tpm_tis_spi: Release chip select when flow control fails

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The failure paths in tpm_tis_spi_transfer() do not deactivate
chip select. Send an empty message (cs_select == 0) to overcome
this.

The patch is tested by two ways.
One way needs to touch hardware:
   1. force pull MISO pin down to GND, it emulates a forever
      'WAIT' timing.
   2. probe cs pin by an oscilloscope.
   3. load tpm_tis_spi.ko.
After loading, dmesg prints:
    "probe of spi0.0 failed with error -110"
and oscilloscope shows cs pin goes high(deactivated) after
the failure. Before the patch, cs pin keeps low.

Second way is by writing a fake spi controller.
   1. implement .transfer_one method, fill all rx buf with 0.
   2. implement .set_cs method, print the state of cs pin.
   we can see cs goes high after the failure.

Signed-off-by: Peijie Shao <shaopeijie@cestc.cn>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

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Peijie Shao 2023-05-23 10:45:36 +08:00 • committed by Jarkko Sakkinen

parent edb13d7bb0

commit f0afba4042

1 changed files with 8 additions and 0 deletions

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drivers/char/tpm/tpm_tis_spi_main.c

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