From f0afba4042bd902d290405c0638bc1295872d8a7 Mon Sep 17 00:00:00 2001 From: Peijie Shao Date: Tue, 23 May 2023 10:45:36 +0800 Subject: [PATCH] tpm_tis_spi: Release chip select when flow control fails 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 Reviewed-by: Jarkko Sakkinen Signed-off-by: Jarkko Sakkinen --- drivers/char/tpm/tpm_tis_spi_main.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/char/tpm/tpm_tis_spi_main.c b/drivers/char/tpm/tpm_tis_spi_main.c index 1f52079..9bfaba0 100644 --- a/drivers/char/tpm/tpm_tis_spi_main.c +++ b/drivers/char/tpm/tpm_tis_spi_main.c @@ -136,6 +136,14 @@ int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len, } exit: + if (ret < 0) { + /* Deactivate chip select */ + memset(&spi_xfer, 0, sizeof(spi_xfer)); + spi_message_init(&m); + spi_message_add_tail(&spi_xfer, &m); + spi_sync_locked(phy->spi_device, &m); + } + spi_bus_unlock(phy->spi_device->master); return ret; } -- 2.7.4