linux-kernel - RE: [PATCH]iwlan dma mapping read and write changes

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Message-ID: <6F5C1D715B2DA5498A628E6B9C124F04F633E2CD@hasmsx504.ger.corp.intel.com>
Date:	Wed, 11 Feb 2009 23:27:58 +0200
From:	"Winkler, Tomas" <tomas.winkler@...el.com>
To:	"Yu, Fenghua" <fenghua.yu@...el.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.sc.intel.com>,
	Johannes Berg <johannes@...solutions.net>,
	"Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>,
	"Zhu, Yi" <yi.zhu@...el.com>, Chris Wright <chrisw@...s-sol.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: RE: [PATCH]iwlan dma mapping read and write changes



>-----Original Message-----
>From: Yu, Fenghua
>Sent: Wednesday, February 11, 2009 8:27 PM
>To: David Woodhouse; Ingo Molnar; Stephen Rothwell; Andrew Morton; Johannes
>Berg; Grumbach, Emmanuel; Winkler, Tomas; Zhu, Yi; Chris Wright
>Cc: LKML; iommu@...ts.linux-foundation.org
>Subject: [PATCH]iwlan dma mapping read and write changes
>
>When iwlan runs on IOMMU, IOMMU generates a lot of PTE write faults because
>PTE
>write bit is not set on some of PTE's. This is because iwlan driver calls
>DMA
>mapping with PCI_DMA_TODEVICE which is read only in mapping PTE. But iwlan
>device
>actually writes to the mapped page to update its contents. This issue is
>not
>exposed in swiotlb. But VT-d hardware can capture this fault and stop the
>fault
>transaction.
>
>The following patch fixes the issue.
>
>Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Acked-by: Tomas Winkler <tomas.winkler@...el.com>

Indeed the firmware/ucode write back to host memory to update retry counter for APMDU packets. I'm not sure if this is needed for legacy traffic, though.   

>---
>
> iwl-tx.c |    8 ++++----
> 1 files changed, 4 insertions(+), 4 deletions(-)
>
>--- a/drivers/net/wireless/iwlwifi/iwl-tx.c.orig	2009-02-10
>21:28:45.000000000 -0800
>+++ b/drivers/net/wireless/iwlwifi/iwl-tx.c	2009-02-10
>21:41:02.000000000 -0800
>@@ -148,7 +148,7 @@ static void iwl_hw_txq_free_tfd(struct i
> 		pci_unmap_single(dev,
> 				pci_unmap_addr(&txq->cmd[index]->meta, mapping),
> 				pci_unmap_len(&txq->cmd[index]->meta, len),
>-				PCI_DMA_TODEVICE);
>+				PCI_DMA_BIDIRECTIONAL);
>
> 	/* Unmap chunks, if any. */
> 	for (i = 1; i < num_tbs; i++) {
>@@ -964,7 +964,7 @@ int iwl_tx_skb(struct iwl_priv *priv, st
> 	 * within command buffer array. */
> 	txcmd_phys = pci_map_single(priv->pci_dev,
> 				    out_cmd, sizeof(struct iwl_cmd),
>-				    PCI_DMA_TODEVICE);
>+				    PCI_DMA_BIDIRECTIONAL);
> 	pci_unmap_addr_set(&out_cmd->meta, mapping, txcmd_phys);
> 	pci_unmap_len_set(&out_cmd->meta, len, sizeof(struct iwl_cmd));
> 	/* Add buffer containing Tx command and MAC(!) header to TFD's
>@@ -1115,7 +1115,7 @@ int iwl_enqueue_hcmd(struct iwl_priv *pr
> 			IWL_MAX_SCAN_SIZE : sizeof(struct iwl_cmd);
>
> 	phys_addr = pci_map_single(priv->pci_dev, out_cmd,
>-				   len, PCI_DMA_TODEVICE);
>+				   len, PCI_DMA_BIDIRECTIONAL);
> 	pci_unmap_addr_set(&out_cmd->meta, mapping, phys_addr);
> 	pci_unmap_len_set(&out_cmd->meta, len, len);
> 	phys_addr += offsetof(struct iwl_cmd, hdr);
>@@ -1212,7 +1212,7 @@ static void iwl_hcmd_queue_reclaim(struc
> 	pci_unmap_single(priv->pci_dev,
> 		pci_unmap_addr(&txq->cmd[cmd_idx]->meta, mapping),
> 		pci_unmap_len(&txq->cmd[cmd_idx]->meta, len),
>-		PCI_DMA_TODEVICE);
>+		PCI_DMA_BIDIRECTIONAL);
>
> 	for (idx = iwl_queue_inc_wrap(idx, q->n_bd); q->read_ptr != idx;
> 	     q->read_ptr = iwl_queue_inc_wrap(q->read_ptr, q->n_bd)) {
---------------------------------------------------------------------
Intel Israel (74) Limited

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