Re: [PATCH V5 3/5] tty: serial: meson: Using the common clock code describe.
From: Yu Tu
Date: Mon Jan 10 2022 - 22:14:00 EST
Hi Jiri,
Thank you very much for your reply.
On 2022/1/10 20:11, Jiri Slaby wrote:
[ EXTERNAL EMAIL ]
Hi,
"Subject: Using the common clock code describe."
Please reformulate that ^^^ -- I cannot make any sense of it. And avoid
adding a period to the subject. PLease see others' commit logs.
I will correct this in the next version.
On 10. 01. 22, 11:42, Yu Tu wrote:
Using the common Clock code to describe the UART baud rate clock
makes it easier for the UART driver to be compatible with the
baud rate requirements of the UART IP on different meson chips.
Signed-off-by: Yu Tu <yu.tu@xxxxxxxxxxx>
---
drivers/tty/serial/meson_uart.c | 224 +++++++++++++++++++++++---------
1 file changed, 163 insertions(+), 61 deletions(-)
diff --git a/drivers/tty/serial/meson_uart.c
b/drivers/tty/serial/meson_uart.c
index 7570958d010c..1004fd0b0c9e 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -6,6 +6,7 @@
*/
#include <linux/clk.h>
+#include <linux/clk-provider.h>
#include <linux/console.h>
#include <linux/delay.h>
#include <linux/init.h>
@@ -65,9 +66,7 @@
#define AML_UART_RECV_IRQ(c) ((c) & 0xff)
/* AML_UART_REG5 bits */
-#define AML_UART_BAUD_MASK 0x7fffff
#define AML_UART_BAUD_USE BIT(23)
-#define AML_UART_BAUD_XTAL BIT(24)
#define AML_UART_PORT_NUM 12
#define AML_UART_PORT_OFFSET 6
@@ -76,6 +75,13 @@
#define AML_UART_POLL_USEC 5
#define AML_UART_TIMEOUT_USEC 10000
+struct meson_uart_data {
+ struct uart_port port;
+ struct clk *pclk;
+ struct clk *baud_clk;
+ bool use_xtal_clk;
+};
+
static struct uart_driver meson_uart_driver;
static struct uart_port *meson_ports[AML_UART_PORT_NUM];
@@ -268,14 +274,11 @@ static void meson_uart_reset(struct uart_port
*port)
static int meson_uart_startup(struct uart_port *port)
{
u32 val;
- int ret = 0;
+ int ret;
- val = readl(port->membase + AML_UART_CONTROL);
- val |= AML_UART_CLEAR_ERR;
- writel(val, port->membase + AML_UART_CONTROL);
- val &= ~AML_UART_CLEAR_ERR;
- writel(val, port->membase + AML_UART_CONTROL);
+ meson_uart_reset(port);
Why is this OK? We didn't use to reset it.
This change simply optimizes the code. Because the meson_uart_reset
function has implemented the control logic.
And why is this not done in a separate patch?
I will consider merging with the previous patch as a patch.
+ val = readl(port->membase + AML_UART_CONTROL);
val |= (AML_UART_RX_EN | AML_UART_TX_EN);
writel(val, port->membase + AML_UART_CONTROL);
@@ -293,19 +296,17 @@ static int meson_uart_startup(struct uart_port
*port)
static void meson_uart_change_speed(struct uart_port *port, unsigned
long baud)
{
+ struct meson_uart_data *private_data = port->private_data;
u32 val;
while (!meson_uart_tx_empty(port))
cpu_relax();
- if (port->uartclk == 24000000) {
- val = ((port->uartclk / 3) / baud) - 1;
- val |= AML_UART_BAUD_XTAL;
- } else {
- val = ((port->uartclk * 10 / (baud * 4) + 5) / 10) - 1;
- }
+ val = readl(port->membase + AML_UART_REG5);
val |= AML_UART_BAUD_USE;
writel(val, port->membase + AML_UART_REG5);
+
+ clk_set_rate(private_data->baud_clk, baud);
}
static void meson_uart_set_termios(struct uart_port *port,
@@ -395,11 +396,27 @@ static int meson_uart_verify_port(struct
uart_port *port,
static void meson_uart_release_port(struct uart_port *port)
{
- /* nothing to do */
+ struct meson_uart_data *private_data = port->private_data;
+
+ clk_disable_unprepare(private_data->baud_clk);
+ clk_disable_unprepare(private_data->pclk);
}
static int meson_uart_request_port(struct uart_port *port)
{
+ struct meson_uart_data *private_data = port->private_data;
+ int ret;
+
+ ret = clk_prepare_enable(private_data->pclk);
+ if (ret)
+ return ret;
+
+ ret = clk_prepare_enable(private_data->baud_clk);
+ if (ret) {
+ clk_disable_unprepare(private_data->pclk);
+ return ret;
+ }
+
return 0;
}
@@ -629,55 +646,105 @@ static struct uart_driver meson_uart_driver = {
.cons = MESON_SERIAL_CONSOLE,
};
-static inline struct clk *meson_uart_probe_clock(struct device *dev,
- const char *id)
+#define CLK_NAME(name) \
+({\
+ char clk_name[32];\
+ snprintf(clk_name, sizeof(clk_name), "%s#%s",
dev_name(port->dev), #name);\
+ clk_name;\
+})
This is cryptic and duplicates the variable on the stack. Why not expand
the macro and delete it then?
I've overdone it. I'll move it to the meson_uart_probe_clocks function
as you suggested and delete it.
+
+static struct clk_div_table xtal_div_table[] = {
+ { 0, 3 },
An extra space here and there:
+ { 1, 1 },
+ { 2, 2 },
+ { 3, 2 },
+};
+
Sorry, stupid mistake. I will correct.
+static int meson_uart_probe_clocks(struct uart_port *port)
{
- struct clk *clk = NULL;
- int ret;
+ struct meson_uart_data *private_data = port->private_data;
+ struct clk *clk_baud, *clk_xtal;
+ struct clk_hw *hw;
+ struct clk_parent_data use_xtal_mux_parents[2] = {
+ { .index = -1, },
+ { .index = -1, },
+ };
- clk = devm_clk_get(dev, id);
- if (IS_ERR(clk))
- return clk;
+ private_data->pclk = devm_clk_get(port->dev, "pclk");
+ if (IS_ERR(private_data->pclk))
+ return dev_err_probe(port->dev, PTR_ERR(private_data->pclk),
+ "Failed to get the 'pclk' clock\n");
- ret = clk_prepare_enable(clk);
- if (ret) {
- dev_err(dev, "couldn't enable clk\n");
- return ERR_PTR(ret);
+ clk_baud = devm_clk_get(port->dev, "baud");
+ if (IS_ERR(clk_baud)) {
+ dev_err(port->dev, "Failed to get the 'baud' clock\n");
+ return PTR_ERR(clk_baud);
}
- devm_add_action_or_reset(dev,
- (void(*)(void *))clk_disable_unprepare,
- clk);
-
- return clk;
-}
-
-static int meson_uart_probe_clocks(struct platform_device *pdev,
- struct uart_port *port)
-{
- struct clk *clk_xtal = NULL;
- struct clk *clk_pclk = NULL;
- struct clk *clk_baud = NULL;
-
- clk_pclk = meson_uart_probe_clock(&pdev->dev, "pclk");
- if (IS_ERR(clk_pclk))
- return PTR_ERR(clk_pclk);
-
- clk_xtal = meson_uart_probe_clock(&pdev->dev, "xtal");
+ clk_xtal = devm_clk_get(port->dev, "xtal");
if (IS_ERR(clk_xtal))
- return PTR_ERR(clk_xtal);
-
- clk_baud = meson_uart_probe_clock(&pdev->dev, "baud");
- if (IS_ERR(clk_baud))
- return PTR_ERR(clk_baud);
+ return dev_err_probe(port->dev, PTR_ERR(clk_xtal),
+ "Failed to get the 'xtal' clock\n");
+
+ if (private_data->use_xtal_clk) {
+ hw = devm_clk_hw_register_divider_table(port->dev,
+ CLK_NAME(xtal_div),
+ __clk_get_name(clk_baud),
+ CLK_SET_RATE_NO_REPARENT,
+ port->membase + AML_UART_REG5,
+ 26, 2,
+ CLK_DIVIDER_READ_ONLY,
+ xtal_div_table, NULL);
+ if (IS_ERR(hw))
+ return PTR_ERR(hw);
+
+ use_xtal_mux_parents[1].hw = hw;
+ } else {
+ hw = devm_clk_hw_register_fixed_factor(port->dev,
+ CLK_NAME(clk81_div4),
+ __clk_get_name(clk_baud),
+ CLK_SET_RATE_NO_REPARENT,
+ 1, 4);
+ if (IS_ERR(hw))
+ return PTR_ERR(hw);
+
+ use_xtal_mux_parents[0].hw = hw;
+ }
- port->uartclk = clk_get_rate(clk_baud);
+ hw = __devm_clk_hw_register_mux(port->dev, NULL,
+ CLK_NAME(use_xtal),
+ ARRAY_SIZE(use_xtal_mux_parents),
+ NULL, NULL,
+ use_xtal_mux_parents,
+ CLK_SET_RATE_PARENT,
+ port->membase + AML_UART_REG5,
+ 24, 0x1,
+ CLK_MUX_READ_ONLY,
+ NULL, NULL);
+ if (IS_ERR(hw))
+ return PTR_ERR(hw);
+
+ port->uartclk = clk_hw_get_rate(hw);
+
+ hw = devm_clk_hw_register_divider(port->dev,
+ CLK_NAME(baud_div),
+ clk_hw_get_name(hw),
+ CLK_SET_RATE_PARENT,
+ port->membase + AML_UART_REG5,
+ 0, 23,
+ CLK_DIVIDER_ROUND_CLOSEST,
+ NULL);
+ if (IS_ERR(hw))
+ return PTR_ERR(hw);
+
+ private_data->baud_clk = clk_hw_get_clk(hw, "baud_rate");
return 0;
}