On Wed, May 28, 2025 at 05:34:49PM +0800, Qunqin Zhao wrote:
在 2025/5/28 下午5:24, Qunqin Zhao 写道:
在 2025/5/28 下午5:00, Stefano Garzarella 写道:
On Wed, May 28, 2025 at 04:42:05PM +0800, Qunqin Zhao wrote:
在 2025/5/28 下午3:57, Stefano Garzarella 写道:
+ chip = tpmm_chip_alloc(dev, &tpm_loongson_ops);
+ if (IS_ERR(chip))
+ return PTR_ERR(chip);
+ chip->flags = TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_IRQ;
Why setting TPM_CHIP_FLAG_IRQ?
When tpm_engine completes TPM_CC* command,
the hardware will indeed trigger an interrupt to the kernel.
IIUC that is hidden by loongson_se_send_engine_cmd(), that for
this driver is completely synchronous, no?
IIUC this driver is similar to ftpm and svsm where the send is
synchronous so having .status, .cancel, etc. set to 0 should
be enough to call .recv() just after send() in
tpm_try_transmit(). See commit 980a573621ea ("tpm: Make
chip->{status,cancel,req_canceled} opt")
The send callback would wait until the TPM_CC* command complete.
We don't need a poll.
Right, that's what I was saying too, send() is synchronous (as in
ftpm and svsm). The polling in tpm_try_transmit() is already
skipped since we are setting .status = 0, .req_complete_mask = 0,
.req_complete_val = 0, etc. so IMHO this is exactly the same of
ftpm and svsm, so we don't need to set TPM_CHIP_FLAG_IRQ.
I see, but why not skip polling directly in "if (chip->flags &
TPM_CHIP_FLAG_IRQ)" instead of do while?
I mean, why not skip polling directly in "if (chip->flags &
TPM_CHIP_FLAG_IRQ)"?
And In my opinion, TPM_CHIP_FLAG_SYNC and TPM_CHIP_FLAG_IRQ are
essentially the same, only with different names.
When TPM_CHIP_FLAG_SYNC is defined, the .recv() is not invoked and
.send() will send the command and retrieve the response. For some driver
like ftpm this will save an extra copy/buffer.
Stefano
