		priv->dma_erx = dma_zalloc_coherent(priv->device, rxsize *

						    sizeof(struct

							   dma_extended_desc),

						    &priv->dma_rx_phy,
@@ -1197,7 +1197,7 @@ static int alloc_dma_desc_resources(struct stmmac_priv *priv) 
		if (!priv->dma_erx)

			goto err_dma;



		priv->dma_etx = dma_alloc_coherent(priv->device, txsize *

		priv->dma_etx = dma_zalloc_coherent(priv->device, txsize *

						    sizeof(struct

							   dma_extended_desc),

						    &priv->dma_tx_phy,
@@ -1209,14 +1209,14 @@ static int alloc_dma_desc_resources(struct stmmac_priv *priv) 
			goto err_dma;

		}

	} else {

		priv->dma_rx = dma_alloc_coherent(priv->device, rxsize *

		priv->dma_rx = dma_zalloc_coherent(priv->device, rxsize *

						   sizeof(struct dma_desc),

						   &priv->dma_rx_phy,

						   GFP_KERNEL);

		if (!priv->dma_rx)

			goto err_dma;



		priv->dma_tx = dma_alloc_coherent(priv->device, txsize *

		priv->dma_tx = dma_zalloc_coherent(priv->device, txsize *

						   sizeof(struct dma_desc),

						   &priv->dma_tx_phy,

						   GFP_KERNEL);