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serial: 8250_of: Add clock_notifier

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The UART's input clock rate can change at runtime but this is not
handled by the driver.

Add a clock_notifier callback that updates the divisors when the input
clock is updated. The serial8250_update_uartclk() is used to do so.
PRE_RATE_CHANGE and ABORT_RATE_CHANGE notifications are ignored, only
the POST_RATE_CHANGE is used. Not using PRE_RATE_CHANGE notification can
result in a few corrupted bytes during frequency transitions but, IMHO,
it can be acceptable in many use cases.

It has been tested on a DAVINCI/OMAP-L138 processor.

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
Reviewed-by: Herve Codina <herve.codina@bootlin.com>
Link: https://lore.kernel.org/r/20240405120552.35991-1-bastien.curutchet@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Bastien Curutchet 2024-04-05 14:05:52 +02:00 committed by Greg Kroah-Hartman
parent 8c278ade67
commit 32f6ec282f
1 changed files with 37 additions and 0 deletions
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37
drivers/tty/serial/8250/8250_of.c
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@ -18,6 +18,7 @@
#include <linux/pm_runtime.h> #include <linux/pm_runtime.h>
#include <linux/clk.h> #include <linux/clk.h>
#include <linux/reset.h> #include <linux/reset.h>
#include <linux/notifier.h>
#include "8250.h" #include "8250.h"
@ -26,6 +27,7 @@ struct of_serial_info {
struct reset_control *rst; struct reset_control *rst;
int type; int type;
int line; int line;
struct notifier_block clk_notifier;
}; };
/* Nuvoton NPCM timeout register */ /* Nuvoton NPCM timeout register */
@ -58,6 +60,26 @@ static int npcm_setup(struct uart_port *port)
return 0; return 0;
} }
static inline struct of_serial_info *clk_nb_to_info(struct notifier_block *nb)
{
return container_of(nb, struct of_serial_info, clk_notifier);
}
static int of_platform_serial_clk_notifier_cb(struct notifier_block *nb, unsigned long event,
void *data)
{
struct of_serial_info *info = clk_nb_to_info(nb);
struct uart_8250_port *port8250 = serial8250_get_port(info->line);
struct clk_notifier_data *ndata = data;
if (event == POST_RATE_CHANGE) {
serial8250_update_uartclk(&port8250->port, ndata->new_rate);
return NOTIFY_OK;
}
return NOTIFY_DONE;
}
/* /*
* Fill a struct uart_port for a given device node * Fill a struct uart_port for a given device node
*/ */
@ -218,7 +240,19 @@ static int of_platform_serial_probe(struct platform_device *ofdev)
info->type = port_type; info->type = port_type;
info->line = ret; info->line = ret;
platform_set_drvdata(ofdev, info); platform_set_drvdata(ofdev, info);
if (info->clk) {
info->clk_notifier.notifier_call = of_platform_serial_clk_notifier_cb;
ret = clk_notifier_register(info->clk, &info->clk_notifier);
if (ret) {
dev_err_probe(port8250.port.dev, ret, "Failed to set the clock notifier\n");
goto err_unregister;
}
}
return 0; return 0;
err_unregister:
serial8250_unregister_port(info->line);
err_dispose: err_dispose:
pm_runtime_put_sync(&ofdev->dev); pm_runtime_put_sync(&ofdev->dev);
pm_runtime_disable(&ofdev->dev); pm_runtime_disable(&ofdev->dev);
@ -234,6 +268,9 @@ static void of_platform_serial_remove(struct platform_device *ofdev)
{ {
struct of_serial_info *info = platform_get_drvdata(ofdev); struct of_serial_info *info = platform_get_drvdata(ofdev);
if (info->clk)
clk_notifier_unregister(info->clk, &info->clk_notifier);
serial8250_unregister_port(info->line); serial8250_unregister_port(info->line);
reset_control_assert(info->rst); reset_control_assert(info->rst);