linux-kernel - [PATCH 1/2] spi/rockchip: fix bug that case spi can't go as fast as slave request

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Message-Id: <1413372349-4254-1-git-send-email-addy.ke@rock-chips.com>
Date:	Wed, 15 Oct 2014 19:25:49 +0800
From:	Addy Ke <addy.ke@...k-chips.com>
To:	broonie@...nel.org, heiko@...ech.de, dianders@...omium.org,
	grant.likely@...aro.org, robh+dt@...nel.org, amstan@...gle.com,
	sonnyrao@...gle.com
Cc:	linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org,
	olof@...om.net, hj@...k-chips.com, kever.yang@...k-chips.com,
	xjq@...k-chips.com, huangtao@...k-chips.com, zyw@...k-chips.com,
	yzq@...k-chips.com, zhenfu.fang@...k-chips.com, cf@...k-chips.com,
	zhangqing@...k-chips.com, hl@...k-chips.com,
	wei.luo@...k-chips.com, Addy Ke <addy.ke@...k-chips.com>
Subject: [PATCH 1/2] spi/rockchip: fix bug that case spi can't go as fast as slave request

Because the minimum divisor in rk3x's spi controller is 2,
if spi_clk is less than 2 * sclk_out, we can't get the right divisor.
So we must set spi_clk again to match slave request.

Signed-off-by: Addy Ke <addy.ke@...k-chips.com>
---
 drivers/spi/spi-rockchip.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index f96ea8a..3044c6c 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -145,6 +145,9 @@
 #define RXBUSY						(1 << 0)
 #define TXBUSY						(1 << 1)
 
+/* sclk_out: spi master internal logic in rk3x can support 50Mhz */
+#define MAX_SCLK_OUT		50000000
+
 enum rockchip_ssi_type {
 	SSI_MOTO_SPI = 0,
 	SSI_TI_SSP,
@@ -496,6 +499,15 @@ static void rockchip_spi_config(struct rockchip_spi *rs)
 			dmacr |= RF_DMA_EN;
 	}
 
+	if (WARN_ON(rs->speed > MAX_SCLK_OUT))
+		rs->speed = MAX_SCLK_OUT;
+
+	/* the minimum divsor is 2 */
+	if (rs->max_freq < 2 * rs->speed) {
+		clk_set_rate(rs->spiclk, 2 * rs->speed);
+		rs->max_freq = clk_get_rate(rs->spiclk);
+	}
+
 	/* div doesn't support odd number */
 	div = max_t(u32, rs->max_freq / rs->speed, 1);
 	div = (div + 1) & 0xfffe;
-- 
1.8.3.2


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