Re: [tpmdd-devel] [PATCH 13/16] tpm/tpm_i2c_stm_st33: Add tpm_lock mutex for safe irq management

Hi Jason,

Here i want to prevent a TPM TIS write command sent when a TPM TIS read 
command is on going on the bus.
Basically:
- a TPM TIS write looks like the following format: <W reg data>
- a TPM TIS read looks like the following format: <W reg dummy><R data>

If an interrupt occur a TPM TIS read might be interrupted by a TPM TIS 
write to clear the pending interrupt giving potentially something like that:
<W reg dummy><W reg data> <R data>
The TPM behavior in this situation is unknown...

Best Regards
Christophe
On 07/10/2014 23:56, Jason Gunthorpe wrote:

On Tue, Oct 07, 2014 at 10:03:06PM +0200, Christophe Ricard wrote:

quoted

Adding tpm_lock mutex in order to guarantee that a i2c_read_data or a
i2c_write_data will not get interrupted by a threaded interrupt.

Can you elaborate on this?

Any call from the TPM core itself through 'ops' is locked already, and
I don't see this driver's IRQ handler doing I2C ops..

What scenario is this protecting against?

Jason

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