From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
To: Dave Jiang <dave.jiang@intel.com>
Cc: <linux-cxl@vger.kernel.org>, <alison.schofield@intel.com>,
<vishal.l.verma@intel.com>, <ira.weiny@intel.com>,
<bwidawsk@kernel.org>, <dan.j.williams@intel.com>
Subject: Re: [PATCH] cxl: check decoder count for end device
Date: Tue, 11 Oct 2022 17:45:34 +0100 [thread overview]
Message-ID: <20221011174534.000072bb@huawei.com> (raw)
In-Reply-To: <166326546707.3348078.8667496731861557941.stgit@djiang5-desk3.ch.intel.com>
On Thu, 15 Sep 2022 11:11:07 -0700
Dave Jiang <dave.jiang@intel.com> wrote:
> CXL spec rev3.0 8.2.4.19.1 added definition for up to 32 decoders. It also
> indicates that for devices, only 10 decoders should be advertised. Add
> check on number of decoders greater than 10 for devices and reset to 10 to
> force spec compliance.
>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Hi Dave
Seems reasonable. I'm a bit curious to whether there is an actual problem if
a device is spec non compliant and advertises more decoders?
Either way does no harm and might let us know something fishy is happening.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
> drivers/cxl/core/hdm.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index d1d2caea5c62..1919d99d157e 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -71,9 +71,23 @@ EXPORT_SYMBOL_NS_GPL(devm_cxl_add_passthrough_decoder, CXL);
> static void parse_hdm_decoder_caps(struct cxl_hdm *cxlhdm)
> {
> u32 hdm_cap;
> + int decoder_count;
> + struct device *dev = &cxlhdm->port->dev;
>
> hdm_cap = readl(cxlhdm->regs.hdm_decoder + CXL_HDM_DECODER_CAP_OFFSET);
> - cxlhdm->decoder_count = cxl_hdm_decoder_count(hdm_cap);
> + decoder_count = cxl_hdm_decoder_count(hdm_cap);
> + /*
> + * CXL spec rev3.0 8.2.4.19.1 indicates CXL devices shall not advertise
> + * more than 10 decoders. Switches and Host Bridges may advertise up to
> + * 32 decoders. Set the decoders to 10 for devices if more than 10 are
> + * found.
> + */
> + if (is_cxl_endpoint(cxlhdm->port) && decoder_count > 10) {
> + dev_warn(dev, "Reset decoders count (%d) to 10, spec violation!\n",
> + decoder_count);
> + decoder_count = 10;
> + }
> + cxlhdm->decoder_count = decoder_count;
> cxlhdm->target_count =
> FIELD_GET(CXL_HDM_DECODER_TARGET_COUNT_MASK, hdm_cap);
> if (FIELD_GET(CXL_HDM_DECODER_INTERLEAVE_11_8, hdm_cap))
>
>
next prev parent reply other threads:[~2022-10-11 16:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-15 18:11 [PATCH] cxl: check decoder count for end device Dave Jiang
2022-10-11 16:45 ` Jonathan Cameron [this message]
2022-10-11 16:56 ` Dave Jiang
2022-10-21 21:17 ` Dan Williams
2022-10-21 21:24 ` Dave Jiang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20221011174534.000072bb@huawei.com \
--to=jonathan.cameron@huawei.com \
--cc=alison.schofield@intel.com \
--cc=bwidawsk@kernel.org \
--cc=dan.j.williams@intel.com \
--cc=dave.jiang@intel.com \
--cc=ira.weiny@intel.com \
--cc=linux-cxl@vger.kernel.org \
--cc=vishal.l.verma@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).