linux-kernel - [PATCH 2/4] phy: rockchip-emmc: configure frequency range and drive impedance

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Message-Id: <1463092986-61777-2-git-send-email-briannorris@chromium.org>
Date:	Thu, 12 May 2016 15:43:04 -0700
From:	Brian Norris <briannorris@...omium.org>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Heiko Stuebner <heiko@...ech.de>, <linux-kernel@...r.kernel.org>,
	<linux-rockchip@...ts.infradead.org>,
	Doug Anderson <dianders@...omium.org>,
	Shawn Lin <shawn.lin@...k-chips.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	Brian Norris <computersforpeace@...il.com>,
	Brian Norris <briannorris@...omium.org>
Subject: [PATCH 2/4] phy: rockchip-emmc: configure frequency range and drive impedance

From: Shawn Lin <shawn.lin@...k-chips.com>

Signal integrity analysis has suggested we set these values. Do this in
power_on(), so that they get reconfigured after suspend/resume.

Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
Signed-off-by: Brian Norris <briannorris@...omium.org>
---
 drivers/phy/phy-rockchip-emmc.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/phy/phy-rockchip-emmc.c b/drivers/phy/phy-rockchip-emmc.c
index 48cbe691a889..5641dede32f6 100644
--- a/drivers/phy/phy-rockchip-emmc.c
+++ b/drivers/phy/phy-rockchip-emmc.c
@@ -56,6 +56,19 @@
 #define PHYCTRL_DLLRDY_SHIFT	0x5
 #define PHYCTRL_DLLRDY_DONE	0x1
 #define PHYCTRL_DLLRDY_GOING	0x0
+#define PHYCTRL_FREQSEL_200M	0x0
+#define PHYCTRL_FREQSEL_50M	0x1
+#define PHYCTRL_FREQSEL_100M	0x2
+#define PHYCTRL_FREQSEL_150M	0x3
+#define PHYCTRL_FREQSEL_MASK	0x3
+#define PHYCTRL_FREQSEL_SHIFT	0xc
+#define PHYCTRL_DR_MASK		0x7
+#define PHYCTRL_DR_SHIFT	0x4
+#define PHYCTRL_DR_50OHM	0x0
+#define PHYCTRL_DR_33OHM	0x1
+#define PHYCTRL_DR_66OHM	0x2
+#define PHYCTRL_DR_100OHM	0x3
+#define PHYCTRL_DR_40OHM	0x4
 
 struct rockchip_emmc_phy {
 	unsigned int	reg_offset;
@@ -154,6 +167,20 @@ static int rockchip_emmc_phy_power_on(struct phy *phy)
 	struct rockchip_emmc_phy *rk_phy = phy_get_drvdata(phy);
 	int ret = 0;
 
+	/* DLL operation: 170 to 200 MHz */
+	regmap_write(rk_phy->reg_base,
+		     rk_phy->reg_offset + GRF_EMMCPHY_CON0,
+		     HIWORD_UPDATE(PHYCTRL_FREQSEL_200M,
+				   PHYCTRL_FREQSEL_MASK,
+				   PHYCTRL_FREQSEL_SHIFT));
+
+	/* Drive impedance: 50 Ohm */
+	regmap_write(rk_phy->reg_base,
+		     rk_phy->reg_offset + GRF_EMMCPHY_CON6,
+		     HIWORD_UPDATE(PHYCTRL_DR_50OHM,
+				   PHYCTRL_DR_MASK,
+				   PHYCTRL_DR_SHIFT));
+
 	/* Power up emmc phy analog blocks */
 	ret = rockchip_emmc_phy_power(rk_phy, PHYCTRL_PDB_PWR_ON);
 	if (ret)
-- 
2.8.0.rc3.226.g39d4020