Re: [PATCH] bus: mhi: host: Read PK HASH dynamically

[Manivannan Sadhasivam <mani@kernel.org>]

On Fri, Dec 08, 2023 at 09:59:38AM -0700, Jeffrey Hugo wrote:
> 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>
> ---
>  drivers/bus/mhi/host/boot.c | 11 +----------
>  drivers/bus/mhi/host/init.c | 16 ++++++++++++----
>  include/linux/mhi.h         |  2 --
>  3 files changed, 13 insertions(+), 16 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 65ceac1837f9..e2c2f510b04f 100644
> --- a/drivers/bus/mhi/host/init.c
> +++ b/drivers/bus/mhi/host/init.c
> @@ -97,11 +97,19 @@ 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 cnt;

return ret?

- Mani

> +		}
> +	}
> +
> +	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;
>  }
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index d0f9b522f328..474d32cb0520 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -325,7 +325,6 @@ struct mhi_controller_config {
>   * @major_version: MHI controller major revision number
>   * @minor_version: MHI controller minor revision number
>   * @serial_number: MHI controller serial number obtained from BHI
> - * @oem_pk_hash: MHI controller OEM PK Hash obtained from BHI
>   * @mhi_event: MHI event ring configurations table
>   * @mhi_cmd: MHI command ring configurations table
>   * @mhi_ctxt: MHI device context, shared memory between host and device
> @@ -413,7 +412,6 @@ struct mhi_controller {
>  	u32 major_version;
>  	u32 minor_version;
>  	u32 serial_number;
> -	u32 oem_pk_hash[MHI_MAX_OEM_PK_HASH_SEGMENTS];
>  
>  	struct mhi_event *mhi_event;
>  	struct mhi_cmd *mhi_cmd;
> -- 
> 2.34.1
> 
> 

-- 
மணிவண்ணன் சதாசிவம்