linux-kernel - [PATCH v2 0/1] tpm_crb_ffa: handle tpm busy return code

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Message-ID: <20250610213505.3881352-1-prachotan.bathi@arm.com>
Date: Tue, 10 Jun 2025 16:35:04 -0500
From: Prachotan Bathi <prachotan.bathi@....com>
To: Peter Huewe <peterhuewe@....de>,
	Jarkko Sakkinen <jarkko@...nel.org>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Stuart Yoder <stuart.yoder@....com>
Cc: linux-integrity@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Prachotan Bathi <prachotan.bathi@....com>
Subject: [PATCH v2 0/1] tpm_crb_ffa: handle tpm busy return code

Platforms supporting direct message request v2 can
support SPs that support multiple services.
If the TPM service is sharing the SP with another service,
it could get an error code of BUSY if the other service is
in process.
We need a way for the driver to retry sending the message
to the TPM service until it succeeds or we know that no forward progress
can be made.
This adds a parameterized variable (default 2000ms)
that indicates the maximum time to keep retrying for.

This is building on top of commit a85b55ee64a5da58c6e2c69e2648023189210eae.
A tpm service can be accessed by the driver using direct message request v2 
interface according to chapter 3.3, TPM Service Command Response Buffer 
Interface Over FF-A specificationi v1.0 EAC.

Prachotan Bathi (1):
  tpm_crb_ffa: handle tpm busy return code

 drivers/char/tpm/tpm_crb_ffa.c | 78 +++++++++++++++++++++++-----------
 1 file changed, 54 insertions(+), 24 deletions(-)

-- 
2.43.0