[PATCH V6 1/2] PHY: Exynos: Add Exynos5250 SATA PHY driver

On Fri, Jan 10, 2014 at 8:35 PM, Tomasz Figa [off-list ref] wrote:

Hi Yuvaraj,

In general this version looks pretty good, but I have some questions inline.

On 10.01.2014 08:00, Yuvaraj Kumar C D wrote:
[snip]

quoted

diff --git a/drivers/phy/phy-exynos5250-sata-i2c.c

b/drivers/phy/phy-exynos5250-sata-i2c.c
new file mode 100644
index 0000000..206e337

--- /dev/null
+++ b/drivers/phy/phy-exynos5250-sata-i2c.c

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2013 Samsung Electronics Co.Ltd
+ * Author:
+ *     Yuvaraj C D <yuvaraj.cd@samsung.com>
+ *
+ * This program is free software; you can redistribute  it and/or modify

it
+ * under  the terms of  the GNU General  Public License as published by
the
+ * Free Software Foundation;  either version 2 of the  License, or (at
your
+ * option) any later version.
+ *
+ */
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+static int exynos_sata_i2c_probe(struct i2c_client *client,
+               const struct i2c_device_id *i2c_id)
+{
+       return 0;
+}
+
+static const struct i2c_device_id sataphy_i2c_device_match[] = {
+       { "exynos-sataphy-i2c", 0 },
+};
+
+static struct i2c_driver sataphy_i2c_driver = {
+       .probe          = exynos_sata_i2c_probe,
+       .id_table       = sataphy_i2c_device_match,
+       .driver   = {
+               .name = "exynos-sataphy-i2c",
+               .owner = THIS_MODULE,
+       },
+};
+
+static int __init exynos5250_phy_i2c_init(void)
+{
+       return i2c_add_driver(&sataphy_i2c_driver);
+}
+module_init(exynos5250_phy_i2c_init);

Hmm, is this driver even necessary now?

Wolfram, would it be possible to use an i2c_client without a driver bound to
it?

quoted

diff --git a/drivers/phy/phy-exynos5250-sata.c

b/drivers/phy/phy-exynos5250-sata.c
new file mode 100644
index 0000000..6e5ff8d

--- /dev/null
+++ b/drivers/phy/phy-exynos5250-sata.c

@@ -0,0 +1,238 @@
+/*
+ * Samsung SATA SerDes(PHY) driver
+ *
+ * Copyright (C) 2013 Samsung Electronics Co., Ltd.
+ * Authors: Girish K S <ks.giri@samsung.com>
+ *         Yuvaraj Kumar C D <yuvaraj.cd@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/phy/phy.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/spinlock.h>
+#include <linux/mfd/syscon.h>
+
+#define EXYNOS5_SATA_RESET             0x4
+#define RESET_CMN_RST_N                        (1 << 1)
+#define LINK_RESET                     0xF0000

nit: Lowercase is preferred in hexadecimal notation.
+ all other occurrences in this file.

quoted

+#define EXYNOS5_SATA_MODE0             0x10
+#define EXYNOS5_SATAPHY_PMU_ENABLE     (1 << 0)
+#define SATA_SPD_GEN3                  (2 << 0)
+#define EXYNOS5_SATA_CTRL0             0x14
+#define CTRL0_P0_PHY_CALIBRATED_SEL    (1 << 9)
+#define CTRL0_P0_PHY_CALIBRATED                (1 << 8)
+#define EXYNOS5_SATA_PHSATA_CTRLM      0xE0
+#define PHCTRLM_REF_RATE               (1 << 1)
+#define PHCTRLM_HIGH_SPEED             (1 << 0)
+#define EXYNOS5_SATA_PHSATA_STATM      0xF0
+#define PHSTATM_PLL_LOCKED             (1 << 0)
+#define EXYNOS_SATA_PHY_EN             (1 << 0)
+#define SATAPHY_CONTROL_OFFSET         0x0724
+
+struct exynos_sata_phy {
+       struct phy *phy;
+       struct clk *phyclk;
+       void __iomem *regs;
+       void __iomem *pmureg;
+       struct i2c_client *client;
+};
+
+static bool wait_for_reg_status(void __iomem *base, u32 reg, u32
checkbit,
+                               u32 status)
+{
+       unsigned long timeout = jiffies + usecs_to_jiffies(1000);

nit: It would be better to define the timeout using a macro to not use magic
numbers.

quoted

+
+       while (time_before(jiffies, timeout)) {
+               if ((readl(base + reg) & checkbit) == status)
+                       return true;
+       }
+
+       return false;
+}
+
+static int exynos_sata_phy_power_on(struct phy *phy)
+{
+       struct exynos_sata_phy *sata_phy = phy_get_drvdata(phy);
+
+       regmap_update_bits(sata_phy->pmureg, SATAPHY_CONTROL_OFFSET,
+                       EXYNOS5_SATAPHY_PMU_ENABLE, EXYNOS_SATA_PHY_EN);

regmap_update_bits can return an error. Wouldn't it be better to return it
as return value of this function instead of returning 0 all the time? As a
side effect, this would make the function smaller by two lines.

quoted

+
+       return 0;
+}
+
+static int exynos_sata_phy_power_off(struct phy *phy)
+{
+       struct exynos_sata_phy *sata_phy = phy_get_drvdata(phy);
+
+       regmap_update_bits(sata_phy->pmureg, SATAPHY_CONTROL_OFFSET,
+                       EXYNOS5_SATAPHY_PMU_ENABLE, ~EXYNOS_SATA_PHY_EN);

Same here.

quoted

+
+       return 0;
+}
+
+static int exynos_sata_phy_init(struct phy *phy)
+{
+       u32 val = 0;
+       int ret = 0;
+       u8 buf[] = { 0x3A, 0x0B };
+       struct exynos_sata_phy *sata_phy = phy_get_drvdata(phy);
+
+       regmap_update_bits(sata_phy->pmureg, SATAPHY_CONTROL_OFFSET,
+                       EXYNOS5_SATAPHY_PMU_ENABLE, EXYNOS_SATA_PHY_EN);

regmap_update_bits returns an error code.

quoted

+
+       writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
+
+       val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
+       val |= 0xFF;
+       writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
+
+       val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
+       val |= LINK_RESET;
+       writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
+
+       val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
+       val |= RESET_CMN_RST_N;
+       writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
+
+       val = readl(sata_phy->regs + EXYNOS5_SATA_PHSATA_CTRLM);
+       val &= ~PHCTRLM_REF_RATE;
+       writel(val, sata_phy->regs + EXYNOS5_SATA_PHSATA_CTRLM);
+
+       /* High speed enable for Gen3 */
+       val = readl(sata_phy->regs + EXYNOS5_SATA_PHSATA_CTRLM);
+       val |= PHCTRLM_HIGH_SPEED;
+       writel(val, sata_phy->regs + EXYNOS5_SATA_PHSATA_CTRLM);
+
+       val = readl(sata_phy->regs + EXYNOS5_SATA_CTRL0);
+       val |= CTRL0_P0_PHY_CALIBRATED_SEL | CTRL0_P0_PHY_CALIBRATED;
+       writel(val, sata_phy->regs + EXYNOS5_SATA_CTRL0);
+
+       val = readl(sata_phy->regs + EXYNOS5_SATA_MODE0);
+       val |= SATA_SPD_GEN3;
+       writel(val, sata_phy->regs + EXYNOS5_SATA_MODE0);
+
+       ret = i2c_master_send(sata_phy->client, buf, sizeof(buf));
+       if (ret < 0)
+               return -ENXIO;

Wouldn't it be better to return the same error code as i2c_master_send
returned?

quoted

+
+       /* release cmu reset */
+       val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
+       val &= ~RESET_CMN_RST_N;
+       writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
+
+       val = readl(sata_phy->regs + EXYNOS5_SATA_RESET);
+       val |= RESET_CMN_RST_N;
+       writel(val, sata_phy->regs + EXYNOS5_SATA_RESET);
+
+       return (wait_for_reg_status(sata_phy->regs,
EXYNOS5_SATA_PHSATA_STATM,
+               PHSTATM_PLL_LOCKED, 1)) ? 0 : -EINVAL;
+

nit: Stray blank line.

Also it might be more readable after making wait_for_reg_status() return an
integer error code (0 and e.g. -EFAULT) and rewriting the last line to:

        ret = wait_for_reg_status(sata_phy->regs,
                                        EXYNOS5_SATA_PHSATA_STATM,
                                        PHSTATM_PLL_LOCKED, 1);
        if (ret < 0)
                dev_err(&sata_phy->client->dev,
                        "PHY PLL locking failed\n");

        return ret;

By the way, isn't this initialization really needed whenever the PHY is
powered on?

quoted

+}
+
+static struct phy_ops exynos_sata_phy_ops = {
+       .init           = exynos_sata_phy_init,
+       .power_on       = exynos_sata_phy_power_on,
+       .power_off      = exynos_sata_phy_power_off,
+       .owner          = THIS_MODULE,
+};
+
+static int exynos_sata_phy_probe(struct platform_device *pdev)
+{
+       struct exynos_sata_phy *sata_phy;
+       struct device *dev = &pdev->dev;
+       struct resource *res;
+       struct phy_provider *phy_provider;
+       struct device_node *node;
+       int ret = 0;
+
+       sata_phy = devm_kzalloc(dev, sizeof(*sata_phy), GFP_KERNEL);
+       if (!sata_phy)
+               return -ENOMEM;
+
+       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+       sata_phy->regs = devm_ioremap_resource(dev, res);
+       if (IS_ERR(sata_phy->regs))
+               return PTR_ERR(sata_phy->regs);
+
+       sata_phy->pmureg = syscon_regmap_lookup_by_phandle(dev->of_node,
+                                       "samsung,syscon-phandle");

pmureg is defined as (void __iomem *) in struct exynos_sata_phy, but
syscon_regmap_lookup_by_phandle() returns (struct regmap *). Moreover it
does not return NULL on error, but rather ERR_PTR(). Please correct this.

quoted

+       if (!sata_phy->pmureg) {
+               dev_err(dev, "syscon regmap lookup failed.\n");
+               return PTR_ERR(sata_phy->pmureg);
+       }
+
+       node = of_parse_phandle(dev->of_node,
+                       "samsung,exynos-sataphy-i2c-phandle", 0);
+       if (!node)
+               return -ENODEV;

An error here means that a required DT property was not specified or was
specified incorrectly. IMHO -EINVAL would be better here.

quoted

+
+       sata_phy->client = of_find_i2c_device_by_node(node);
+       if (!sata_phy->client)
+               return -EPROBE_DEFER;
+
+       dev_set_drvdata(dev, sata_phy);
+
+       sata_phy->phyclk = devm_clk_get(dev, "sata_phyctrl");
+       if (IS_ERR(sata_phy->phyclk)) {
+               dev_err(dev, "failed to get clk for PHY\n");
+               return PTR_ERR(sata_phy->phyclk);
+       }
+
+       ret = clk_prepare_enable(sata_phy->phyclk);
+       if (ret < 0) {
+               dev_err(dev, "failed to enable source clk\n");
+               return ret;
+       }
+
+       sata_phy->phy = devm_phy_create(dev, &exynos_sata_phy_ops, NULL);
+       if (IS_ERR(sata_phy->phy)) {
+               clk_disable_unprepare(sata_phy->phyclk);
+               dev_err(dev, "failed to create PHY\n");
+               return PTR_ERR(sata_phy->phy);
+       }
+
+       phy_set_drvdata(sata_phy->phy, sata_phy);
+
+       phy_provider = devm_of_phy_provider_register(dev,
+                                       of_phy_simple_xlate);
+       if (IS_ERR(phy_provider)) {
+               clk_disable_unprepare(sata_phy->phyclk);
+               return PTR_ERR(phy_provider);
+       }
+
+       return 0;
+}
+
+static const struct of_device_id exynos_sata_phy_of_match[] = {
+       { .compatible = "samsung,exynos5250-sata-phy" },
+       { },
+};
+MODULE_DEVICE_TABLE(of, exynos_sata_phy_of_match);
+
+static struct platform_driver exynos_sata_phy_driver = {
+       .probe  = exynos_sata_phy_probe,

If this driver can be compiled as module, don't you also need remove?

I tried this and found as such there is no resources hold by this
driver to handle in remove case.
This driver is used by ahci_platform driver and when load
phy-exynos5250-sata,driver usage count is 1.
so if we unload ahci_platform driver first and then
phy-exynos5250-sata.ko it cleanely unload this module.

Best regards,
Tomasz