[PATCH v3 1/2] usb: musb: dsps: implement vbus_status and set_vbus platform ops

[PATCH v3 1/2] usb: musb: dsps: implement vbus_status and set_vbus platform ops

[Lucas Martins Alves]

From: Lucas Martins Alves <lucas.alves@lumal21.com.br>

The DSPS glue layer (used on TI AM335x SoCs) was missing implementations
for the vbus_status and set_vbus platform ops defined in struct
musb_platform_ops.

Add dsps_musb_vbus_status() to report VBUS presence by reading the VBUS
field of MUSB_DEVCTL, and dsps_musb_set_vbus() to drive the SESSION bit
on MUSB_DEVCTL, enabling or disabling the USB session.

Register both callbacks in dsps_ops to allow the MUSB core to control
VBUS on AM335x-based platforms. This enables the USB core to perform a
VBUS power cycle as a recovery mechanism when a USB error condition is
detected, and also allows userspace to control VBUS state via the
standard USB sysfs interface.

Signed-off-by: Lucas Martins Alves <lucas.alves@lumal21.com.br>
---
v1 -> v2:
- remove musb_root_disconnect() from set_vbus path
- adjust context->devctl copy/update handling

v2 -> v3:
- fix patch description text
- fix devctl usage in set_vbus path
---
 drivers/usb/musb/musb_dsps.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c
index e3935f18dd56..e3dc2b6dc9b0 100644
--- a/drivers/usb/musb/musb_dsps.c
+++ b/drivers/usb/musb/musb_dsps.c
@@ -618,6 +618,34 @@ static int dsps_musb_recover(struct musb *musb)
 	return session_restart ? 0 : -EPIPE;
 }
 
+static int dsps_musb_vbus_status(struct musb *musb)
+{
+	u8 devctl = musb_readb(musb->mregs, MUSB_DEVCTL);
+
+	return (devctl & MUSB_DEVCTL_VBUS) == MUSB_DEVCTL_VBUS;
+}
+
+static void dsps_musb_set_vbus(struct musb *musb, int is_on)
+{
+	u8 devctl;
+
+	devctl = musb_readb(musb->mregs, MUSB_DEVCTL);
+
+	if (is_on) {
+		devctl |= MUSB_DEVCTL_SESSION;
+	} else {
+		/* Since we drop the session to turn off vbus, the connection cannot survive */
+		if( musb->port1_status & USB_PORT_STAT_CONNECTION )
+			musb->port1_status |= (USB_PORT_STAT_C_CONNECTION << 16);
+		musb->port1_status &= ~( USB_PORT_STAT_CONNECTION |
+			                     USB_PORT_STAT_HIGH_SPEED |
+								 USB_PORT_STAT_LOW_SPEED );
+		devctl &= ~MUSB_DEVCTL_SESSION;
+	}
+
+	musb_writeb(musb->mregs, MUSB_DEVCTL, devctl);
+}
+
 /* Similar to am35x, dm81xx support only 32-bit read operation */
 static void dsps_read_fifo32(struct musb_hw_ep *hw_ep, u16 len, u8 *dst)
 {
@@ -702,6 +730,8 @@ static struct musb_platform_ops dsps_ops = {
 
 	.set_mode	= dsps_musb_set_mode,
 	.recover	= dsps_musb_recover,
+	.vbus_status	= dsps_musb_vbus_status,
+	.set_vbus	= dsps_musb_set_vbus,
 	.clear_ep_rxintr = dsps_musb_clear_ep_rxintr,
 };
 
-- 
2.53.0

[PATCH v3 2/2] usb: musb: gadget: fix MUSB_DEVCTL race condition in set_vbus

[Lucas Martins Alves]

From: Lucas Martins Alves <lucas.alves@lumal21.com.br>

During gadget initialization, musb_gadget_start() releases musb->lock,
enables interrupts via musb_start(), and then invokes
musb_platform_set_vbus(musb, 1) in a lockless context.

If musb_interrupt() fires concurrently, it will take musb->lock and
modify MUSB_DEVCTL. Those changes could be silently overwritten when
the callback writes back the stale cached devctl value, causing state
corruption due to the unlocked read-modify-write race condition.

Fix this by acquiring musb->lock before calling musb_platform_set_vbus()
in musb_gadget_start(). This ensures the register operation is atomic
with respect to concurrent interrupt handlers, preventing the RMW race
condition while avoiding deadlock scenarios where this function is called
from interrupt context (which already holds the lock).

Signed-off-by: Lucas Martins Alves <lucas.alves@lumal21.com.br>
---
v2 -> v3
- No changes
---
 drivers/usb/musb/musb_gadget.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index 016d3f3fc1e0..8eca252423e9 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -1857,8 +1857,11 @@ static int musb_gadget_start(struct usb_gadget *g,
 	 * handles power budgeting ... this way also
 	 * ensures HdrcStart is indirectly called.
 	 */
-	if (musb->xceiv && musb->xceiv->last_event == USB_EVENT_ID)
+	if (musb->xceiv && musb->xceiv->last_event == USB_EVENT_ID) {
+		spin_lock_irqsave(&musb->lock, flags);
 		musb_platform_set_vbus(musb, 1);
+		spin_unlock_irqrestore(&musb->lock, flags);
+	}
 
 	pm_runtime_put_autosuspend(musb->controller);
 
-- 
2.53.0

[PATCH v4] usb: musb: dsps: implement vbus_status and set_vbus platform ops

[Lucas Martins Alves]

From: Lucas Martins Alves <lucas.alves@lumal21.com.br>

The DSPS glue layer (used on TI AM335x SoCs) was missing implementations
for the vbus_status and set_vbus platform ops defined in struct
musb_platform_ops.

Add dsps_musb_vbus_status() to report VBUS presence by reading the VBUS
field of MUSB_DEVCTL, and dsps_musb_set_vbus() to drive the SESSION bit
on MUSB_DEVCTL, enabling or disabling the USB session.

Register both callbacks in dsps_ops to allow the MUSB core to control
VBUS on AM335x-based platforms. This enables the USB core to perform a
VBUS power cycle as a recovery mechanism when a USB error condition is
detected, and also allows userspace to control VBUS state via the
standard USB sysfs interface.

Signed-off-by: Lucas Martins Alves <lucas.alves@lumal21.com.br>
---
v1 -> v2:
- remove musb_root_disconnect() from set_vbus path
- adjust context->devctl copy/update handling

v2 -> v3:
- fix patch description text
- fix devctl usage in set_vbus path
---
 drivers/usb/musb/musb_dsps.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c
index e3935f18dd56..aecb5c074c53 100644
--- a/drivers/usb/musb/musb_dsps.c
+++ b/drivers/usb/musb/musb_dsps.c
@@ -618,6 +618,36 @@ static int dsps_musb_recover(struct musb *musb)
 	return session_restart ? 0 : -EPIPE;
 }
 
+static int dsps_musb_vbus_status(struct musb *musb)
+{
+	u8 devctl = musb_readb(musb->mregs, MUSB_DEVCTL);
+
+	return (devctl & MUSB_DEVCTL_VBUS) == MUSB_DEVCTL_VBUS;
+}
+
+static void dsps_musb_set_vbus(struct musb *musb, int is_on)
+{
+	u8 devctl;
+
+	devctl = musb_readb(musb->mregs, MUSB_DEVCTL);
+
+	if (is_on) {
+		devctl |= MUSB_DEVCTL_SESSION;
+	} else {
+		/* Since we drop the session to turn off vbus, the connection cannot survive */
+		if( musb->port1_status & USB_PORT_STAT_CONNECTION )
+			musb->port1_status |= (USB_PORT_STAT_C_CONNECTION << 16);
+		musb->port1_status &= ~( USB_PORT_STAT_CONNECTION |
+			                     USB_PORT_STAT_HIGH_SPEED |
+								 USB_PORT_STAT_LOW_SPEED );
+		devctl &= ~MUSB_DEVCTL_SESSION;
+		usb_hcd_poll_rh_status(musb->hcd);
+		musb->is_active = 0;
+	}
+
+	musb_writeb(musb->mregs, MUSB_DEVCTL, devctl);
+}
+
 /* Similar to am35x, dm81xx support only 32-bit read operation */
 static void dsps_read_fifo32(struct musb_hw_ep *hw_ep, u16 len, u8 *dst)
 {
@@ -702,6 +732,8 @@ static struct musb_platform_ops dsps_ops = {
 
 	.set_mode	= dsps_musb_set_mode,
 	.recover	= dsps_musb_recover,
+	.vbus_status	= dsps_musb_vbus_status,
+	.set_vbus	= dsps_musb_set_vbus,
 	.clear_ep_rxintr = dsps_musb_clear_ep_rxintr,
 };
 
-- 
2.53.0

Re: [PATCH v4] usb: musb: dsps: implement vbus_status and set_vbus platform ops

[gregkh]

On Thu, Jul 16, 2026 at 05:05:54PM +0000, Lucas Martins Alves wrote:
> From: Lucas Martins Alves <lucas.alves@lumal21.com.br>
> 
> The DSPS glue layer (used on TI AM335x SoCs) was missing implementations
> for the vbus_status and set_vbus platform ops defined in struct
> musb_platform_ops.
> 
> Add dsps_musb_vbus_status() to report VBUS presence by reading the VBUS
> field of MUSB_DEVCTL, and dsps_musb_set_vbus() to drive the SESSION bit
> on MUSB_DEVCTL, enabling or disabling the USB session.
> 
> Register both callbacks in dsps_ops to allow the MUSB core to control
> VBUS on AM335x-based platforms. This enables the USB core to perform a
> VBUS power cycle as a recovery mechanism when a USB error condition is
> detected, and also allows userspace to control VBUS state via the
> standard USB sysfs interface.
> 
> Signed-off-by: Lucas Martins Alves <lucas.alves@lumal21.com.br>
> ---
> v1 -> v2:
> - remove musb_root_disconnect() from set_vbus path
> - adjust context->devctl copy/update handling
> 
> v2 -> v3:
> - fix patch description text
> - fix devctl usage in set_vbus path
> ---
>  drivers/usb/musb/musb_dsps.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)

I'm confused, what about patch 2?

THis series is all intermixed, can you start a new thread, and send just
what you want reviewed/accepted here?  I'm lost...

thanks,

gre k-h

RE: [PATCH v4] usb: musb: dsps: implement vbus_status and set_vbus platform ops

[Lucas Martins Alves]

Hi,
I would like to apologize for the confusion regarding the previous patch submissions.
I generate and manage patches from an environment with restricted email access. As a result, I am unable to use the traditional patch submission tools and workflows, which unfortunately led to several mistakes while sending this patch series.
To avoid further confusion, I have recreated and resubmitted the patches as:
[PATCH v5] usb: musb: dsps: implement vbus_status and set_vbus platform ops
This version correctly reflects the changes that I intended to submit for review. Please disregard the earlier submissions and use the v5 patch as the basis for any review comments.
I apologize for the noise caused by the previous iterations and appreciate your patience and feedback.
Thank you for your time and review.
Best regards,

Lucas Martins Alves


________________________________________
De: gregkh@linuxfoundation.org <gregkh@linuxfoundation.org>
Enviado: sexta-feira, 17 de julho de 2026 06:41
Para: Lucas Martins Alves <lucas.alves@lumal21.com.br>
Cc: b-liu@ti.com <b-liu@ti.com>; linux-usb@vger.kernel.org <linux-usb@vger.kernel.org>; linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>
Assunto: Re: [PATCH v4] usb: musb: dsps: implement vbus_status and set_vbus platform ops
 
On Thu, Jul 16, 2026 at 05:05:54PM +0000, Lucas Martins Alves wrote:
> From: Lucas Martins Alves <lucas.alves@lumal21.com.br>
>
> The DSPS glue layer (used on TI AM335x SoCs) was missing implementations
> for the vbus_status and set_vbus platform ops defined in struct
> musb_platform_ops.
>
> Add dsps_musb_vbus_status() to report VBUS presence by reading the VBUS
> field of MUSB_DEVCTL, and dsps_musb_set_vbus() to drive the SESSION bit
> on MUSB_DEVCTL, enabling or disabling the USB session.
>
> Register both callbacks in dsps_ops to allow the MUSB core to control
> VBUS on AM335x-based platforms. This enables the USB core to perform a
> VBUS power cycle as a recovery mechanism when a USB error condition is
> detected, and also allows userspace to control VBUS state via the
> standard USB sysfs interface.
>
> Signed-off-by: Lucas Martins Alves <lucas.alves@lumal21.com.br>
> ---
> v1 -> v2:
> - remove musb_root_disconnect() from set_vbus path
> - adjust context->devctl copy/update handling
>
> v2 -> v3:
> - fix patch description text
> - fix devctl usage in set_vbus path
> ---
>  drivers/usb/musb/musb_dsps.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)

I'm confused, what about patch 2?

THis series is all intermixed, can you start a new thread, and send just
what you want reviewed/accepted here?  I'm lost...

thanks,

gre k-h