[PATCH] serial: sprd: Return -EPROBE_DEFER when uart clock is not ready

[PATCH] serial: sprd: Return -EPROBE_DEFER when uart clock is not ready

[Wenhua Lin]

In sprd_clk_init(), when devm_clk_get() returns -EPROBE_DEFER
for either uart or source clock, we should propagate the
error instead of just warning and continuing with NULL clocks.

Currently the driver only emits a warning when clock acquisition
fails and proceeds with NULL clock pointers. This can lead to
issues later when the clocks are actually needed. More importantly,
when the clock provider is not ready yet and returns -EPROBE_DEFER,
we should return this error to allow deferred probing.

This change adds explicit checks for -EPROBE_DEFER after both:
1. devm_clk_get(uport->dev, uart)
2. devm_clk_get(uport->dev, source)

When -EPROBE_DEFER is encountered, the function now returns
-EPROBE_DEFER to let the driver framework retry probing
later when the clock dependencies are resolved.

Signed-off-by: Wenhua Lin <Wenhua.Lin@unisoc.com>
---
 drivers/tty/serial/sprd_serial.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
index 8c9366321f8e..092755f35683 100644
--- a/drivers/tty/serial/sprd_serial.c
+++ b/drivers/tty/serial/sprd_serial.c
@@ -1133,6 +1133,9 @@ static int sprd_clk_init(struct uart_port *uport)
 
 	clk_uart = devm_clk_get(uport->dev, "uart");
 	if (IS_ERR(clk_uart)) {
+		if (PTR_ERR(clk_uart) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+
 		dev_warn(uport->dev, "uart%d can't get uart clock\n",
 			 uport->line);
 		clk_uart = NULL;
@@ -1140,6 +1143,9 @@ static int sprd_clk_init(struct uart_port *uport)
 
 	clk_parent = devm_clk_get(uport->dev, "source");
 	if (IS_ERR(clk_parent)) {
+		if (PTR_ERR(clk_parent) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+
 		dev_warn(uport->dev, "uart%d can't get source clock\n",
 			 uport->line);
 		clk_parent = NULL;
-- 
2.34.1

Re: [PATCH] serial: sprd: Return -EPROBE_DEFER when uart clock is not ready

[Chunyan Zhang]

On Wed, 22 Oct 2025 at 11:09, Wenhua Lin <Wenhua.Lin@unisoc.com> wrote:
>
> In sprd_clk_init(), when devm_clk_get() returns -EPROBE_DEFER
> for either uart or source clock, we should propagate the
> error instead of just warning and continuing with NULL clocks.
>
> Currently the driver only emits a warning when clock acquisition
> fails and proceeds with NULL clock pointers. This can lead to
> issues later when the clocks are actually needed. More importantly,
> when the clock provider is not ready yet and returns -EPROBE_DEFER,
> we should return this error to allow deferred probing.
>
> This change adds explicit checks for -EPROBE_DEFER after both:
> 1. devm_clk_get(uport->dev, uart)
> 2. devm_clk_get(uport->dev, source)
>
> When -EPROBE_DEFER is encountered, the function now returns
> -EPROBE_DEFER to let the driver framework retry probing
> later when the clock dependencies are resolved.
>
> Signed-off-by: Wenhua Lin <Wenhua.Lin@unisoc.com>
> ---
>  drivers/tty/serial/sprd_serial.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> index 8c9366321f8e..092755f35683 100644
> --- a/drivers/tty/serial/sprd_serial.c
> +++ b/drivers/tty/serial/sprd_serial.c
> @@ -1133,6 +1133,9 @@ static int sprd_clk_init(struct uart_port *uport)
>
>         clk_uart = devm_clk_get(uport->dev, "uart");
>         if (IS_ERR(clk_uart)) {
> +               if (PTR_ERR(clk_uart) == -EPROBE_DEFER)
> +                       return -EPROBE_DEFER;
> +

You are making this clock mandatory, sprd_serial driver could work as
serial ports for logs output without this "uart" clock.

>                 dev_warn(uport->dev, "uart%d can't get uart clock\n",
>                          uport->line);
>                 clk_uart = NULL;
> @@ -1140,6 +1143,9 @@ static int sprd_clk_init(struct uart_port *uport)
>
>         clk_parent = devm_clk_get(uport->dev, "source");
>         if (IS_ERR(clk_parent)) {
> +               if (PTR_ERR(clk_parent) == -EPROBE_DEFER)
> +                       return -EPROBE_DEFER;
> +
>                 dev_warn(uport->dev, "uart%d can't get source clock\n",
>                          uport->line);
>                 clk_parent = NULL;
> --
> 2.34.1
>

Re: [PATCH] serial: sprd: Return -EPROBE_DEFER when uart clock is not ready

[wenhua lin]

On Wed, Oct 22, 2025 at 2:55 PM Chunyan Zhang <zhang.lyra@gmail.com> wrote:
>
> On Wed, 22 Oct 2025 at 11:09, Wenhua Lin <Wenhua.Lin@unisoc.com> wrote:
> >
> > In sprd_clk_init(), when devm_clk_get() returns -EPROBE_DEFER
> > for either uart or source clock, we should propagate the
> > error instead of just warning and continuing with NULL clocks.
> >
> > Currently the driver only emits a warning when clock acquisition
> > fails and proceeds with NULL clock pointers. This can lead to
> > issues later when the clocks are actually needed. More importantly,
> > when the clock provider is not ready yet and returns -EPROBE_DEFER,
> > we should return this error to allow deferred probing.
> >
> > This change adds explicit checks for -EPROBE_DEFER after both:
> > 1. devm_clk_get(uport->dev, uart)
> > 2. devm_clk_get(uport->dev, source)
> >
> > When -EPROBE_DEFER is encountered, the function now returns
> > -EPROBE_DEFER to let the driver framework retry probing
> > later when the clock dependencies are resolved.
> >
> > Signed-off-by: Wenhua Lin <Wenhua.Lin@unisoc.com>
> > ---
> >  drivers/tty/serial/sprd_serial.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> > index 8c9366321f8e..092755f35683 100644
> > --- a/drivers/tty/serial/sprd_serial.c
> > +++ b/drivers/tty/serial/sprd_serial.c
> > @@ -1133,6 +1133,9 @@ static int sprd_clk_init(struct uart_port *uport)
> >
> >         clk_uart = devm_clk_get(uport->dev, "uart");
> >         if (IS_ERR(clk_uart)) {
> > +               if (PTR_ERR(clk_uart) == -EPROBE_DEFER)
> > +                       return -EPROBE_DEFER;
> > +
>
> You are making this clock mandatory, sprd_serial driver could work as
> serial ports for logs output without this "uart" clock.

Hi chunyan:
   Thank you very much for your review.
   This clock is actually mandatory now，some SPRD project use default 26M clock,
   some new SPRD project use default 24M clock.  If driver can't parse
this clock correctly,
   driver will configure wrong baudrate and make the log garbled.

Thanks

>
> >                 dev_warn(uport->dev, "uart%d can't get uart clock\n",
> >                          uport->line);
> >                 clk_uart = NULL;
> > @@ -1140,6 +1143,9 @@ static int sprd_clk_init(struct uart_port *uport)
> >
> >         clk_parent = devm_clk_get(uport->dev, "source");
> >         if (IS_ERR(clk_parent)) {
> > +               if (PTR_ERR(clk_parent) == -EPROBE_DEFER)
> > +                       return -EPROBE_DEFER;
> > +
> >                 dev_warn(uport->dev, "uart%d can't get source clock\n",
> >                          uport->line);
> >                 clk_parent = NULL;
> > --
> > 2.34.1
> >

Re: [PATCH] serial: sprd: Return -EPROBE_DEFER when uart clock is not ready

[Chunyan Zhang]

Hi Wenhua,

On Thu, 23 Oct 2025 at 10:10, wenhua lin <wenhua.lin1994@gmail.com> wrote:
>
> On Wed, Oct 22, 2025 at 2:55 PM Chunyan Zhang <zhang.lyra@gmail.com> wrote:
> >
> > On Wed, 22 Oct 2025 at 11:09, Wenhua Lin <Wenhua.Lin@unisoc.com> wrote:
> > >
> > > In sprd_clk_init(), when devm_clk_get() returns -EPROBE_DEFER
> > > for either uart or source clock, we should propagate the
> > > error instead of just warning and continuing with NULL clocks.
> > >
> > > Currently the driver only emits a warning when clock acquisition
> > > fails and proceeds with NULL clock pointers. This can lead to
> > > issues later when the clocks are actually needed. More importantly,
> > > when the clock provider is not ready yet and returns -EPROBE_DEFER,
> > > we should return this error to allow deferred probing.
> > >
> > > This change adds explicit checks for -EPROBE_DEFER after both:
> > > 1. devm_clk_get(uport->dev, uart)
> > > 2. devm_clk_get(uport->dev, source)
> > >
> > > When -EPROBE_DEFER is encountered, the function now returns
> > > -EPROBE_DEFER to let the driver framework retry probing
> > > later when the clock dependencies are resolved.
> > >
> > > Signed-off-by: Wenhua Lin <Wenhua.Lin@unisoc.com>
> > > ---
> > >  drivers/tty/serial/sprd_serial.c | 6 ++++++
> > >  1 file changed, 6 insertions(+)
> > >
> > > diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> > > index 8c9366321f8e..092755f35683 100644
> > > --- a/drivers/tty/serial/sprd_serial.c
> > > +++ b/drivers/tty/serial/sprd_serial.c
> > > @@ -1133,6 +1133,9 @@ static int sprd_clk_init(struct uart_port *uport)
> > >
> > >         clk_uart = devm_clk_get(uport->dev, "uart");
> > >         if (IS_ERR(clk_uart)) {
> > > +               if (PTR_ERR(clk_uart) == -EPROBE_DEFER)
> > > +                       return -EPROBE_DEFER;
> > > +
> >
> > You are making this clock mandatory, sprd_serial driver could work as
> > serial ports for logs output without this "uart" clock.
>
> Hi chunyan:
>    Thank you very much for your review.
>    This clock is actually mandatory now，some SPRD project use default 26M clock,
>    some new SPRD project use default 24M clock.  If driver can't parse

Oh I see, then you can set a different default clock according to the
compatible string, that's saying make SPRD_DEFAULT_SOURCE_CLK to be an
element of "of_device_id.data".

Thanks,
Chunyan

> this clock correctly,
>    driver will configure wrong baudrate and make the log garbled.
>
> Thanks
>
> >
> > >                 dev_warn(uport->dev, "uart%d can't get uart clock\n",
> > >                          uport->line);
> > >                 clk_uart = NULL;
> > > @@ -1140,6 +1143,9 @@ static int sprd_clk_init(struct uart_port *uport)
> > >
> > >         clk_parent = devm_clk_get(uport->dev, "source");
> > >         if (IS_ERR(clk_parent)) {
> > > +               if (PTR_ERR(clk_parent) == -EPROBE_DEFER)
> > > +                       return -EPROBE_DEFER;
> > > +
> > >                 dev_warn(uport->dev, "uart%d can't get source clock\n",
> > >                          uport->line);
> > >                 clk_parent = NULL;
> > > --
> > > 2.34.1
> > >

Re: [PATCH] serial: sprd: Return -EPROBE_DEFER when uart clock is not ready

[wenhua lin]

On Fri, Oct 24, 2025 at 9:42 AM Chunyan Zhang <zhang.lyra@gmail.com> wrote:
>
> Hi Wenhua,
>
> On Thu, 23 Oct 2025 at 10:10, wenhua lin <wenhua.lin1994@gmail.com> wrote:
> >
> > On Wed, Oct 22, 2025 at 2:55 PM Chunyan Zhang <zhang.lyra@gmail.com> wrote:
> > >
> > > On Wed, 22 Oct 2025 at 11:09, Wenhua Lin <Wenhua.Lin@unisoc.com> wrote:
> > > >
> > > > In sprd_clk_init(), when devm_clk_get() returns -EPROBE_DEFER
> > > > for either uart or source clock, we should propagate the
> > > > error instead of just warning and continuing with NULL clocks.
> > > >
> > > > Currently the driver only emits a warning when clock acquisition
> > > > fails and proceeds with NULL clock pointers. This can lead to
> > > > issues later when the clocks are actually needed. More importantly,
> > > > when the clock provider is not ready yet and returns -EPROBE_DEFER,
> > > > we should return this error to allow deferred probing.
> > > >
> > > > This change adds explicit checks for -EPROBE_DEFER after both:
> > > > 1. devm_clk_get(uport->dev, uart)
> > > > 2. devm_clk_get(uport->dev, source)
> > > >
> > > > When -EPROBE_DEFER is encountered, the function now returns
> > > > -EPROBE_DEFER to let the driver framework retry probing
> > > > later when the clock dependencies are resolved.
> > > >
> > > > Signed-off-by: Wenhua Lin <Wenhua.Lin@unisoc.com>
> > > > ---
> > > >  drivers/tty/serial/sprd_serial.c | 6 ++++++
> > > >  1 file changed, 6 insertions(+)
> > > >
> > > > diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> > > > index 8c9366321f8e..092755f35683 100644
> > > > --- a/drivers/tty/serial/sprd_serial.c
> > > > +++ b/drivers/tty/serial/sprd_serial.c
> > > > @@ -1133,6 +1133,9 @@ static int sprd_clk_init(struct uart_port *uport)
> > > >
> > > >         clk_uart = devm_clk_get(uport->dev, "uart");
> > > >         if (IS_ERR(clk_uart)) {
> > > > +               if (PTR_ERR(clk_uart) == -EPROBE_DEFER)
> > > > +                       return -EPROBE_DEFER;
> > > > +
> > >
> > > You are making this clock mandatory, sprd_serial driver could work as
> > > serial ports for logs output without this "uart" clock.
> >
> > Hi chunyan:
> >    Thank you very much for your review.
> >    This clock is actually mandatory now，some SPRD project use default 26M clock,
> >    some new SPRD project use default 24M clock.  If driver can't parse
>
> Oh I see, then you can set a different default clock according to the
> compatible string, that's saying make SPRD_DEFAULT_SOURCE_CLK to be an
> element of "of_device_id.data".
>
> Thanks,
> Chunyan

Hi chunyan:
   This is not the current issue; it will be considered in future modifications.
   The main reason for this change is that the UART driver is
built-in, while the CLK driver is loaded as a module (ko).
   There may be a situation where the UART driver is loaded first.
   If an EPROBE_DEFER error occurs, the driver will return directly
and continue waiting for the CLK driver to complete loading.

Thanks
>
> > this clock correctly,
> >    driver will configure wrong baudrate and make the log garbled.
> >
> > Thanks
> >
> > >
> > > >                 dev_warn(uport->dev, "uart%d can't get uart clock\n",
> > > >                          uport->line);
> > > >                 clk_uart = NULL;
> > > > @@ -1140,6 +1143,9 @@ static int sprd_clk_init(struct uart_port *uport)
> > > >
> > > >         clk_parent = devm_clk_get(uport->dev, "source");
> > > >         if (IS_ERR(clk_parent)) {
> > > > +               if (PTR_ERR(clk_parent) == -EPROBE_DEFER)
> > > > +                       return -EPROBE_DEFER;
> > > > +
> > > >                 dev_warn(uport->dev, "uart%d can't get source clock\n",
> > > >                          uport->line);
> > > >                 clk_parent = NULL;
> > > > --
> > > > 2.34.1
> > > >