linux-kernel - Re: question about setting TPM_CHIP_FLAG_IRQ in tpm_tis_core

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Date:   Tue, 12 Nov 2019 07:24:18 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     Stefan Berger <stefanb@...ux.ibm.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: question about setting TPM_CHIP_FLAG_IRQ in tpm_tis_core_init

On Tue Nov 12 19, Stefan Berger wrote:
>On 11/11/19 10:36 PM, Jerry Snitselaar wrote:
>>Question about 1ea32c83c699 ("tpm_tis_core: Set TPM_CHIP_FLAG_IRQ 
>>before probing for interrupts").
>>Doesn't tpm_tis_send set this flag, and setting it here in 
>>tpm_tis_core_init short circuits what
>>tpm_tis_send was doing before? There is a bug report of an interrupt 
>>storm from a tpm on a t490s laptop
>>with the Fedora 31 kernel (5.3), and I'm wondering if this change 
>>could cause that. Before they got
>>the warning about interrupts not working, and using polling instead.
>>
>I set this flag for the TIS because it wasn't set anywhere else. 
>tpm_tis_send() wouldn't set the flag but go via the path:
>
>if (!(chip->flags & TPM_CHIP_FLAG_IRQ) || priv->irq_tested)
>
>        return tpm_tis_send_main(chip, buf, len);
>
>the only other line for the TIS to set the IRQ flag was in the same 
>function further below, though that wouldn't be reached due to the 
>above:
>
>[...]
>
>priv->irq = irq;
>
>chip->flags |= TPM_CHIP_FLAG_IRQ;
>
>
>   Stefan
>
>

Ugh, you're right I was reading that as ! around both the flag and priv->irq_tested.

Should the flag be cleared if tpm_tis_probe_irq_single fails prior to calling
tpm_tis_gen_interrupt?