Platforms supporting direct message request v2 [1] can support secure partitions that support multiple services. For CRB over FF-A interface, if the firmware TPM or TPM service [1] shares its Secure Partition (SP) with another service, message requests may fail with a -EBUSY error.
To handle this, replace the single check and call with a retry loop that attempts the TPM message send operation until it succeeds or a configurable timeout is reached. The retry mechanism introduces a module parameter (`busy_timeout_ms`, default: 2000ms) to control how long to keep retrying on -EBUSY responses. Between retries, the code waits briefly (50-100 microseconds) to avoid busy-waiting and handling TPM BUSY conditions more gracefully. The parameter can be modified at run-time as such: echo 3000 | tee /sys/module/tpm_crb_ffa/parameters/busy_timeout_ms This changes the timeout from the default 2000ms to 3000ms. [1] TPM Service Command Response Buffer Interface Over FF-A https://developer.arm.com/documentation/den0138/latest/ Signed-off-by: Prachotan Bathi <prachotan.ba...@arm.com> --- drivers/char/tpm/tpm_crb_ffa.c | 77 +++++++++++++++++++++++----------- 1 file changed, 53 insertions(+), 24 deletions(-) diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c index 4ead61f01299..19de2dda75de 100644 --- a/drivers/char/tpm/tpm_crb_ffa.c +++ b/drivers/char/tpm/tpm_crb_ffa.c @@ -10,6 +10,8 @@ #define pr_fmt(fmt) "CRB_FFA: " fmt #include <linux/arm_ffa.h> +#include <linux/delay.h> +#include <linux/moduleparam.h> #include "tpm_crb_ffa.h" /* TPM service function status codes */ @@ -178,6 +180,17 @@ int tpm_crb_ffa_init(void) } EXPORT_SYMBOL_GPL(tpm_crb_ffa_init); +static unsigned int busy_timeout_ms = 2000; +/** + * busy_timeout_ms - Maximum time to retry before giving up on busy + * + * This parameter defines the maximum time in milliseconds to retry + * sending a message to the TPM service before giving up. + */ +module_param(busy_timeout_ms, uint, 0644); +MODULE_PARM_DESC(busy_timeout_ms, + "Maximum time(in ms) to retry before giving up on busy"); + static int __tpm_crb_ffa_send_recieve(unsigned long func_id, unsigned long a0, unsigned long a1, @@ -191,34 +204,50 @@ static int __tpm_crb_ffa_send_recieve(unsigned long func_id, msg_ops = tpm_crb_ffa->ffa_dev->ops->msg_ops; - if (ffa_partition_supports_direct_req2_recv(tpm_crb_ffa->ffa_dev)) { - memset(&tpm_crb_ffa->direct_msg_data2, 0x00, - sizeof(struct ffa_send_direct_data2)); + ktime_t start; + ktime_t stop; + + start = ktime_get(); + stop = ktime_add(start, ms_to_ktime(busy_timeout_ms)); + + do { + if (ffa_partition_supports_direct_req2_recv(tpm_crb_ffa->ffa_dev)) { + memset(&tpm_crb_ffa->direct_msg_data2, 0x00, + sizeof(struct ffa_send_direct_data2)); - tpm_crb_ffa->direct_msg_data2.data[0] = func_id; - tpm_crb_ffa->direct_msg_data2.data[1] = a0; - tpm_crb_ffa->direct_msg_data2.data[2] = a1; - tpm_crb_ffa->direct_msg_data2.data[3] = a2; + tpm_crb_ffa->direct_msg_data2.data[0] = func_id; + tpm_crb_ffa->direct_msg_data2.data[1] = a0; + tpm_crb_ffa->direct_msg_data2.data[2] = a1; + tpm_crb_ffa->direct_msg_data2.data[3] = a2; - ret = msg_ops->sync_send_receive2(tpm_crb_ffa->ffa_dev, + ret = msg_ops->sync_send_receive2(tpm_crb_ffa->ffa_dev, &tpm_crb_ffa->direct_msg_data2); - if (!ret) - ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data2.data[0]); - } else { - memset(&tpm_crb_ffa->direct_msg_data, 0x00, - sizeof(struct ffa_send_direct_data)); - - tpm_crb_ffa->direct_msg_data.data1 = func_id; - tpm_crb_ffa->direct_msg_data.data2 = a0; - tpm_crb_ffa->direct_msg_data.data3 = a1; - tpm_crb_ffa->direct_msg_data.data4 = a2; - - ret = msg_ops->sync_send_receive(tpm_crb_ffa->ffa_dev, - &tpm_crb_ffa->direct_msg_data); - if (!ret) - ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1); - } + if (!ret) + ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data2.data[0]); + } else { + memset(&tpm_crb_ffa->direct_msg_data, 0x00, + sizeof(struct ffa_send_direct_data)); + tpm_crb_ffa->direct_msg_data.data1 = func_id; + tpm_crb_ffa->direct_msg_data.data2 = a0; + tpm_crb_ffa->direct_msg_data.data3 = a1; + tpm_crb_ffa->direct_msg_data.data4 = a2; + + ret = msg_ops->sync_send_receive(tpm_crb_ffa->ffa_dev, + &tpm_crb_ffa->direct_msg_data); + if (!ret) + ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1); + } + if (ret == -EBUSY) + pr_err("TPM says busy, trying again, value, ret: %d\n", + ret); + else + break; + usleep_range(50, 100); + if (ktime_after(ktime_get(), stop)) + dev_warn(&tpm_crb_ffa->ffa_dev->dev, "Busy retry timed out\n"); + + } while (ktime_before(ktime_get(), stop)); return ret; } -- 2.43.0
