--- /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 / staging / wigyori.git / blobdiff