Date:   Mon, 20 Feb 2023 14:31:12 +0000
From:   Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To:     <alison.schofield@intel.com>
CC:     Dan Williams <dan.j.williams@intel.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Ben Widawsky <bwidawsk@kernel.org>,
        <linux-cxl@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] cxl/hdm: dev_warn() on unsupported mixed mode decoder
Message-ID: <20230220143112.00005678@Huawei.com>
In-Reply-To: <20230218013834.31237-1-alison.schofield@intel.com>
References: <20230218013834.31237-1-alison.schofield@intel.com>
Organization: Huawei Technologies Research and Development (UK) Ltd.
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On Fri, 17 Feb 2023 17:38:34 -0800
alison.schofield@intel.com wrote:

> From: Alison Schofield <alison.schofield@intel.com>
> 
> A mixed mode decoder is programmed with device physical addresses
> that span both ram and pmem partitions of a memdev.
> 
> Linux does not support mixed mode decoders. The driver rejects
> sysfs writes that try to set decoder mode to mixed, and if a
> resource bieng allocated is not wholly contained in either the
> pmem or ram partition of a memdev, it is also rejected. Basically,
> the CXL region driver is not going to create regions with mixed
> mode decoders, but the BIOS could.
> 
> If the kernel driver sees the mixed mode decoder, it will fail to
> enable the region, and emit a dev_dbg() message.
> 
> A dev_dbg() is not noisy enough in this case. Change the message
> to be a dev_warn() that explicitly says mixed mode is not supported.
> 
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Makes sense.
FWIW
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  drivers/cxl/core/hdm.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 45deda18ed32..9eaf93c8ebb0 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -294,8 +294,8 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
>  	else if (resource_contains(&cxlds->ram_res, res))
>  		cxled->mode = CXL_DECODER_RAM;
>  	else {
> -		dev_dbg(dev, "decoder%d.%d: %pr mixed\n", port->id,
> -			cxled->cxld.id, cxled->dpa_res);
> +		dev_warn(dev, "decoder%d.%d: %pr mixed mode not supported\n",
> +			 port->id, cxled->cxld.id, cxled->dpa_res);
>  		cxled->mode = CXL_DECODER_MIXED;
>  	}
>  
> 
> base-commit: a5fcd228ca1db9810ba1ed461c90b6ee933b9daf