linux-kernel - [PATCH v1] dmaengine: tegra: Use relaxed versions of readl/writel

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Date:   Thu, 25 Apr 2019 02:17:08 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Laxman Dewangan <ldewangan@...dia.com>,
        Vinod Koul <vkoul@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>
Cc:     dmaengine@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v1] dmaengine: tegra: Use relaxed versions of readl/writel

The readl/writel functions are inserting memory barrier in order to
ensure that memory stores are completed. On Tegra20 and Tegra30 this
results in L2 cache syncing which isn't a cheapest operation. The
tegra20-apb-dma driver doesn't need to synchronize generic memory
accesses, hence use the relaxed versions of the functions.

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/dma/tegra20-apb-dma.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index cf462b1abc0b..e646e1c7b299 100644
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -241,23 +241,23 @@ struct tegra_dma {
 
 static inline void tdma_write(struct tegra_dma *tdma, u32 reg, u32 val)
 {
-	writel(val, tdma->base_addr + reg);
+	writel_relaxed(val, tdma->base_addr + reg);
 }
 
 static inline u32 tdma_read(struct tegra_dma *tdma, u32 reg)
 {
-	return readl(tdma->base_addr + reg);
+	return readl_relaxed(tdma->base_addr + reg);
 }
 
 static inline void tdc_write(struct tegra_dma_channel *tdc,
 		u32 reg, u32 val)
 {
-	writel(val, tdc->chan_addr + reg);
+	writel_relaxed(val, tdc->chan_addr + reg);
 }
 
 static inline u32 tdc_read(struct tegra_dma_channel *tdc, u32 reg)
 {
-	return readl(tdc->chan_addr + reg);
+	return readl_relaxed(tdc->chan_addr + reg);
 }
 
 static inline struct tegra_dma_channel *to_tegra_dma_chan(struct dma_chan *dc)
-- 
2.21.0