mmc: cqhci: add cqhci_host_ops::program_key

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 1bc726e2 ("scsi: ufs: Add
program_key() variant op").
Acked-by: NAdrian Hunter <adrian.hunter@intel.com>
Reviewed-by: NSatya Tangirala <satyat@google.com>
Reviewed-and-tested-by: NPeng Zhou <peng.zhou@mediatek.com>
Signed-off-by: NEric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20210126001456.382989-6-ebiggers@kernel.orgSigned-off-by: NUlf Hansson <ulf.hansson@linaro.org>

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);
 }
 
 /*

drivers/mmc/host/cqhci.h

@@ -286,6 +286,10 @@ 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)