[Linux-stm32] [PATCH v2 6/7] usb: typec: ucsi: extract common code for command handling

[Dmitry Baryshkov]

On Tue, Jun 25, 2024 at 05:24:54PM GMT, Fabrice Gasnier wrote:
> On 6/21/24 00:55, Dmitry Baryshkov wrote:
> > Extract common functions to handle command sending and to handle events
> > from UCSI. This ensures that all UCSI glue drivers handle the ACKs in
> > the same way.
> > 
> > The CCG driver used DEV_CMD_PENDING both for internal
> > firmware-related commands and for UCSI control handling. Leave the
> > former use case intact.
> > 
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> > ---
> >  drivers/usb/typec/ucsi/ucsi.c           | 43 +++++++++++++++++++++++++++
> >  drivers/usb/typec/ucsi/ucsi.h           |  7 +++++
> >  drivers/usb/typec/ucsi/ucsi_acpi.c      | 46 ++---------------------------
> >  drivers/usb/typec/ucsi/ucsi_ccg.c       | 21 ++-----------
> >  drivers/usb/typec/ucsi/ucsi_glink.c     | 47 ++---------------------------
> >  drivers/usb/typec/ucsi/ucsi_stm32g0.c   | 44 ++--------------------------
> >  drivers/usb/typec/ucsi/ucsi_yoga_c630.c | 52 ++-------------------------------
> >  7 files changed, 62 insertions(+), 198 deletions(-)
> > 
> > diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> > index 4ba22323dbf9..691ee0c4ef87 100644
> > --- a/drivers/usb/typec/ucsi/ucsi.c
> > +++ b/drivers/usb/typec/ucsi/ucsi.c
> > @@ -36,6 +36,48 @@
> >   */
> >  #define UCSI_SWAP_TIMEOUT_MS	5000
> >  
> > +void ucsi_notify_common(struct ucsi *ucsi, u32 cci)
> > +{
> > +	if (UCSI_CCI_CONNECTOR(cci))
> > +		ucsi_connector_change(ucsi, UCSI_CCI_CONNECTOR(cci));
> > +
> > +	if (cci & UCSI_CCI_ACK_COMPLETE &&
> > +	    test_bit(ACK_PENDING, &ucsi->flags))
> > +		complete(&ucsi->complete);
> > +
> > +	if (cci & UCSI_CCI_COMMAND_COMPLETE &&
> > +	    test_bit(COMMAND_PENDING, &ucsi->flags))
> > +		complete(&ucsi->complete);
> 
> Hi Dmitry,
> 
> I've recently faced some race with ucsi_stm32g0 driver, and have sent a
> fix for it [1], as you've noticed in the cover letter.
> 
> To fix that, I've used test_and_clear_bit() in above two cases, instead
> of test_bit().

Could you possible describe, why do you need test_and_clear_bit()
instead of just test_bit()? The bits are cleared at the end of the
.sync_write(), also there can be no other command (or ACK_CC) submission
before this one is fully processed.

> 
> https://lore.kernel.org/linux-usb/20240612124656.2305603-1-fabrice.gasnier@foss.st.com/
> 
> > +}
> > +EXPORT_SYMBOL_GPL(ucsi_notify_common);
> > +
> > +int ucsi_sync_control_common(struct ucsi *ucsi, u64 command)
> > +{
> > +	bool ack = UCSI_COMMAND(command) == UCSI_ACK_CC_CI;
> > +	int ret;
> > +
> > +	if (ack)
> > +		set_bit(ACK_PENDING, &ucsi->flags);
> > +	else
> > +		set_bit(COMMAND_PENDING, &ucsi->flags);
> > +
> > +	ret = ucsi->ops->async_control(ucsi, command);
> > +	if (ret)
> > +		goto out_clear_bit;
> > +
> > +	if (!wait_for_completion_timeout(&ucsi->complete, 5 * HZ))
> > +		ret = -ETIMEDOUT;
> 
> With test_and_clear_bit(), could return 0, in case of success here.

Oh, I see. So your code returns earlier. I have a feeling that this
approach is less logical and slightly harder to follow.

Maybe it's easier if it is implemented as:

if (wait_for_completion_timeout(...))
	return 0;

if (ack)
	clear_bit(ACK_PENDING)
else
	clear_bit(COMMAND_PENDING)

return -ETIMEDOUT;


OR

if (!wait_for_completion_timeout(...)) {
	if (ack)
		clear_bit(ACK_PENDING)
	else
		clear_bit(COMMAND_PENDING)

	return -ETIMEDOUT;
}

return 0;

But really, unless there is an actual issue with the current code, I'd
prefer to keep it. It makes it clear that the bits are set and then are
cleared properly.

> I'd suggest to use similar approach here, unless you see some drawback?
> 
> Best Regards,
> Fabrice
> 
> > +
> > +out_clear_bit:
> > +	if (ack)
> > +		clear_bit(ACK_PENDING, &ucsi->flags);
> > +	else
> > +		clear_bit(COMMAND_PENDING, &ucsi->flags);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(ucsi_sync_control_common);
> > +
> >  static int ucsi_acknowledge(struct ucsi *ucsi, bool conn_ack)
> >  {
> >  	u64 ctrl;
> > @@ -1883,6 +1925,7 @@ struct ucsi *ucsi_create(struct device *dev, const struct ucsi_operations *ops)
> >  	INIT_WORK(&ucsi->resume_work, ucsi_resume_work);
> >  	INIT_DELAYED_WORK(&ucsi->work, ucsi_init_work);
> >  	mutex_init(&ucsi->ppm_lock);
> > +	init_completion(&ucsi->complete);
> >  	ucsi->dev = dev;
> >  	ucsi->ops = ops;
> 
> [snip]
> 
> >  	ucsi->ucsi = ucsi_create(dev, &pmic_glink_ucsi_ops);
> > diff --git a/drivers/usb/typec/ucsi/ucsi_stm32g0.c b/drivers/usb/typec/ucsi/ucsi_stm32g0.c
> > index 14737ca3724c..d948c3f579e1 100644
> > --- a/drivers/usb/typec/ucsi/ucsi_stm32g0.c
> > +++ b/drivers/usb/typec/ucsi/ucsi_stm32g0.c
> > @@ -61,11 +61,7 @@ struct ucsi_stm32g0 {
> 
> [snip]
> 
> > -
> > -	ret = ucsi_stm32g0_async_control(ucsi, command);
> > -	if (ret)
> > -		goto out_clear_bit;
> > -
> > -	if (!wait_for_completion_timeout(&g0->complete, msecs_to_jiffies(5000)))
> > -		ret = -ETIMEDOUT;
> > -	else
> > -		return 0;
> > -
> > -out_clear_bit:
> > -	if (ack)
> > -		clear_bit(ACK_PENDING, &g0->flags);
> > -	else
> > -		clear_bit(COMMAND_PENDING, &g0->flags);
> > -
> > -	return ret;
> > -}
> > -
> >  static irqreturn_t ucsi_stm32g0_irq_handler(int irq, void *data)
> >  {
> >  	struct ucsi_stm32g0 *g0 = data;
> > @@ -449,13 +416,7 @@ static irqreturn_t ucsi_stm32g0_irq_handler(int irq, void *data)
> >  	if (ret)
> >  		return IRQ_NONE;
> >  
> > -	if (UCSI_CCI_CONNECTOR(cci))
> > -		ucsi_connector_change(g0->ucsi, UCSI_CCI_CONNECTOR(cci));
> > -
> > -	if (cci & UCSI_CCI_ACK_COMPLETE && test_and_clear_bit(ACK_PENDING, &g0->flags))
> > -		complete(&g0->complete);
> > -	if (cci & UCSI_CCI_COMMAND_COMPLETE && test_and_clear_bit(COMMAND_PENDING, &g0->flags))
> > -		complete(&g0->complete);
> > +	ucsi_notify_common(g0->ucsi, cci);
> 
> I can see the fix "test_and_clear_bit()" sent earlier is removed from here.
> 
> I'd suggest to use similar approach as here, unless you see some drawback?
> 
> Please advise,
> Best Regards,
> Fabrice

-- 
With best wishes
Dmitry