linux-kernel - Re: [PATCH v2 7/9] crypto: ccp: Add support for ringing a platform doorbell

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Message-ID: <b52c68e6-2501-67c8-1fbd-60a35537c1f2@amd.com>
Date:   Thu, 2 Mar 2023 15:51:46 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Mario Limonciello <mario.limonciello@....com>,
        Jan Dąbroś <jsd@...ihalf.com>,
        Grzegorz Bernacki <gjb@...ihalf.com>, Rijo-john.Thomas@....com,
        herbert@...dor.apana.org.au, John Allen <john.allen@....com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
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@semihalf.com/
> Suggested-by: Jan Dabros <jsd@...ihalf.com>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> 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.

> +	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.

> +
> +	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.

> +
> +	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.

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

Ditto.

Thanks,
Tom

> +		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 */