linux-kernel - Re: [PATCH v2] tpm_tis_spi: fix:release chip select when flow control fails

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Message-ID: <7840f8c2-a903-7d80-c4bd-8568ad1c8682@molgen.mpg.de>
Date:   Mon, 22 May 2023 10:17:42 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Peijie Shao <shaopeijie@...tc.cn>
Cc:     jarkko@...nel.org, peterhuewe@....de, jgg@...pe.ca,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] tpm_tis_spi: fix:release chip select when flow control
 fails

Dear Peijie,


Thank you for your patch.

The fix: tag in your commit message summary is uncommon. I suggest:

> tpm_tis_spi: Release chip select when flow control fails


Am 22.05.23 um 09:01 schrieb shaopeijie@...tc.cn:
> From: Peijie Shao <shaopeijie@...tc.cn>
> 
> The failure paths in tpm_tis_spi_transfer() do not deactivate
> chip select. Send an empty message (cs_select == 0) to overcome
> this.

Does the standard require to deactivate it?

A note on your test setup would be nice to have in the commit message.

> Signed-off-by: Peijie Shao <shaopeijie@...tc.cn>
> ---
> Changes since v1:
>      1. Deactive cs all of the failure path, not only flow control.

Deactivate


Kind regards,

Paul


>      2. change and update comments.
> ---
>   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 1f5207974..9bfaba092 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;
>   }