linux-kernel - Re: [PATCH 1/3] cxl: Set target type of root decoder based on CFMWS restrictions

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Message-ID: <20240804172436.00003275@Huawei.com>
Date: Sun, 4 Aug 2024 17:24:36 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Huang Ying <ying.huang@...el.com>
CC: Dan Williams <dan.j.williams@...el.com>, Dave Jiang
	<dave.jiang@...el.com>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Davidlohr Bueso <dave@...olabs.net>, "Alison
 Schofield" <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, "Alejandro
 Lucero" <alucerop@....com>
Subject: Re: [PATCH 1/3] cxl: Set target type of root decoder based on CFMWS
 restrictions

On Mon, 29 Jul 2024 16:46:09 +0800
Huang Ying <ying.huang@...el.com> wrote:

> Now, the target type of root decoder is hard-coded to HOSTONLYMEM,
> because only type3 expanders are supported.  To support type2
> accelerators, set the target type of root decoder based on the
> window restrictions field of CFMWS entry.
> 
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Suggested-by: Dan Williams <dan.j.williams@...el.com>
> Cc: Davidlohr Bueso <dave@...olabs.net>
> Cc: Jonathan Cameron <jonathan.cameron@...wei.com>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: Alison Schofield <alison.schofield@...el.com>
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: Alejandro Lucero <alucerop@....com>
> ---
>  drivers/cxl/acpi.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 82b78e331d8e..40c92ad29122 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -382,7 +382,10 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
>  
>  	cxld = &cxlrd->cxlsd.cxld;
>  	cxld->flags = cfmws_to_decoder_flags(cfmws->restrictions);
> -	cxld->target_type = CXL_DECODER_HOSTONLYMEM;
> +	if (cxld->flags & CXL_DECODER_F_TYPE2)

These flags need updating or we are going to run into problems
long term.

As of more recent specs, the distinction is messier than it was and
it's device coherent HDM-D / HDM-DB (second one being type2 or type3 with
BI support) and/or Host only coherent HDM-H.

I'm curious on whether anyone is support both on same CFWMS?
I believe it is possible and the spec doesn't rule it out.

Jonathan


> +		cxld->target_type = CXL_DECODER_DEVMEM;
> +	else
> +		cxld->target_type = CXL_DECODER_HOSTONLYMEM;
>  	cxld->hpa_range = (struct range) {
>  		.start = cfmws->base_hpa,
>  		.end = cfmws->base_hpa + cfmws->window_size - 1,