+++ /dev/null
-From ffbb6cc14b8fb1876b249048284a5fe30f48c693 Mon Sep 17 00:00:00 2001
-From: Annaliese McDermond <nh6z@nh6z.net>
-Date: Sat, 8 Jun 2019 10:14:43 -0700
-Subject: [PATCH] i2c: bcm2835: Model Divider in CCF
-
-Commit bebff81fb8b9216eb4fba22cf910553621ae3477 upstream.
-
-Model the I2C bus clock divider as a part of the Core Clock Framework.
-Primarily this removes the clk_get_rate() call from each transfer.
-This call causes problems for slave drivers that themselves have
-internal clock components that are controlled by an I2C interface.
-When the slave's internal clock component is prepared, the prepare
-lock is obtained, and it makes calls to the I2C subsystem to
-command the hardware to activate the clock. In order to perform
-the I2C transfer, this driver sets the divider, which requires
-it to get the parent clock rate, which it does with clk_get_rate().
-Unfortunately, this function will try to take the clock prepare
-lock, which is already held by the slave's internal clock calls
-creating a deadlock.
-
-Modeling the divider in the CCF natively removes this dependency
-and the divider value is only set upon changing the bus clock
-frequency or changes in the parent clock that cascade down to this
-divisor. This obviates the need to set the divider with every
-transfer and avoids the deadlock described above. It also should
-provide better clock debugging and save a few cycles on each
-transfer due to not having to recalcuate the divider value.
-
-Signed-off-by: Annaliese McDermond <nh6z@nh6z.net>
-Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
-Reviewed-by: Eric Anholt <eric@anholt.net>
-Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
----
- drivers/i2c/busses/i2c-bcm2835.c | 145 ++++++++++++++++++++++++-------
- 1 file changed, 114 insertions(+), 31 deletions(-)
-
---- a/drivers/i2c/busses/i2c-bcm2835.c
-+++ b/drivers/i2c/busses/i2c-bcm2835.c
-@@ -12,6 +12,8 @@
- */
-
- #include <linux/clk.h>
-+#include <linux/clkdev.h>
-+#include <linux/clk-provider.h>
- #include <linux/completion.h>
- #include <linux/err.h>
- #include <linux/i2c.h>
-@@ -71,9 +73,7 @@ struct bcm2835_debug {
- struct bcm2835_i2c_dev {
- struct device *dev;
- void __iomem *regs;
-- struct clk *clk;
- int irq;
-- u32 bus_clk_rate;
- struct i2c_adapter adapter;
- struct completion completion;
- struct i2c_msg *curr_msg;
-@@ -164,12 +164,17 @@ static inline u32 bcm2835_i2c_readl(stru
- return readl(i2c_dev->regs + reg);
- }
-
--static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev)
-+#define to_clk_bcm2835_i2c(_hw) container_of(_hw, struct clk_bcm2835_i2c, hw)
-+struct clk_bcm2835_i2c {
-+ struct clk_hw hw;
-+ struct bcm2835_i2c_dev *i2c_dev;
-+};
-+
-+static int clk_bcm2835_i2c_calc_divider(unsigned long rate,
-+ unsigned long parent_rate)
- {
-- u32 divider, redl, fedl;
-+ u32 divider = DIV_ROUND_UP(parent_rate, rate);
-
-- divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk),
-- i2c_dev->bus_clk_rate);
- /*
- * Per the datasheet, the register is always interpreted as an even
- * number, by rounding down. In other words, the LSB is ignored. So,
-@@ -178,12 +183,23 @@ static int bcm2835_i2c_set_divider(struc
- if (divider & 1)
- divider++;
- if ((divider < BCM2835_I2C_CDIV_MIN) ||
-- (divider > BCM2835_I2C_CDIV_MAX)) {
-- dev_err_ratelimited(i2c_dev->dev, "Invalid clock-frequency\n");
-+ (divider > BCM2835_I2C_CDIV_MAX))
- return -EINVAL;
-- }
-
-- bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
-+ return divider;
-+}
-+
-+static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate,
-+ unsigned long parent_rate)
-+{
-+ struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
-+ u32 redl, fedl;
-+ u32 divider = clk_bcm2835_i2c_calc_divider(rate, parent_rate);
-+
-+ if (divider == -EINVAL)
-+ return -EINVAL;
-+
-+ bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DIV, divider);
-
- /*
- * Number of core clocks to wait after falling edge before
-@@ -198,12 +214,62 @@ static int bcm2835_i2c_set_divider(struc
- */
- redl = max(divider / 4, 1u);
-
-- bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DEL,
-+ bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DEL,
- (fedl << BCM2835_I2C_FEDL_SHIFT) |
- (redl << BCM2835_I2C_REDL_SHIFT));
- return 0;
- }
-
-+static long clk_bcm2835_i2c_round_rate(struct clk_hw *hw, unsigned long rate,
-+ unsigned long *parent_rate)
-+{
-+ u32 divider = clk_bcm2835_i2c_calc_divider(rate, *parent_rate);
-+
-+ return DIV_ROUND_UP(*parent_rate, divider);
-+}
-+
-+static unsigned long clk_bcm2835_i2c_recalc_rate(struct clk_hw *hw,
-+ unsigned long parent_rate)
-+{
-+ struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
-+ u32 divider = bcm2835_i2c_readl(div->i2c_dev, BCM2835_I2C_DIV);
-+
-+ return DIV_ROUND_UP(parent_rate, divider);
-+}
-+
-+static const struct clk_ops clk_bcm2835_i2c_ops = {
-+ .set_rate = clk_bcm2835_i2c_set_rate,
-+ .round_rate = clk_bcm2835_i2c_round_rate,
-+ .recalc_rate = clk_bcm2835_i2c_recalc_rate,
-+};
-+
-+static struct clk *bcm2835_i2c_register_div(struct device *dev,
-+ const char *mclk_name,
-+ struct bcm2835_i2c_dev *i2c_dev)
-+{
-+ struct clk_init_data init;
-+ struct clk_bcm2835_i2c *priv;
-+ char name[32];
-+
-+ snprintf(name, sizeof(name), "%s_div", dev_name(dev));
-+
-+ init.ops = &clk_bcm2835_i2c_ops;
-+ init.name = name;
-+ init.parent_names = (const char* []) { mclk_name };
-+ init.num_parents = 1;
-+ init.flags = 0;
-+
-+ priv = devm_kzalloc(dev, sizeof(struct clk_bcm2835_i2c), GFP_KERNEL);
-+ if (priv == NULL)
-+ return ERR_PTR(-ENOMEM);
-+
-+ priv->hw.init = &init;
-+ priv->i2c_dev = i2c_dev;
-+
-+ clk_hw_register_clkdev(&priv->hw, "div", dev_name(dev));
-+ return devm_clk_register(dev, &priv->hw);
-+}
-+
- static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
- {
- u32 val;
-@@ -363,7 +429,7 @@ static int bcm2835_i2c_xfer(struct i2c_a
- {
- struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
- unsigned long time_left;
-- int i, ret;
-+ int i;
-
- if (debug)
- i2c_dev->debug_num_msgs = num;
-@@ -379,10 +445,6 @@ static int bcm2835_i2c_xfer(struct i2c_a
- return -EOPNOTSUPP;
- }
-
-- ret = bcm2835_i2c_set_divider(i2c_dev);
-- if (ret)
-- return ret;
--
- i2c_dev->curr_msg = msgs;
- i2c_dev->num_msgs = num;
- reinit_completion(&i2c_dev->completion);
-@@ -443,6 +505,9 @@ static int bcm2835_i2c_probe(struct plat
- struct resource *mem, *irq;
- int ret;
- struct i2c_adapter *adap;
-+ const char *mclk_name;
-+ struct clk *bus_clk;
-+ u32 bus_clk_rate;
-
- i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
- if (!i2c_dev)
-@@ -456,21 +521,6 @@ static int bcm2835_i2c_probe(struct plat
- if (IS_ERR(i2c_dev->regs))
- return PTR_ERR(i2c_dev->regs);
-
-- i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
-- if (IS_ERR(i2c_dev->clk)) {
-- if (PTR_ERR(i2c_dev->clk) != -EPROBE_DEFER)
-- dev_err(&pdev->dev, "Could not get clock\n");
-- return PTR_ERR(i2c_dev->clk);
-- }
--
-- ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
-- &i2c_dev->bus_clk_rate);
-- if (ret < 0) {
-- dev_warn(&pdev->dev,
-- "Could not read clock-frequency property\n");
-- i2c_dev->bus_clk_rate = 100000;
-- }
--
- irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
- if (!irq) {
- dev_err(&pdev->dev, "No IRQ resource\n");
-@@ -485,6 +535,35 @@ static int bcm2835_i2c_probe(struct plat
- return -ENODEV;
- }
-
-+ mclk_name = of_clk_get_parent_name(pdev->dev.of_node, 0);
-+
-+ bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk_name, i2c_dev);
-+
-+ if (IS_ERR(bus_clk)) {
-+ dev_err(&pdev->dev, "Could not register clock\n");
-+ return PTR_ERR(bus_clk);
-+ }
-+
-+ ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
-+ &bus_clk_rate);
-+ if (ret < 0) {
-+ dev_warn(&pdev->dev,
-+ "Could not read clock-frequency property\n");
-+ bus_clk_rate = 100000;
-+ }
-+
-+ ret = clk_set_rate_exclusive(bus_clk, bus_clk_rate);
-+ if (ret < 0) {
-+ dev_err(&pdev->dev, "Could not set clock frequency\n");
-+ return ret;
-+ }
-+
-+ ret = clk_prepare_enable(bus_clk);
-+ if (ret) {
-+ dev_err(&pdev->dev, "Couldn't prepare clock");
-+ return ret;
-+ }
-+
- adap = &i2c_dev->adapter;
- i2c_set_adapdata(adap, i2c_dev);
- adap->owner = THIS_MODULE;
-@@ -507,6 +586,10 @@ static int bcm2835_i2c_probe(struct plat
- static int bcm2835_i2c_remove(struct platform_device *pdev)
- {
- struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
-+ struct clk *bus_clk = devm_clk_get(i2c_dev->dev, "div");
-+
-+ clk_rate_exclusive_put(bus_clk);
-+ clk_disable_unprepare(bus_clk);
-
- free_irq(i2c_dev->irq, i2c_dev);
- i2c_del_adapter(&i2c_dev->adapter);
projects / openwrt / openwrt.git / blobdiff