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De Francesco" To: Alison Schofield Cc: Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Vishal Verma , Ira Weiny , Dan Williams , linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] cxl/acpi: Warn on unsupported platform config detection Date: Wed, 26 Jun 2024 12:00:47 +0200 Message-ID: <3636999.dWV9SEqChM@fdefranc-mobl3> In-Reply-To: References: <20240619125949.167936-1-fabio.m.de.francesco@linux.intel.com> Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" On Friday, June 21, 2024 10:57:32=E2=80=AFPM GMT+2 Alison Schofield wrote: > On Wed, Jun 19, 2024 at 02:59:41PM +0200, Fabio M. De Francesco wrote: >=20 Hi Alison, > > Hi Fabio, > You've written such a detailed commit msg, that it pulls me in, > and now I want to understand more.... >=20 > > > Each Host Bridge instance has a corresponding CXL Host Bridge Structure > > (CHBS) ACPI table that identifies its capabilities. CHBS tables can be > > two types: RCRB and CHBCR. >=20 > Is there a spec reference for this? > I'll add a spec reference with v2. > While you're spelling things out, please expand RCRB and CHBCR I'll do it. > > >=20 > > If a Host Bridge is attached to a device that is operating in Restricted > > CXL Device Mode (RCD), BIOS publishes an RCRB with the base address of > > registers that describe its capabilities. > >=20 > > However, the new (CXL 2.0+) Component registers (e.g., Extended Security > > Capability), can only be accessed by means of a base address published > > with a CHBCR. > >=20 > > An algorithm to locate a CHBCR associated with an RCRB would be too > > invasive to land without some concrete motivation. > >=20 > > Therefore, just print a message to inform of unsupported config. > >=20 >=20 > Were users seeing this and confused by this silent failure? > What did it look like before? >=20 Please read Dan on this topic. I think I'll add a few lines to the commit message to summarize Dan's comme= nt. > > > Count how many different CHBS "Version" types are detected by > > cxl_get_chbs_iter(). Then make cxl_get_chbs() print a warning if that s= um > > is greater than 1. > >=20 > > Signed-off-by: Fabio M. De Francesco > > --- > > drivers/cxl/acpi.c | 20 ++++++++++++++------ > > 1 file changed, 14 insertions(+), 6 deletions(-) > >=20 > > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c > > index 571069863c62..9e226a65a5ea 100644 > > --- a/drivers/cxl/acpi.c > > +++ b/drivers/cxl/acpi.c > > @@ -482,6 +482,7 @@ struct cxl_chbs_context { > > unsigned long long uid; > > resource_size_t base; > > u32 cxl_version; > > + int count; >=20 > Maybe s/count/nr_versions to be more explicit of what it counts. > Yes, "nr_versions" is better. Thank you. =46abio > > -- Alison > > }; > > =20 > snip > >=20 >=20