linux-kernel - [PATCH v1 11/14] spi: rockchip: precompute rx sample delay

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Date:   Wed, 31 Oct 2018 11:57:08 +0100
From:   Emil Renner Berthing <esmil@...lme.dk>
To:     linux-spi@...r.kernel.org
Cc:     Emil Renner Berthing <kernel@...il.dk>,
        Addy Ke <addy.ke@...k-chips.com>,
        Mark Brown <broonie@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 11/14] spi: rockchip: precompute rx sample delay

From: Emil Renner Berthing <kernel@...il.dk>

Now that we no longer potentially change spi clock
at runtime we can precompute the rx sample delay
at probe time rather than for each transfer.

Signed-off-by: Emil Renner Berthing <kernel@...il.dk>
---
 drivers/spi/spi-rockchip.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index d1b3ba2b1532..5fe6099ff366 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -94,6 +94,7 @@
 #define CR0_BHT_8BIT				0x1
 
 #define CR0_RSD_OFFSET				14
+#define CR0_RSD_MAX				0x3
 
 #define CR0_FRF_OFFSET				16
 #define CR0_FRF_SPI					0x0
@@ -179,7 +180,7 @@ struct rockchip_spi {
 	u32 freq;
 
 	u8 n_bytes;
-	u32 rsd_nsecs;
+	u8 rsd;
 
 	const void *tx;
 	const void *tx_end;
@@ -450,13 +451,13 @@ static void rockchip_spi_config(struct rockchip_spi *rs,
 		bool use_dma)
 {
 	u32 dmacr = 0;
-	int rsd = 0;
 
 	u32 cr0 = CR0_FRF_SPI  << CR0_FRF_OFFSET
 	        | CR0_BHT_8BIT << CR0_BHT_OFFSET
 	        | CR0_SSD_ONE  << CR0_SSD_OFFSET
 	        | CR0_EM_BIG   << CR0_EM_OFFSET;
 
+	cr0 |= rs->rsd << CR0_RSD_OFFSET;
 	cr0 |= (rs->n_bytes << CR0_DFS_OFFSET);
 	cr0 |= (spi->mode & 0x3U) << CR0_SCPH_OFFSET;
 
@@ -474,20 +475,6 @@ static void rockchip_spi_config(struct rockchip_spi *rs,
 			dmacr |= RF_DMA_EN;
 	}
 
-	/* Rx sample delay is expressed in parent clock cycles (max 3) */
-	rsd = DIV_ROUND_CLOSEST(rs->rsd_nsecs * (rs->freq >> 8),
-				1000000000 >> 8);
-	if (!rsd && rs->rsd_nsecs) {
-		pr_warn_once("rockchip-spi: %u Hz are too slow to express %u ns delay\n",
-			     rs->freq, rs->rsd_nsecs);
-	} else if (rsd > 3) {
-		rsd = 3;
-		pr_warn_once("rockchip-spi: %u Hz are too fast to express %u ns delay, clamping at %u ns\n",
-			     rs->freq, rs->rsd_nsecs,
-			     rsd * 1000000000U / rs->freq);
-	}
-	cr0 |= rsd << CR0_RSD_OFFSET;
-
 	writel_relaxed(cr0, rs->regs + ROCKCHIP_SPI_CTRLR0);
 
 	if (rs->n_bytes == 1)
@@ -620,8 +607,21 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 	rs->freq = clk_get_rate(rs->spiclk);
 
 	if (!of_property_read_u32(pdev->dev.of_node, "rx-sample-delay-ns",
-				  &rsd_nsecs))
-		rs->rsd_nsecs = rsd_nsecs;
+				  &rsd_nsecs)) {
+		/* rx sample delay is expressed in parent clock cycles (max 3) */
+		u32 rsd = DIV_ROUND_CLOSEST(rsd_nsecs * (rs->freq >> 8),
+				1000000000 >> 8);
+		if (!rsd) {
+			dev_warn(rs->dev, "%u Hz are too slow to express %u ns delay\n",
+					rs->freq, rsd_nsecs);
+		} else if (rsd > CR0_RSD_MAX) {
+			rsd = CR0_RSD_MAX;
+			dev_warn(rs->dev, "%u Hz are too fast to express %u ns delay, clamping at %u ns\n",
+					rs->freq, rsd_nsecs,
+					CR0_RSD_MAX * 1000000000U / rs->freq);
+		}
+		rs->rsd = rsd;
+	}
 
 	rs->fifo_len = get_fifo_len(rs);
 	if (!rs->fifo_len) {
-- 
2.19.1