Re: [PATCH v2] usb: cdns3: gadget: Fix g_audio use case when connected to Super-Speed host

From: Roger Quadros
Date: Thu Oct 31 2019 - 06:35:41 EST


Hi,

On 31/10/2019 10:55, Felipe Balbi wrote:

Hi,

Roger Quadros <rogerq@xxxxxx> writes:

Take into account gadget driver's speed limit when programming
controller speed.

Fixes: commit 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Signed-off-by: Roger Quadros <rogerq@xxxxxx>
Acked-by: Peter Chen <peter.chen@xxxxxxx>
---

Changelog:
v2
- Add Fixes line

drivers/usb/cdns3/gadget.c | 31 ++++++++++++++++++++++++++-----
1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
index 40dad4e8d0dc..1c724c20d468 100644
--- a/drivers/usb/cdns3/gadget.c
+++ b/drivers/usb/cdns3/gadget.c
@@ -2338,9 +2338,35 @@ static int cdns3_gadget_udc_start(struct usb_gadget *gadget,
{
struct cdns3_device *priv_dev = gadget_to_cdns3_device(gadget);
unsigned long flags;
+ enum usb_device_speed max_speed = driver->max_speed;
spin_lock_irqsave(&priv_dev->lock, flags);
priv_dev->gadget_driver = driver;
+
+ /* limit speed if necessary */
+ max_speed = min(driver->max_speed, gadget->max_speed);
+
+ switch (max_speed) {
+ case USB_SPEED_FULL:
+ writel(USB_CONF_SFORCE_FS, &priv_dev->regs->usb_conf);
+ writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);
+ break;
+ case USB_SPEED_HIGH:
+ writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);
+ break;
+ case USB_SPEED_SUPER:
+ break;
+ default:
+ dev_err(priv_dev->dev,
+ "invalid maximum_speed parameter %d\n",
+ max_speed);
+ /* fall through */
+ case USB_SPEED_UNKNOWN:
+ /* default to superspeed */
+ max_speed = USB_SPEED_SUPER;
+ break;
+ }

I had suggested some simplification for this case statement.


oops, looks like Greg picked this already.

During more tests today I just observed that this patch causes
the following regression.

Connect EVM to Super-Speed host
Load g_audio. (this enumerates as HS which is fine)
unload g_audio
load g_zero (this enumerates at HS instead of SS).

This is because the speed limit that we set doesn't get cleared.

Now the bits are write only and there is a way to undo USB_CONF_SFORCE_FS
by writing USB_CONF_CFORCE_FS, however there is no corresponding bit
to clear USB_CONF_USB3DIS. Only way seems to be USB_CFG_SWRST which
is a bit harsh IMO.

Pawel,

could you please confirm what is the best way to undo the high-speed
limit?

--
cheers,
-roger
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki