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serial: 8250_dw: remove clock-notifier infrastructure

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The clock notifier and matching work_struct in dw8250_data were added
in 2020 for the Baikal-T1 SoC, whose multiple UART ports share a
single reference clock and need to be informed when another consumer
re-rates that clock.

Baikal SoC support has since been removed from the kernel (see e.g.
commit 5d6c477687 ("clk: baikal-t1: Remove not-going-to-be-supported
code for Baikal SoC") and the matching removals across bus/, mtd/,
PCI/, hwmon/, memory/). No remaining in-tree user needs the
cross-device baudclk rate-change notification path: the only
configuration that wired up the notifier was Baikal-T1's shared
reference clock topology.

Drop the now-unused clock-notifier and its deferred-update worker:

  - struct dw8250_data fields clk_notifier and clk_work,
  - the clk_to_dw8250_data() and work_to_dw8250_data() helpers,
  - the dw8250_clk_work_cb() and dw8250_clk_notifier_cb() callbacks,
  - the INIT_WORK / notifier_call setup in dw8250_probe(),
  - the clk_notifier_register() / queue_work() in dw8250_probe(),
  - the matching clk_notifier_unregister() / flush_work() in
    dw8250_remove(),
  - the stale comment in dw8250_set_termios() about the worker
    blocking,
  - the linux/notifier.h and linux/workqueue.h includes that are
    no longer used.

dw8250_set_termios() keeps calling clk_set_rate() directly, which is
all the remaining single-UART configurations require.

Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20260514143746.23671-3-sozdayvek@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Stepan Ionichev 2026-05-14 19:37:46 +05:00 committed by Greg Kroah-Hartman
parent 10fc708b4d
commit 01569a29af
1 changed files with 0 additions and 81 deletions
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81
drivers/tty/serial/8250/8250_dw.c
View File

@ -19,13 +19,11 @@
#include <linux/lockdep.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/property.h>
#include <linux/reset.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <asm/byteorder.h>
@ -75,8 +73,6 @@ struct dw8250_data {
u32 msr_mask_off;
struct clk *clk;
struct clk *pclk;
struct notifier_block clk_notifier;
struct work_struct clk_work;
struct reset_control *rst;
unsigned int skip_autocfg:1;
@ -91,16 +87,6 @@ static inline struct dw8250_data *to_dw8250_data(struct dw8250_port_data *data)
return container_of(data, struct dw8250_data, data);
}
static inline struct dw8250_data *clk_to_dw8250_data(struct notifier_block *nb)
{
return container_of(nb, struct dw8250_data, clk_notifier);
}
static inline struct dw8250_data *work_to_dw8250_data(struct work_struct *work)
{
return container_of(work, struct dw8250_data, clk_work);
}
static inline u32 dw8250_modify_msr(struct uart_port *p, unsigned int offset, u32 value)
{
struct dw8250_data *d = to_dw8250_data(p->private_data);
@ -473,46 +459,6 @@ static int dw8250_handle_irq(struct uart_port *p)
return 1;
}
static void dw8250_clk_work_cb(struct work_struct *work)
{
struct dw8250_data *d = work_to_dw8250_data(work);
struct uart_8250_port *up;
unsigned long rate;
rate = clk_get_rate(d->clk);
if (rate <= 0)
return;
up = serial8250_get_port(d->data.line);
serial8250_update_uartclk(&up->port, rate);
}
static int dw8250_clk_notifier_cb(struct notifier_block *nb,
unsigned long event, void *data)
{
struct dw8250_data *d = clk_to_dw8250_data(nb);
/*
* We have no choice but to defer the uartclk update due to two
* deadlocks. First one is caused by a recursive mutex lock which
* happens when clk_set_rate() is called from dw8250_set_termios().
* Second deadlock is more tricky and is caused by an inverted order of
* the clk and tty-port mutexes lock. It happens if clock rate change
* is requested asynchronously while set_termios() is executed between
* tty-port mutex lock and clk_set_rate() function invocation and
* vise-versa. Anyway if we didn't have the reference clock alteration
* in the dw8250_set_termios() method we wouldn't have needed this
* deferred event handling complication.
*/
if (event == POST_RATE_CHANGE) {
queue_work(system_dfl_wq, &d->clk_work);
return NOTIFY_OK;
}
return NOTIFY_DONE;
}
static void
dw8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
{
@ -536,10 +482,6 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
clk_disable_unprepare(d->clk);
rate = clk_round_rate(d->clk, newrate);
if (rate > 0) {
/*
* Note that any clock-notifier worker will block in
* serial8250_update_uartclk() until we are done.
*/
ret = clk_set_rate(d->clk, newrate);
if (!ret)
p->uartclk = rate;
@ -772,9 +714,6 @@ static int dw8250_probe(struct platform_device *pdev)
return dev_err_probe(dev, PTR_ERR(data->clk),
"failed to get baudclk\n");
INIT_WORK(&data->clk_work, dw8250_clk_work_cb);
data->clk_notifier.notifier_call = dw8250_clk_notifier_cb;
if (data->clk)
p->uartclk = clk_get_rate(data->clk);
@ -832,20 +771,6 @@ static int dw8250_probe(struct platform_device *pdev)
if (data->data.line < 0)
return data->data.line;
/*
* Some platforms may provide a reference clock shared between several
* devices. In this case any clock state change must be known to the
* UART port at least post factum.
*/
if (data->clk) {
err = clk_notifier_register(data->clk, &data->clk_notifier);
if (err) {
serial8250_unregister_port(data->data.line);
return dev_err_probe(dev, err, "Failed to set the clock notifier\n");
}
queue_work(system_dfl_wq, &data->clk_work);
}
platform_set_drvdata(pdev, data);
pm_runtime_enable(dev);
@ -860,12 +785,6 @@ static void dw8250_remove(struct platform_device *pdev)
pm_runtime_get_sync(dev);
if (data->clk) {
clk_notifier_unregister(data->clk, &data->clk_notifier);
flush_work(&data->clk_work);
}
serial8250_unregister_port(data->data.line);
pm_runtime_disable(dev);