linux-kernel - Re: [PATCH v5 3/3] i2c: designware: Add doorbell support for Mendocino

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Message-ID: <CANg-bXANgkrF4T4X_VgeVejA2wH3GrUiFORyRC4AZfgYrE+7DQ@mail.gmail.com>
Date:   Wed, 22 Mar 2023 11:01:44 -0600
From:   Mark Hasemeyer <markhas@...omium.org>
To:     Mario Limonciello <mario.limonciello@....com>
Cc:     Grzegorz Bernacki <gjb@...ihalf.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jan Dabros <jsd@...ihalf.com>, Held Felix <Felix.Held@....com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/3] i2c: designware: Add doorbell support for Mendocino

> +static int psp_send_i2c_req_mendocino(enum psp_i2c_req_type i2c_req_type)
> +{
> +       int status, ret;
> +
> +       ret = read_poll_timeout(psp_ring_platform_doorbell, status,
> +                               (status != -EBUSY),
> +                               PSP_I2C_REQ_RETRY_DELAY_US,
> +                               PSP_I2C_REQ_RETRY_CNT * PSP_I2C_REQ_RETRY_DELAY_US,
> +                               0, i2c_req_type);
> +       if (ret)
> +               dev_err(psp_i2c_dev, "Timed out waiting for PSP to %s I2C bus\n",
> +                       (i2c_req_type == PSP_I2C_REQ_ACQUIRE) ?
> +                       "release" : "acquire");
> +
> +       return ret ? ret : status;
> +}

I think we need the value of the PSP_CMDRESP_STS field returned to the caller
and its status checked like in psp_send_i2c_req_cezanne. Otherwise the function
won't continue to poll when the PSP_I2C_REQ_STS_BUS_BUSY bit is set.

FYI - there's a test on ChromeOS to stress test I2C bus arbitration:
https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/platform/tast-tests/src/chromiumos/tast/local/bundles/cros/hwsec/tpm_contest.go
I can try to run it assuming the ToT kernel runs on skyrim.