Message-ID: <07b78baf-e9d2-b4c3-5fe9-01f1b57033ab@amd.com>
Date:   Sun, 19 Mar 2023 19:16:49 -0500
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Subject: Re: [PATCH -next 2/2] i2c: designware: Add support for new SoCs in
 AMDPSP driver
Content-Language: en-US
To:     Mark Hasemeyer <markhas@chromium.org>, jsd@semihalf.com
Cc:     andriy.shevchenko@linux.intel.com, jarkko.nikula@linux.intel.com,
        linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
        rrangel@chromium.org, upstream@semihalf.com, wsa@kernel.org,
        dabros@google.com
References: <20220916131854.687371-3-jsd@semihalf.com>
 <20230317191834.186690-1-markhas@chromium.org>
From:   Mario Limonciello <mario.limonciello@amd.com>
In-Reply-To: <20230317191834.186690-1-markhas@chromium.org>
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On 3/17/23 14:18, Mark Hasemeyer wrote:
> -	/* Status field in command-response buffer is updated by PSP */
> -	status = READ_ONCE(req->hdr.status);
> +	if (req) {
> +		/* Status field in command-response buffer is updated by PSP */
> +		status = READ_ONCE(req->hdr.status);
> +	} else {
> +		status = psp_smn_read(PSP_MBOX_CMD_OFFSET, &status);
> +		status &= ~PSP_MBOX_FIELDS_READY;
> +	}
>
> The value of the mbox cmd register is getting clobbered by the return value
> from psp_smn_read. This can cause bus arbitration to fail as the driver will
> think it can grab the bus when it's actually in use by the PSP.

Mark - FYI this approach is being superseded by another patch series 
that instead uses MMIO from the CCP driver.

It would be better to comment on that series.

https://lore.kernel.org/linux-i2c/20230310211954.2490-9-mario.limonciello@amd.com/