linux-kernel - [PATCH net-next 2/4] net: ipa: introduce dma_addr

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Message-Id: <20210317222946.118125-3-elder@linaro.org>
Date:   Wed, 17 Mar 2021 17:29:44 -0500
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     bjorn.andersson@...aro.org, evgreen@...omium.org,
        cpratapa@...eaurora.org, subashab@...eaurora.org, elder@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next 2/4] net: ipa: introduce dma_addr_high32()

Create a new helper function to encapsulate extracting the
high-order 32 bits of a DMA address.  It returns 0 for builds
in which a DMA address is not 64 bits.

This avoids doing a 32-position shift on a DMA address if it
happens not to be 64 bits wide.

Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ipa/gsi.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index 2119367b93ea9..53698c64cf882 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -688,6 +688,16 @@ static void gsi_evt_ring_doorbell(struct gsi *gsi, u32 evt_ring_id, u32 index)
 	iowrite32(val, gsi->virt + GSI_EV_CH_E_DOORBELL_0_OFFSET(evt_ring_id));
 }
 
+/* Encapsulate extracting high-order 32 bits of DMA address */
+static u32 dma_addr_high32(dma_addr_t addr)
+{
+#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
+	return (u32)(addr >> 32);
+#else /* !CONFIG_ARCH_DMA_ADDR_T_64BIT */
+	return 0;
+#endif /* !CONFIG_ARCH_DMA_ADDR_T_64BIT */
+}
+
 /* Program an event ring for use */
 static void gsi_evt_ring_program(struct gsi *gsi, u32 evt_ring_id)
 {
@@ -711,7 +721,7 @@ static void gsi_evt_ring_program(struct gsi *gsi, u32 evt_ring_id)
 	val = evt_ring->ring.addr & GENMASK(31, 0);
 	iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_2_OFFSET(evt_ring_id));
 
-	val = evt_ring->ring.addr >> 32;
+	val = dma_addr_high32(evt_ring->ring.addr);
 	iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_3_OFFSET(evt_ring_id));
 
 	/* Enable interrupt moderation by setting the moderation delay */
@@ -819,7 +829,7 @@ static void gsi_channel_program(struct gsi_channel *channel, bool doorbell)
 	val = channel->tre_ring.addr & GENMASK(31, 0);
 	iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_2_OFFSET(channel_id));
 
-	val = channel->tre_ring.addr >> 32;
+	val = dma_addr_high32(channel->tre_ring.addr);
 	iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_3_OFFSET(channel_id));
 
 	/* Command channel gets low weighted round-robin priority */
-- 
2.27.0