bus: mhi: host: Read PK HASH dynamically

The OEM PK HASH registers in the BHI region are read once during firmware
load (boot), cached, and displayed on demand via sysfs. This has a few
problems - if firmware load is skipped, the registers will not be read and
if the register values change over the life of the device the local cache
will be out of sync.

Qualcomm Cloud AI 100 can expose both these problems. It is possible for
mhi_async_power_up() to be invoked while the device is in AMSS EE, which
would bypass firmware loading. Also, Qualcomm Cloud AI 100 has 5 PK HASH
slots which can be dynamically provisioned while the device is active,
which would result in the values changing and users may want to know what
keys are active.

Address these concerns by reading the PK HASH registers on-demand during
the sysfs read. This will result in showing the most current information.

Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@quicinc.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20240105174253.863388-1-quic_jhugo@quicinc.com
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

2 files changed, 13 insertions, 14 deletions

diff --git a/drivers/bus/mhi/host/boot.c b/drivers/bus/mhi/host/boot.c
index edc0ec5a0933..dedd29ca8db3 100644
--- a/drivers/bus/mhi/host/boot.c
+++ b/drivers/bus/mhi/host/boot.c
@@ -395,7 +395,7 @@ void mhi_fw_load_handler(struct mhi_controller *mhi_cntrl)
 	void *buf;
 	dma_addr_t dma_addr;
 	size_t size, fw_sz;
-	int i, ret;
+	int ret;
 
 	if (MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)) {
 		dev_err(dev, "Device MHI is not in valid state\n");
@@ -408,15 +408,6 @@ void mhi_fw_load_handler(struct mhi_controller *mhi_cntrl)
 	if (ret)
 		dev_err(dev, "Could not capture serial number via BHI\n");
 
-	for (i = 0; i < ARRAY_SIZE(mhi_cntrl->oem_pk_hash); i++) {
-		ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->bhi, BHI_OEMPKHASH(i),
-				   &mhi_cntrl->oem_pk_hash[i]);
-		if (ret) {
-			dev_err(dev, "Could not capture OEM PK HASH via BHI\n");
-			break;
-		}
-	}
-
 	/* wait for ready on pass through or any other execution environment */
 	if (!MHI_FW_LOAD_CAPABLE(mhi_cntrl->ee))
 		goto fw_load_ready_state;
diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index 8e5ec1a409b8..6d3b045ab259 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -98,11 +98,19 @@ static ssize_t oem_pk_hash_show(struct device *dev,
 {
 	struct mhi_device *mhi_dev = to_mhi_device(dev);
 	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
-	int i, cnt = 0;
+	u32 hash_segment[MHI_MAX_OEM_PK_HASH_SEGMENTS];
+	int i, cnt = 0, ret;
 
-	for (i = 0; i < ARRAY_SIZE(mhi_cntrl->oem_pk_hash); i++)
-		cnt += sysfs_emit_at(buf, cnt, "OEMPKHASH[%d]: 0x%x\n",
-				i, mhi_cntrl->oem_pk_hash[i]);
+	for (i = 0; i < MHI_MAX_OEM_PK_HASH_SEGMENTS; i++) {
+		ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->bhi, BHI_OEMPKHASH(i), &hash_segment[i]);
+		if (ret) {
+			dev_err(dev, "Could not capture OEM PK HASH\n");
+			return ret;
+		}
+	}
+
+	for (i = 0; i < MHI_MAX_OEM_PK_HASH_SEGMENTS; i++)
+		cnt += sysfs_emit_at(buf, cnt, "OEMPKHASH[%d]: 0x%x\n", i, hash_segment[i]);
 
 	return cnt;
 }