RE: [PATCH v2 7/9] crypto: ccp: Add support for ringing a platform doorbell

[Limonciello, Mario]

[Public]



> -----Original Message-----
> From: Lendacky, Thomas <Thomas.Lendacky@xxxxxxx>
> Sent: Thursday, March 2, 2023 15:52
> To: Limonciello, Mario <Mario.Limonciello@xxxxxxx>; Jan Dąbroś
> <jsd@xxxxxxxxxxxx>; Grzegorz Bernacki <gjb@xxxxxxxxxxxx>; Thomas, Rijo-
> john <Rijo-john.Thomas@xxxxxxx>; herbert@xxxxxxxxxxxxxxxxxxx; Allen,
> John <John.Allen@xxxxxxx>
> Cc: David S. Miller <davem@xxxxxxxxxxxxx>; linux-crypto@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 7/9] crypto: ccp: Add support for ringing a platform
> doorbell
> 
> On 3/2/23 13:42, Mario Limonciello wrote:
> > Some platforms support using a doorbell to communicate. Export
> > this feature for other drivers to utilize as well.
> >
> > Link: https://lore.kernel.org/linux-i2c/20220916131854.687371-3-
> jsd@xxxxxxxxxxxx/
> > Suggested-by: Jan Dabros <jsd@xxxxxxxxxxxx>
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > ---
> > v1->v2:
> >   * New patch
> > ---
> >   drivers/crypto/ccp/platform-access.c | 47
> ++++++++++++++++++++++++++++
> >   drivers/crypto/ccp/sp-dev.h          |  1 +
> >   include/linux/psp-platform-access.h  | 15 +++++++++
> >   include/linux/psp.h                  |  3 ++
> >   4 files changed, 66 insertions(+)
> >
> > diff --git a/drivers/crypto/ccp/platform-access.c
> b/drivers/crypto/ccp/platform-access.c
> > index af3a1e97abfe..0763389a2814 100644
> > --- a/drivers/crypto/ccp/platform-access.c
> > +++ b/drivers/crypto/ccp/platform-access.c
> > @@ -135,6 +135,53 @@ int psp_send_platform_access_msg(enum
> psp_platform_access_msg msg,
> >   }
> >   EXPORT_SYMBOL_GPL(psp_send_platform_access_msg);
> >
> > +int psp_ring_platform_doorbell(enum psp_platform_access_msg msg)
> > +{
> > +	struct psp_device *psp = psp_get_master_device();
> > +	struct psp_platform_access_device *pa_dev;
> > +	u32 __iomem *drbl;
> > +	u32 drbl_reg;
> 
> Lets spell out doorbell for these two variable names.

Ack.  Given drbl_reg is only used one place, I might just drop it too.

> 
> > +	int ret;
> > +
> > +	if (!psp || !psp->platform_access_data)
> > +		return -ENODEV;
> > +
> > +	pa_dev = psp->platform_access_data;
> > +	drbl = psp->io_regs + pa_dev->vdata->doorbell_reg;
> > +
> > +	if (!drbl)
> > +		return -ENODEV;
> 
> This will be non-zero because psp->io_regs will always be non-zero. Maybe
> you meant to check the actual pa_dev->vdata->doorbell_reg value?
> 
> I think you should squash this and patch #9 together so that patch #8 just
> works right away.

Ack, I'll squash them together.

> 
> > +
> > +	mutex_lock(&pa_dev->mutex);
> 
> Does the doorbell register operate independently from the other registers
> (C2PMSG_28 - C2PMSG_30)? If it does, you could probably just introduce a
> doorbell mutex.

It does work independently.  I'll add a second mutex.

> 
> > +
> > +	if (check_recovery(drbl)) {
> > +		dev_dbg(psp->dev, "in recovery\n");
> 
> Maybe a bit more info as to what is "in recovery" (that goes for patch #4,
> too) or just prefix it with "doorbell" (and "platform" in #4) since you
> now have duplicated messages.

Will add prefixes to make unique messages.

> 
> > +		ret = -EBUSY;
> > +		goto unlock;
> > +	}
> > +
> > +	if (wait_cmd(drbl)) {
> > +		dev_dbg(psp->dev, "not done processing command\n");
> 
> Ditto.
> 
> Thanks,
> Tom

Thanks for the new comments.

I'll wait on Jan and Grzegorz to confirm whether the new doorbell stuff works
on Skyrim or not to spin a v3.

> 
> > +		ret = -EBUSY;
> > +		goto unlock;
> > +	}
> > +
> > +	drbl_reg = FIELD_PREP(PSP_DRBL_MSG, msg) | PSP_DRBL_RING;
> > +	iowrite32(drbl_reg, drbl);
> > +
> > +	if (wait_cmd(drbl)) {
> > +		ret = -ETIMEDOUT;
> > +		goto unlock;
> > +	}
> > +
> > +	ret = 0;
> > +unlock:
> > +	mutex_unlock(&pa_dev->mutex);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(psp_ring_platform_doorbell);
> > +
> >   void platform_access_dev_destroy(struct psp_device *psp)
> >   {
> >   	struct psp_platform_access_device *pa_dev = psp-
> >platform_access_data;
> > diff --git a/drivers/crypto/ccp/sp-dev.h b/drivers/crypto/ccp/sp-dev.h
> > index 5ec6c219a731..87c0b9350bc2 100644
> > --- a/drivers/crypto/ccp/sp-dev.h
> > +++ b/drivers/crypto/ccp/sp-dev.h
> > @@ -54,6 +54,7 @@ struct tee_vdata {
> >   };
> >
> >   struct platform_access_vdata {
> > +	const unsigned int doorbell_reg;
> >   	const unsigned int cmdresp_reg;
> >   	const unsigned int cmdbuff_addr_lo_reg;
> >   	const unsigned int cmdbuff_addr_hi_reg;
> > diff --git a/include/linux/psp-platform-access.h b/include/linux/psp-
> platform-access.h
> > index f5a03cd11f10..1e1d0e077cec 100644
> > --- a/include/linux/psp-platform-access.h
> > +++ b/include/linux/psp-platform-access.h
> > @@ -35,6 +35,21 @@ struct psp_request {
> >    */
> >   int psp_send_platform_access_msg(enum psp_platform_access_msg,
> struct psp_request *req);
> >
> > +/**
> > + * psp_ring_platform_doorbell() - Ring platform doorbell
> > + *
> > + * This function is intended to be used by drivers outside of ccp to ring the
> > + * platform doorbell with a message.
> > + *
> > + * Returns:
> > + *  0:           success
> > + *  -%EBUSY:     mailbox in recovery or in use
> > + *  -%ENODEV:    driver not bound with PSP device
> > + *  -%ETIMEDOUT: request timed out
> > + *  -%EIO:       unknown error (see kernel log)
> > + */
> > +int psp_ring_platform_doorbell(enum psp_platform_access_msg);
> > +
> >   /**
> >    * psp_check_platform_access_status() - Checks whether platform
> features is ready
> >    *
> > diff --git a/include/linux/psp.h b/include/linux/psp.h
> > index d3424790a70e..92e60aeef21e 100644
> > --- a/include/linux/psp.h
> > +++ b/include/linux/psp.h
> > @@ -23,4 +23,7 @@
> >   #define PSP_CMDRESP_RECOVERY	BIT(30)
> >   #define PSP_CMDRESP_RESP	BIT(31)
> >
> > +#define PSP_DRBL_MSG		PSP_CMDRESP_CMD
> > +#define PSP_DRBL_RING		BIT(0)
> > +
> >   #endif /* __PSP_H */