diff mbox series

[V6,3/5] tty: serial: meson: Describes the calculation of the UART baud rate clock using a clock frame

Message ID 20220118030911.12815-4-yu.tu@amlogic.com (mailing list archive)
State Superseded
Headers show
Series Use CCF to describe the UART baud rate clock | expand

Commit Message

Yu Tu Jan. 18, 2022, 3:09 a.m. UTC
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@amlogic.com>
---
 drivers/tty/serial/meson_uart.c | 195 +++++++++++++++++++++++---------
 1 file changed, 142 insertions(+), 53 deletions(-)

Comments

Jiri Slaby Jan. 18, 2022, 9:39 a.m. UTC | #1
On 18. 01. 22, 4:09, 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.
...
> --- a/drivers/tty/serial/meson_uart.c
> +++ b/drivers/tty/serial/meson_uart.c
...
> @@ -629,57 +640,105 @@ 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)
> -{
> -	struct clk *clk = NULL;
> -	int ret;
> -
> -	clk = devm_clk_get(dev, id);
> -	if (IS_ERR(clk))
> -		return clk;
> -
> -	ret = clk_prepare_enable(clk);
> -	if (ret) {
> -		dev_err(dev, "couldn't enable clk\n");
> -		return ERR_PTR(ret);
> -	}
> -
> -	devm_add_action_or_reset(dev,
> -			(void(*)(void *))clk_disable_unprepare,
> -			clk);
> -
> -	return clk;
> -}
> +static struct clk_div_table xtal_div_table[] = {

This can be const, right?

> +	{0, 3},
> +	{1, 1},
> +	{2, 2},
> +	{3, 2},

Not sure if you didn't remove too much whitespace. I think it should be 
like: "{ 0, 3 },". But I actually don't care, it's a minor thing.

I cannot comment on the rest (clk and OF part) as my knowledge is pretty 
limited there. Leaving up to others.

thanks,
Yu Tu Jan. 19, 2022, 6 a.m. UTC | #2
Hi Jiri,
	Thank you very much for your patient reply.I learned a lot from your 
response.

On 2022/1/18 17:39, Jiri Slaby wrote:
> [ EXTERNAL EMAIL ]
> 
> On 18. 01. 22, 4:09, 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.
> ...
>> --- a/drivers/tty/serial/meson_uart.c
>> +++ b/drivers/tty/serial/meson_uart.c
> ...
>> @@ -629,57 +640,105 @@ 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)
>> -{
>> -    struct clk *clk = NULL;
>> -    int ret;
>> -
>> -    clk = devm_clk_get(dev, id);
>> -    if (IS_ERR(clk))
>> -        return clk;
>> -
>> -    ret = clk_prepare_enable(clk);
>> -    if (ret) {
>> -        dev_err(dev, "couldn't enable clk\n");
>> -        return ERR_PTR(ret);
>> -    }
>> -
>> -    devm_add_action_or_reset(dev,
>> -            (void(*)(void *))clk_disable_unprepare,
>> -            clk);
>> -
>> -    return clk;
>> -}
>> +static struct clk_div_table xtal_div_table[] = {
> 
> This can be const, right?
You are right.
> 
>> +    {0, 3},
>> +    {1, 1},
>> +    {2, 2},
>> +    {3, 2},
> 
> Not sure if you didn't remove too much whitespace. I think it should be 
> like: "{ 0, 3 },". But I actually don't care, it's a minor thing.
> 
Ok, I will correct it if it needs to be changed.
> I cannot comment on the rest (clk and OF part) as my knowledge is pretty 
> limited there. Leaving up to others.
> 
Anyway, thanks for your reply.
> thanks,
Jerome Brunet Jan. 20, 2022, 9:40 p.m. UTC | #3
On Tue 18 Jan 2022 at 11:09, Yu Tu <yu.tu@amlogic.com> 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@amlogic.com>
> ---
>  drivers/tty/serial/meson_uart.c | 195 +++++++++++++++++++++++---------
>  1 file changed, 142 insertions(+), 53 deletions(-)
>
> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
> index 7570958d010c..92fa91c825e6 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 +75,11 @@
>  #define AML_UART_POLL_USEC		5
>  #define AML_UART_TIMEOUT_USEC		10000
>  
> +struct meson_uart_data {
> +	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];
> @@ -293,19 +297,17 @@ 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 +397,20 @@ 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);
>  }
>  
>  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->baud_clk);
> +	if (ret)
> +		return ret;
> +
>  	return 0;
>  }
>  
> @@ -629,57 +640,105 @@ 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)
> -{
> -	struct clk *clk = NULL;
> -	int ret;
> -
> -	clk = devm_clk_get(dev, id);
> -	if (IS_ERR(clk))
> -		return clk;
> -
> -	ret = clk_prepare_enable(clk);
> -	if (ret) {
> -		dev_err(dev, "couldn't enable clk\n");
> -		return ERR_PTR(ret);
> -	}
> -
> -	devm_add_action_or_reset(dev,
> -			(void(*)(void *))clk_disable_unprepare,
> -			clk);
> -
> -	return clk;
> -}
> +static struct clk_div_table xtal_div_table[] = {
> +	{0, 3},
> +	{1, 1},
> +	{2, 2},
> +	{3, 2},
> +};
>  
> -static int meson_uart_probe_clocks(struct platform_device *pdev,
> -				   struct uart_port *port)
> +static int meson_uart_probe_clocks(struct uart_port *port)
>  {
> -	struct clk *clk_xtal = NULL;
> -	struct clk *clk_pclk = NULL;
> -	struct clk *clk_baud = NULL;
> +	struct meson_uart_data *private_data = port->private_data;
> +	struct clk *clk_baud, *clk_xtal;
> +	struct clk_hw *hw;
> +	char clk_name[32];
> +	struct clk_parent_data use_xtal_mux_parents[2] = {
> +		{ .index = -1, },
> +		{ .index = -1, },
> +	};

You are using hw pointers later, you don't need to init the index to -1
I think

>  
> -	clk_pclk = meson_uart_probe_clock(&pdev->dev, "pclk");
> -	if (IS_ERR(clk_pclk))
> -		return PTR_ERR(clk_pclk);
> +	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);
> +	}
>  
> -	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) {
> +		snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
> +			 "xtal_div");
> +		hw = devm_clk_hw_register_divider_table(port->dev,
> +							clk_name,
> +							__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 {
> +		snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
> +			 "clk81_div4");
> +		hw = devm_clk_hw_register_fixed_factor(port->dev,
> +						       clk_name,
> +						       __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;
> +	}

The above is still wrong.

use_xtal_mux_parents initialize both parent to nothing
And you init the parent in the conditional above.
It is means only one path is actually set instead of both.

The mux always has 2 sources - Both should be set regardless of the HW version
You just add
* /4 on path 0 on legacy SoC
* the funky divider on path 1 on newer SoC.

>  
> -	port->uartclk = clk_get_rate(clk_baud);
> +	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
> +		 "use_xtal");
> +	hw = __devm_clk_hw_register_mux(port->dev, NULL,
> +					clk_name,
> +					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);
> +
> +	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
> +		 "baud_div");
> +	hw = devm_clk_hw_register_divider(port->dev,
> +					  clk_name,
> +					  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 = hw->clk;
>  
>  	return 0;
>  }
>  
>  static int meson_uart_probe(struct platform_device *pdev)
>  {
> +	struct meson_uart_data *private_data;
>  	struct resource *res_mem;
>  	struct uart_port *port;
> +	struct clk *pclk;
>  	u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */
>  	int ret = 0;
>  	int irq;
> @@ -705,6 +764,15 @@ static int meson_uart_probe(struct platform_device *pdev)
>  	if (!res_mem)
>  		return -ENODEV;
>  
> +	pclk = devm_clk_get(&pdev->dev, "pclk");
> +	if (IS_ERR(pclk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(pclk),
> +				     "Failed to get the 'pclk' clock\n");
> +
> +	ret = clk_prepare_enable(pclk);
> +	if (ret)
> +		return ret;
> +

I think this is unbalanced. 

>  	irq = platform_get_irq(pdev, 0);
>  	if (irq < 0)
>  		return irq;
> @@ -724,9 +792,13 @@ static int meson_uart_probe(struct platform_device *pdev)
>  	if (IS_ERR(port->membase))
>  		return PTR_ERR(port->membase);
>  
> -	ret = meson_uart_probe_clocks(pdev, port);
> -	if (ret)
> -		return ret;
> +	private_data = devm_kzalloc(&pdev->dev, sizeof(*private_data),
> +				    GFP_KERNEL);
> +	if (!private_data)
> +		return -ENOMEM;
> +
> +	if (device_get_match_data(&pdev->dev))
> +		private_data->use_xtal_clk = true;
>  
>  	port->iotype = UPIO_MEM;
>  	port->mapbase = res_mem->start;
> @@ -740,6 +812,11 @@ static int meson_uart_probe(struct platform_device *pdev)
>  	port->x_char = 0;
>  	port->ops = &meson_uart_ops;
>  	port->fifosize = fifosize;
> +	port->private_data = private_data;
> +
> +	ret = meson_uart_probe_clocks(port);
> +	if (ret)
> +		return ret;
>  
>  	meson_ports[pdev->id] = port;
>  	platform_set_drvdata(pdev, port);
> @@ -766,10 +843,22 @@ static int meson_uart_remove(struct platform_device *pdev)
>  }
>  
>  static const struct of_device_id meson_uart_dt_match[] = {
> -	{ .compatible = "amlogic,meson6-uart" },
> -	{ .compatible = "amlogic,meson8-uart" },
> -	{ .compatible = "amlogic,meson8b-uart" },
> -	{ .compatible = "amlogic,meson-gx-uart" },
> +	{
> +		.compatible = "amlogic,meson6-uart",
> +		.data = (void *)false,
> +	},
> +	{
> +		.compatible = "amlogic,meson8-uart",
> +		.data = (void *)false,
> +	},
> +	{
> +		.compatible = "amlogic,meson8b-uart",
> +		.data = (void *)false,
> +	},
> +	{
> +		.compatible = "amlogic,meson-gx-uart",
> +		.data = (void *)true,
> +	},
>  	{ /* sentinel */ },
>  };
>  MODULE_DEVICE_TABLE(of, meson_uart_dt_match);
Jerome Brunet Jan. 20, 2022, 9:48 p.m. UTC | #4
On Tue 18 Jan 2022 at 10:39, Jiri Slaby <jirislaby@kernel.org> wrote:

> On 18. 01. 22, 4:09, 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.
> ...
>> --- a/drivers/tty/serial/meson_uart.c
>> +++ b/drivers/tty/serial/meson_uart.c
> ...
>> @@ -629,57 +640,105 @@ 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)
>> -{
>> -	struct clk *clk = NULL;
>> -	int ret;
>> -
>> -	clk = devm_clk_get(dev, id);
>> -	if (IS_ERR(clk))
>> -		return clk;
>> -
>> -	ret = clk_prepare_enable(clk);
>> -	if (ret) {
>> -		dev_err(dev, "couldn't enable clk\n");
>> -		return ERR_PTR(ret);
>> -	}
>> -
>> -	devm_add_action_or_reset(dev,
>> -			(void(*)(void *))clk_disable_unprepare,
>> -			clk);
>> -
>> -	return clk;
>> -}
>> +static struct clk_div_table xtal_div_table[] = {
>
> This can be const, right?
>
>> +	{0, 3},
>> +	{1, 1},
>> +	{2, 2},
>> +	{3, 2},
>
> Not sure if you didn't remove too much whitespace. I think it should be
> like: "{ 0, 3 },". But I actually don't care, it's a minor thing.

Seconds
It worth fixing in the next version

>
> I cannot comment on the rest (clk and OF part) as my knowledge is pretty
> limited there. Leaving up to others.
>
> thanks,
Yu Tu Jan. 21, 2022, 2:51 a.m. UTC | #5
Hi Jerome ,
	Thank you very much for your reply.
	At present, it is found that after using CCF to describe baud rate 
clock, when using stty to change baud rate, the situation will be stuck. 
  If initcall_debug is enabled, the initialization of the UART driver 
takes longer . Shall we discuss this first and change it as you suggest? 
I have replied to Kevin about this question yesterday.
Do you need to discuss it? What should I do next?

On 2022/1/21 5:40, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
> 
> 
> On Tue 18 Jan 2022 at 11:09, Yu Tu <yu.tu@amlogic.com> 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@amlogic.com>
>> ---
>>   drivers/tty/serial/meson_uart.c | 195 +++++++++++++++++++++++---------
>>   1 file changed, 142 insertions(+), 53 deletions(-)
>>
>> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
>> index 7570958d010c..92fa91c825e6 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 +75,11 @@
>>   #define AML_UART_POLL_USEC		5
>>   #define AML_UART_TIMEOUT_USEC		10000
>>   
>> +struct meson_uart_data {
>> +	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];
>> @@ -293,19 +297,17 @@ 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 +397,20 @@ 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);
>>   }
>>   
>>   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->baud_clk);
>> +	if (ret)
>> +		return ret;
>> +
>>   	return 0;
>>   }
>>   
>> @@ -629,57 +640,105 @@ 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)
>> -{
>> -	struct clk *clk = NULL;
>> -	int ret;
>> -
>> -	clk = devm_clk_get(dev, id);
>> -	if (IS_ERR(clk))
>> -		return clk;
>> -
>> -	ret = clk_prepare_enable(clk);
>> -	if (ret) {
>> -		dev_err(dev, "couldn't enable clk\n");
>> -		return ERR_PTR(ret);
>> -	}
>> -
>> -	devm_add_action_or_reset(dev,
>> -			(void(*)(void *))clk_disable_unprepare,
>> -			clk);
>> -
>> -	return clk;
>> -}
>> +static struct clk_div_table xtal_div_table[] = {
>> +	{0, 3},
>> +	{1, 1},
>> +	{2, 2},
>> +	{3, 2},
>> +};
>>   
>> -static int meson_uart_probe_clocks(struct platform_device *pdev,
>> -				   struct uart_port *port)
>> +static int meson_uart_probe_clocks(struct uart_port *port)
>>   {
>> -	struct clk *clk_xtal = NULL;
>> -	struct clk *clk_pclk = NULL;
>> -	struct clk *clk_baud = NULL;
>> +	struct meson_uart_data *private_data = port->private_data;
>> +	struct clk *clk_baud, *clk_xtal;
>> +	struct clk_hw *hw;
>> +	char clk_name[32];
>> +	struct clk_parent_data use_xtal_mux_parents[2] = {
>> +		{ .index = -1, },
>> +		{ .index = -1, },
>> +	};
> 
> You are using hw pointers later, you don't need to init the index to -1
> I think
> 
>>   
>> -	clk_pclk = meson_uart_probe_clock(&pdev->dev, "pclk");
>> -	if (IS_ERR(clk_pclk))
>> -		return PTR_ERR(clk_pclk);
>> +	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);
>> +	}
>>   
>> -	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) {
>> +		snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
>> +			 "xtal_div");
>> +		hw = devm_clk_hw_register_divider_table(port->dev,
>> +							clk_name,
>> +							__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 {
>> +		snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
>> +			 "clk81_div4");
>> +		hw = devm_clk_hw_register_fixed_factor(port->dev,
>> +						       clk_name,
>> +						       __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;
>> +	}
> 
> The above is still wrong.
> 
> use_xtal_mux_parents initialize both parent to nothing
> And you init the parent in the conditional above.
> It is means only one path is actually set instead of both.
> 
> The mux always has 2 sources - Both should be set regardless of the HW version
> You just add
> * /4 on path 0 on legacy SoC
> * the funky divider on path 1 on newer SoC.
> 
>>   
>> -	port->uartclk = clk_get_rate(clk_baud);
>> +	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
>> +		 "use_xtal");
>> +	hw = __devm_clk_hw_register_mux(port->dev, NULL,
>> +					clk_name,
>> +					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);
>> +
>> +	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
>> +		 "baud_div");
>> +	hw = devm_clk_hw_register_divider(port->dev,
>> +					  clk_name,
>> +					  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 = hw->clk;
>>   
>>   	return 0;
>>   }
>>   
>>   static int meson_uart_probe(struct platform_device *pdev)
>>   {
>> +	struct meson_uart_data *private_data;
>>   	struct resource *res_mem;
>>   	struct uart_port *port;
>> +	struct clk *pclk;
>>   	u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */
>>   	int ret = 0;
>>   	int irq;
>> @@ -705,6 +764,15 @@ static int meson_uart_probe(struct platform_device *pdev)
>>   	if (!res_mem)
>>   		return -ENODEV;
>>   
>> +	pclk = devm_clk_get(&pdev->dev, "pclk");
>> +	if (IS_ERR(pclk))
>> +		return dev_err_probe(&pdev->dev, PTR_ERR(pclk),
>> +				     "Failed to get the 'pclk' clock\n");
>> +
>> +	ret = clk_prepare_enable(pclk);
>> +	if (ret)
>> +		return ret;
>> +
> 
> I think this is unbalanced.
> 
>>   	irq = platform_get_irq(pdev, 0);
>>   	if (irq < 0)
>>   		return irq;
>> @@ -724,9 +792,13 @@ static int meson_uart_probe(struct platform_device *pdev)
>>   	if (IS_ERR(port->membase))
>>   		return PTR_ERR(port->membase);
>>   
>> -	ret = meson_uart_probe_clocks(pdev, port);
>> -	if (ret)
>> -		return ret;
>> +	private_data = devm_kzalloc(&pdev->dev, sizeof(*private_data),
>> +				    GFP_KERNEL);
>> +	if (!private_data)
>> +		return -ENOMEM;
>> +
>> +	if (device_get_match_data(&pdev->dev))
>> +		private_data->use_xtal_clk = true;
>>   
>>   	port->iotype = UPIO_MEM;
>>   	port->mapbase = res_mem->start;
>> @@ -740,6 +812,11 @@ static int meson_uart_probe(struct platform_device *pdev)
>>   	port->x_char = 0;
>>   	port->ops = &meson_uart_ops;
>>   	port->fifosize = fifosize;
>> +	port->private_data = private_data;
>> +
>> +	ret = meson_uart_probe_clocks(port);
>> +	if (ret)
>> +		return ret;
>>   
>>   	meson_ports[pdev->id] = port;
>>   	platform_set_drvdata(pdev, port);
>> @@ -766,10 +843,22 @@ static int meson_uart_remove(struct platform_device *pdev)
>>   }
>>   
>>   static const struct of_device_id meson_uart_dt_match[] = {
>> -	{ .compatible = "amlogic,meson6-uart" },
>> -	{ .compatible = "amlogic,meson8-uart" },
>> -	{ .compatible = "amlogic,meson8b-uart" },
>> -	{ .compatible = "amlogic,meson-gx-uart" },
>> +	{
>> +		.compatible = "amlogic,meson6-uart",
>> +		.data = (void *)false,
>> +	},
>> +	{
>> +		.compatible = "amlogic,meson8-uart",
>> +		.data = (void *)false,
>> +	},
>> +	{
>> +		.compatible = "amlogic,meson8b-uart",
>> +		.data = (void *)false,
>> +	},
>> +	{
>> +		.compatible = "amlogic,meson-gx-uart",
>> +		.data = (void *)true,
>> +	},
>>   	{ /* sentinel */ },
>>   };
>>   MODULE_DEVICE_TABLE(of, meson_uart_dt_match);
>
Yu Tu Feb. 21, 2022, 8:26 a.m. UTC | #6
On 2022/1/21 5:48, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
> 
> 
> On Tue 18 Jan 2022 at 10:39, Jiri Slaby <jirislaby@kernel.org> wrote:
> 
>> On 18. 01. 22, 4:09, 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.
>> ...
>>> --- a/drivers/tty/serial/meson_uart.c
>>> +++ b/drivers/tty/serial/meson_uart.c
>> ...
>>> @@ -629,57 +640,105 @@ 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)
>>> -{
>>> -	struct clk *clk = NULL;
>>> -	int ret;
>>> -
>>> -	clk = devm_clk_get(dev, id);
>>> -	if (IS_ERR(clk))
>>> -		return clk;
>>> -
>>> -	ret = clk_prepare_enable(clk);
>>> -	if (ret) {
>>> -		dev_err(dev, "couldn't enable clk\n");
>>> -		return ERR_PTR(ret);
>>> -	}
>>> -
>>> -	devm_add_action_or_reset(dev,
>>> -			(void(*)(void *))clk_disable_unprepare,
>>> -			clk);
>>> -
>>> -	return clk;
>>> -}
>>> +static struct clk_div_table xtal_div_table[] = {
>>
>> This can be const, right?
>>
>>> +	{0, 3},
>>> +	{1, 1},
>>> +	{2, 2},
>>> +	{3, 2},
>>
>> Not sure if you didn't remove too much whitespace. I think it should be
>> like: "{ 0, 3 },". But I actually don't care, it's a minor thing.
> 
> Seconds
> It worth fixing in the next version
> 
I will correct in a version.
>>
>> I cannot comment on the rest (clk and OF part) as my knowledge is pretty
>> limited there. Leaving up to others.
>>
>> thanks,
>
Yu Tu Feb. 21, 2022, 8:52 a.m. UTC | #7
Hi Jerome,
     Thank you very much for your reply. At present, the problem of 
switching UART baud rate stuck has been solved. I'm ready to send the 
next edition. However, I still don't understand your suggestion and need 
to communicate with you.

On 2022/1/21 5:40, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
> 
> 
> On Tue 18 Jan 2022 at 11:09, Yu Tu <yu.tu@amlogic.com> 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@amlogic.com>
>> ---
>>   drivers/tty/serial/meson_uart.c | 195 +++++++++++++++++++++++---------
>>   1 file changed, 142 insertions(+), 53 deletions(-)
>>
>> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
>> index 7570958d010c..92fa91c825e6 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 +75,11 @@
>>   #define AML_UART_POLL_USEC		5
>>   #define AML_UART_TIMEOUT_USEC		10000
>>   
>> +struct meson_uart_data {
>> +	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];
>> @@ -293,19 +297,17 @@ 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 +397,20 @@ 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);
>>   }
>>   
>>   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->baud_clk);
>> +	if (ret)
>> +		return ret;
>> +
>>   	return 0;
>>   }
>>   
>> @@ -629,57 +640,105 @@ 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)
>> -{
>> -	struct clk *clk = NULL;
>> -	int ret;
>> -
>> -	clk = devm_clk_get(dev, id);
>> -	if (IS_ERR(clk))
>> -		return clk;
>> -
>> -	ret = clk_prepare_enable(clk);
>> -	if (ret) {
>> -		dev_err(dev, "couldn't enable clk\n");
>> -		return ERR_PTR(ret);
>> -	}
>> -
>> -	devm_add_action_or_reset(dev,
>> -			(void(*)(void *))clk_disable_unprepare,
>> -			clk);
>> -
>> -	return clk;
>> -}
>> +static struct clk_div_table xtal_div_table[] = {
>> +	{0, 3},
>> +	{1, 1},
>> +	{2, 2},
>> +	{3, 2},
>> +};
>>   
>> -static int meson_uart_probe_clocks(struct platform_device *pdev,
>> -				   struct uart_port *port)
>> +static int meson_uart_probe_clocks(struct uart_port *port)
>>   {
>> -	struct clk *clk_xtal = NULL;
>> -	struct clk *clk_pclk = NULL;
>> -	struct clk *clk_baud = NULL;
>> +	struct meson_uart_data *private_data = port->private_data;
>> +	struct clk *clk_baud, *clk_xtal;
>> +	struct clk_hw *hw;
>> +	char clk_name[32];
>> +	struct clk_parent_data use_xtal_mux_parents[2] = {
>> +		{ .index = -1, },
>> +		{ .index = -1, },
>> +	};
> 
> You are using hw pointers later, you don't need to init the index to -1
> I think
> 
I'm going to delete them in the next version.
like: struct clk_parent_data use_xtal_mux_parents[2] = { };
>>   
>> -	clk_pclk = meson_uart_probe_clock(&pdev->dev, "pclk");
>> -	if (IS_ERR(clk_pclk))
>> -		return PTR_ERR(clk_pclk);
>> +	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);
>> +	}
>>   
>> -	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) {
>> +		snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
>> +			 "xtal_div");
>> +		hw = devm_clk_hw_register_divider_table(port->dev,
>> +							clk_name,
>> +							__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 {
>> +		snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
>> +			 "clk81_div4");
>> +		hw = devm_clk_hw_register_fixed_factor(port->dev,
>> +						       clk_name,
>> +						       __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;
>> +	}
> 
> The above is still wrong.
> 
> use_xtal_mux_parents initialize both parent to nothing
> And you init the parent in the conditional above.
> It is means only one path is actually set instead of both.
> 
> The mux always has 2 sources - Both should be set regardless of the HW version
> You just add
> * /4 on path 0 on legacy SoC
> * the funky divider on path 1 on newer SoC.
> 
You do have a point, so I was wondering if you had any suggestions.
>>   
>> -	port->uartclk = clk_get_rate(clk_baud);
>> +	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
>> +		 "use_xtal");
>> +	hw = __devm_clk_hw_register_mux(port->dev, NULL,
>> +					clk_name,
>> +					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);
>> +
>> +	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
>> +		 "baud_div");
>> +	hw = devm_clk_hw_register_divider(port->dev,
>> +					  clk_name,
>> +					  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 = hw->clk;
>>   
>>   	return 0;
>>   }
>>   
>>   static int meson_uart_probe(struct platform_device *pdev)
>>   {
>> +	struct meson_uart_data *private_data;
>>   	struct resource *res_mem;
>>   	struct uart_port *port;
>> +	struct clk *pclk;
>>   	u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */
>>   	int ret = 0;
>>   	int irq;
>> @@ -705,6 +764,15 @@ static int meson_uart_probe(struct platform_device *pdev)
>>   	if (!res_mem)
>>   		return -ENODEV;
>>   
>> +	pclk = devm_clk_get(&pdev->dev, "pclk");
>> +	if (IS_ERR(pclk))
>> +		return dev_err_probe(&pdev->dev, PTR_ERR(pclk),
>> +				     "Failed to get the 'pclk' clock\n");
>> +
>> +	ret = clk_prepare_enable(pclk);
>> +	if (ret)
>> +		return ret;
>> +
> 
> I think this is unbalanced.
I don't understand what you mean. How should I change it? Can you tell 
me more specifically.
> 
>>   	irq = platform_get_irq(pdev, 0);
>>   	if (irq < 0)
>>   		return irq;
>> @@ -724,9 +792,13 @@ static int meson_uart_probe(struct platform_device *pdev)
>>   	if (IS_ERR(port->membase))
>>   		return PTR_ERR(port->membase);
>>   
>> -	ret = meson_uart_probe_clocks(pdev, port);
>> -	if (ret)
>> -		return ret;
>> +	private_data = devm_kzalloc(&pdev->dev, sizeof(*private_data),
>> +				    GFP_KERNEL);
>> +	if (!private_data)
>> +		return -ENOMEM;
>> +
>> +	if (device_get_match_data(&pdev->dev))
>> +		private_data->use_xtal_clk = true;
>>   
>>   	port->iotype = UPIO_MEM;
>>   	port->mapbase = res_mem->start;
>> @@ -740,6 +812,11 @@ static int meson_uart_probe(struct platform_device *pdev)
>>   	port->x_char = 0;
>>   	port->ops = &meson_uart_ops;
>>   	port->fifosize = fifosize;
>> +	port->private_data = private_data;
>> +
>> +	ret = meson_uart_probe_clocks(port);
>> +	if (ret)
>> +		return ret;
>>   
>>   	meson_ports[pdev->id] = port;
>>   	platform_set_drvdata(pdev, port);
>> @@ -766,10 +843,22 @@ static int meson_uart_remove(struct platform_device *pdev)
>>   }
>>   
>>   static const struct of_device_id meson_uart_dt_match[] = {
>> -	{ .compatible = "amlogic,meson6-uart" },
>> -	{ .compatible = "amlogic,meson8-uart" },
>> -	{ .compatible = "amlogic,meson8b-uart" },
>> -	{ .compatible = "amlogic,meson-gx-uart" },
>> +	{
>> +		.compatible = "amlogic,meson6-uart",
>> +		.data = (void *)false,
>> +	},
>> +	{
>> +		.compatible = "amlogic,meson8-uart",
>> +		.data = (void *)false,
>> +	},
>> +	{
>> +		.compatible = "amlogic,meson8b-uart",
>> +		.data = (void *)false,
>> +	},
>> +	{
>> +		.compatible = "amlogic,meson-gx-uart",
>> +		.data = (void *)true,
>> +	},
>>   	{ /* sentinel */ },
>>   };
>>   MODULE_DEVICE_TABLE(of, meson_uart_dt_match);
>
diff mbox series

Patch

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 7570958d010c..92fa91c825e6 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 +75,11 @@ 
 #define AML_UART_POLL_USEC		5
 #define AML_UART_TIMEOUT_USEC		10000
 
+struct meson_uart_data {
+	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];
@@ -293,19 +297,17 @@  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 +397,20 @@  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);
 }
 
 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->baud_clk);
+	if (ret)
+		return ret;
+
 	return 0;
 }
 
@@ -629,57 +640,105 @@  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)
-{
-	struct clk *clk = NULL;
-	int ret;
-
-	clk = devm_clk_get(dev, id);
-	if (IS_ERR(clk))
-		return clk;
-
-	ret = clk_prepare_enable(clk);
-	if (ret) {
-		dev_err(dev, "couldn't enable clk\n");
-		return ERR_PTR(ret);
-	}
-
-	devm_add_action_or_reset(dev,
-			(void(*)(void *))clk_disable_unprepare,
-			clk);
-
-	return clk;
-}
+static struct clk_div_table xtal_div_table[] = {
+	{0, 3},
+	{1, 1},
+	{2, 2},
+	{3, 2},
+};
 
-static int meson_uart_probe_clocks(struct platform_device *pdev,
-				   struct uart_port *port)
+static int meson_uart_probe_clocks(struct uart_port *port)
 {
-	struct clk *clk_xtal = NULL;
-	struct clk *clk_pclk = NULL;
-	struct clk *clk_baud = NULL;
+	struct meson_uart_data *private_data = port->private_data;
+	struct clk *clk_baud, *clk_xtal;
+	struct clk_hw *hw;
+	char clk_name[32];
+	struct clk_parent_data use_xtal_mux_parents[2] = {
+		{ .index = -1, },
+		{ .index = -1, },
+	};
 
-	clk_pclk = meson_uart_probe_clock(&pdev->dev, "pclk");
-	if (IS_ERR(clk_pclk))
-		return PTR_ERR(clk_pclk);
+	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);
+	}
 
-	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) {
+		snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
+			 "xtal_div");
+		hw = devm_clk_hw_register_divider_table(port->dev,
+							clk_name,
+							__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 {
+		snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
+			 "clk81_div4");
+		hw = devm_clk_hw_register_fixed_factor(port->dev,
+						       clk_name,
+						       __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);
+	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
+		 "use_xtal");
+	hw = __devm_clk_hw_register_mux(port->dev, NULL,
+					clk_name,
+					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);
+
+	snprintf(clk_name, sizeof(clk_name), "%s#%s", dev_name(port->dev),
+		 "baud_div");
+	hw = devm_clk_hw_register_divider(port->dev,
+					  clk_name,
+					  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 = hw->clk;
 
 	return 0;
 }
 
 static int meson_uart_probe(struct platform_device *pdev)
 {
+	struct meson_uart_data *private_data;
 	struct resource *res_mem;
 	struct uart_port *port;
+	struct clk *pclk;
 	u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */
 	int ret = 0;
 	int irq;
@@ -705,6 +764,15 @@  static int meson_uart_probe(struct platform_device *pdev)
 	if (!res_mem)
 		return -ENODEV;
 
+	pclk = devm_clk_get(&pdev->dev, "pclk");
+	if (IS_ERR(pclk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(pclk),
+				     "Failed to get the 'pclk' clock\n");
+
+	ret = clk_prepare_enable(pclk);
+	if (ret)
+		return ret;
+
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0)
 		return irq;
@@ -724,9 +792,13 @@  static int meson_uart_probe(struct platform_device *pdev)
 	if (IS_ERR(port->membase))
 		return PTR_ERR(port->membase);
 
-	ret = meson_uart_probe_clocks(pdev, port);
-	if (ret)
-		return ret;
+	private_data = devm_kzalloc(&pdev->dev, sizeof(*private_data),
+				    GFP_KERNEL);
+	if (!private_data)
+		return -ENOMEM;
+
+	if (device_get_match_data(&pdev->dev))
+		private_data->use_xtal_clk = true;
 
 	port->iotype = UPIO_MEM;
 	port->mapbase = res_mem->start;
@@ -740,6 +812,11 @@  static int meson_uart_probe(struct platform_device *pdev)
 	port->x_char = 0;
 	port->ops = &meson_uart_ops;
 	port->fifosize = fifosize;
+	port->private_data = private_data;
+
+	ret = meson_uart_probe_clocks(port);
+	if (ret)
+		return ret;
 
 	meson_ports[pdev->id] = port;
 	platform_set_drvdata(pdev, port);
@@ -766,10 +843,22 @@  static int meson_uart_remove(struct platform_device *pdev)
 }
 
 static const struct of_device_id meson_uart_dt_match[] = {
-	{ .compatible = "amlogic,meson6-uart" },
-	{ .compatible = "amlogic,meson8-uart" },
-	{ .compatible = "amlogic,meson8b-uart" },
-	{ .compatible = "amlogic,meson-gx-uart" },
+	{
+		.compatible = "amlogic,meson6-uart",
+		.data = (void *)false,
+	},
+	{
+		.compatible = "amlogic,meson8-uart",
+		.data = (void *)false,
+	},
+	{
+		.compatible = "amlogic,meson8b-uart",
+		.data = (void *)false,
+	},
+	{
+		.compatible = "amlogic,meson-gx-uart",
+		.data = (void *)true,
+	},
 	{ /* sentinel */ },
 };
 MODULE_DEVICE_TABLE(of, meson_uart_dt_match);