[PATCH net-next v3 1/4] net: ipa: fix assumptions about DMA address size

From: Alex Elder <elder@linaro.org>
To: davem@davemloft.net, kuba@kernel.org
Cc: f.fainelli@gmail.com, bjorn.andersson@linaro.org,
	evgreen@chromium.org, cpratapa@codeaurora.org,
	subashab@codeaurora.org, elder@kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH net-next v3 1/4] net: ipa: fix assumptions about DMA address size
Date: Thu, 18 Mar 2021 13:59:27 -0500	[thread overview]
Message-ID: <20210318185930.891260-2-elder@linaro.org> (raw)
In-Reply-To: <20210318185930.891260-1-elder@linaro.org>

Some build time checks in ipa_table_validate_build() assume that a
DMA address is 64 bits wide.  That is more restrictive than it has
to be.  A route or filter table is 64 bits wide no matter what the
size of a DMA address is on the AP.  The code actually uses a
pointer to __le64 to access table entries, and a fixed constant
IPA_TABLE_ENTRY_SIZE to describe the size of those entries.

Loosen up two checks so they still verify some requirements, but
such that they do not assume the size of a DMA address is 64 bits.

Signed-off-by: Alex Elder <elder@linaro.org>
---
 drivers/net/ipa/ipa_table.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ipa/ipa_table.c b/drivers/net/ipa/ipa_table.c
index 7450e27068f19..dd07fe9dd87a3 100644
--- a/drivers/net/ipa/ipa_table.c
+++ b/drivers/net/ipa/ipa_table.c
@@ -126,13 +126,15 @@ static void ipa_table_validate_build(void)
 	 */
 	BUILD_BUG_ON(ARCH_DMA_MINALIGN % IPA_TABLE_ALIGN);
 
-	/* Filter and route tables contain DMA addresses that refer to
-	 * filter or route rules.  We use a fixed constant to represent
-	 * the size of either type of table entry.  Code in ipa_table_init()
-	 * uses a pointer to __le64 to initialize table entriews.
+	/* Filter and route tables contain DMA addresses that refer
+	 * to filter or route rules.  But the size of a table entry
+	 * is 64 bits regardless of what the size of an AP DMA address
+	 * is.  A fixed constant defines the size of an entry, and
+	 * code in ipa_table_init() uses a pointer to __le64 to
+	 * initialize tables.
 	 */
-	BUILD_BUG_ON(IPA_TABLE_ENTRY_SIZE != sizeof(dma_addr_t));
-	BUILD_BUG_ON(sizeof(dma_addr_t) != sizeof(__le64));
+	BUILD_BUG_ON(sizeof(dma_addr_t) > IPA_TABLE_ENTRY_SIZE);
+	BUILD_BUG_ON(sizeof(__le64) != IPA_TABLE_ENTRY_SIZE);
 
 	/* A "zero rule" is used to represent no filtering or no routing.
 	 * It is a 64-bit block of zeroed memory.  Code in ipa_table_init()
-- 
2.27.0

