From: Dave Jiang <dave.jiang@intel.com>
To: Jonathan Cameron <Jonathan.Cameron@huawei.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 09:56:30 -0700 [thread overview]
Message-ID: <c6b8121d-1936-acca-157a-d3d21f0b00fc@intel.com> (raw)
In-Reply-To: <20221011174534.000072bb@huawei.com>
On 10/11/2022 9:45 AM, Jonathan Cameron wrote:
> 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?
Not that I'm aware of. Just being cautious.
>
> Either way does no harm and might let us know something fishy is happening.
>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Thanks!
>
>> ---
>> 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 16:59 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
2022-10-11 16:56 ` Dave Jiang [this message]
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=c6b8121d-1936-acca-157a-d3d21f0b00fc@intel.com \
--to=dave.jiang@intel.com \
--cc=Jonathan.Cameron@huawei.com \
--cc=alison.schofield@intel.com \
--cc=bwidawsk@kernel.org \
--cc=dan.j.williams@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).