[v2,5/9] mmc: cqhci: add cqhci_host_ops::program_key

From: Eric Biggers <ebiggers@google.com>

On Snapdragon SoCs, the Linux kernel isn't permitted to directly access
the standard CQHCI crypto configuration registers.  Instead, programming
and evicting keys must be done through vendor-specific SMC calls.

To support this hardware, add a ->program_key() method to
'struct cqhci_host_ops'.  This allows overriding the standard CQHCI
crypto key programming / eviction procedure.

This is inspired by the corresponding UFS crypto support, which uses
these same SMC calls.  See commit 1bc726e26ef3 ("scsi: ufs: Add
program_key() variant op").

Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 drivers/mmc/host/cqhci-crypto.c | 22 +++++++++++++---------
 drivers/mmc/host/cqhci.h        |  4 ++++
 2 files changed, 17 insertions(+), 9 deletions(-)

On Wed, Dec 02, 2020 at 06:05:12PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> On Snapdragon SoCs, the Linux kernel isn't permitted to directly access
> the standard CQHCI crypto configuration registers.  Instead, programming
> and evicting keys must be done through vendor-specific SMC calls.
> 
> To support this hardware, add a ->program_key() method to
> 'struct cqhci_host_ops'.  This allows overriding the standard CQHCI
> crypto key programming / eviction procedure.
> 
> This is inspired by the corresponding UFS crypto support, which uses
> these same SMC calls.  See commit 1bc726e26ef3 ("scsi: ufs: Add
> program_key() variant op").
> 
> Acked-by: Adrian Hunter <adrian.hunter@intel.com>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  drivers/mmc/host/cqhci-crypto.c | 22 +++++++++++++---------
>  drivers/mmc/host/cqhci.h        |  4 ++++
>  2 files changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/mmc/host/cqhci-crypto.c b/drivers/mmc/host/cqhci-crypto.c
> index 98f141c8480ce..0aaa948d240b1 100644
> --- a/drivers/mmc/host/cqhci-crypto.c
> +++ b/drivers/mmc/host/cqhci-crypto.c
> @@ -30,13 +30,16 @@ cqhci_host_from_ksm(struct blk_keyslot_manager *ksm)
>  	return mmc->cqe_private;
>  }
>  
> -static void cqhci_crypto_program_key(struct cqhci_host *cq_host,
> -				     const union cqhci_crypto_cfg_entry *cfg,
> -				     int slot)
> +static int cqhci_crypto_program_key(struct cqhci_host *cq_host,
> +				    const union cqhci_crypto_cfg_entry *cfg,
> +				    int slot)
>  {
>  	u32 slot_offset = cq_host->crypto_cfg_register + slot * sizeof(*cfg);
>  	int i;
>  
> +	if (cq_host->ops->program_key)
> +		return cq_host->ops->program_key(cq_host, cfg, slot);
> +
>  	/* Clear CFGE */
>  	cqhci_writel(cq_host, 0, slot_offset + 16 * sizeof(cfg->reg_val[0]));
>  
> @@ -51,6 +54,7 @@ static void cqhci_crypto_program_key(struct cqhci_host *cq_host,
>  	/* Write dword 16, which includes the new value of CFGE */
>  	cqhci_writel(cq_host, le32_to_cpu(cfg->reg_val[16]),
>  		     slot_offset + 16 * sizeof(cfg->reg_val[0]));
> +	return 0;
>  }
>  
>  static int cqhci_crypto_keyslot_program(struct blk_keyslot_manager *ksm,
> @@ -67,6 +71,7 @@ static int cqhci_crypto_keyslot_program(struct blk_keyslot_manager *ksm,
>  	int i;
>  	int cap_idx = -1;
>  	union cqhci_crypto_cfg_entry cfg = {};
> +	int err;
>  
>  	BUILD_BUG_ON(CQHCI_CRYPTO_KEY_SIZE_INVALID != 0);
>  	for (i = 0; i < cq_host->crypto_capabilities.num_crypto_cap; i++) {
> @@ -93,13 +98,13 @@ static int cqhci_crypto_keyslot_program(struct blk_keyslot_manager *ksm,
>  		memcpy(cfg.crypto_key, key->raw, key->size);
>  	}
>  
> -	cqhci_crypto_program_key(cq_host, &cfg, slot);
> +	err = cqhci_crypto_program_key(cq_host, &cfg, slot);
>  
>  	memzero_explicit(&cfg, sizeof(cfg));
> -	return 0;
> +	return err;
>  }
>  
> -static void cqhci_crypto_clear_keyslot(struct cqhci_host *cq_host, int slot)
> +static int cqhci_crypto_clear_keyslot(struct cqhci_host *cq_host, int slot)
>  {
>  	/*
>  	 * Clear the crypto cfg on the device. Clearing CFGE
> @@ -107,7 +112,7 @@ static void cqhci_crypto_clear_keyslot(struct cqhci_host *cq_host, int slot)
>  	 */
>  	union cqhci_crypto_cfg_entry cfg = {};
>  
> -	cqhci_crypto_program_key(cq_host, &cfg, slot);
> +	return cqhci_crypto_program_key(cq_host, &cfg, slot);
>  }
>  
>  static int cqhci_crypto_keyslot_evict(struct blk_keyslot_manager *ksm,
> @@ -116,8 +121,7 @@ static int cqhci_crypto_keyslot_evict(struct blk_keyslot_manager *ksm,
>  {
>  	struct cqhci_host *cq_host = cqhci_host_from_ksm(ksm);
>  
> -	cqhci_crypto_clear_keyslot(cq_host, slot);
> -	return 0;
> +	return cqhci_crypto_clear_keyslot(cq_host, slot);
>  }
>  
>  /*
> diff --git a/drivers/mmc/host/cqhci.h b/drivers/mmc/host/cqhci.h
> index 5c18734624fea..ece997dd8bcc7 100644
> --- a/drivers/mmc/host/cqhci.h
> +++ b/drivers/mmc/host/cqhci.h
> @@ -287,6 +287,10 @@ struct cqhci_host_ops {
>  				 u64 *data);
>  	void (*pre_enable)(struct mmc_host *mmc);
>  	void (*post_disable)(struct mmc_host *mmc);
> +#ifdef CONFIG_MMC_CRYPTO
> +	int (*program_key)(struct cqhci_host *cq_host,
> +			   const union cqhci_crypto_cfg_entry *cfg, int slot);
> +#endif
>  };
>  
>  static inline void cqhci_writel(struct cqhci_host *host, u32 val, int reg)
> -- 
> 2.29.2
> 
Looks good to me. Please feel free to add
Reviewed-by: Satya Tangirala <satyat@google.com>