* Re: [PATCH v1 1/2] cxl_test: enable zero sized decoders under hb0
[not found] <aYynWqJ7u-v-6WsZ@gourry-fedora-PF4VCD3F>
@ 2026-05-08 4:00 ` Richard Cheng
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From: Richard Cheng @ 2026-05-08 4:00 UTC (permalink / raw)
To: gourry, Vishal Aslot
Cc: alison.schofield, dan.j.williams, dave.jiang, dave, ira.weiny,
jonathan.cameron, linux-cxl, linux-kernel, ming.li, peterz,
vishal.l.verma, newtonl, kristinc, kaihengf, kobak,
Jonathan Cameron, Richard Cheng
On Tue, Oct 14, 2025 at 07:40:05PM -0700, Vishal Aslot wrote:
> The cxl core in linux updated to supported committed
> decoders of zero size, because this is allowed by
> the CXL spec.
>
> This patch updates cxl_test to enable decoders 1 and 2
> in the host-bridge 0 port, in a switch uport under hb0,
> and the endpoints ports with size zero simulating
> committed zero sized decoders.
Hi Vishal,
Thanks for the patch series, it resolve the issue I hit
from my end.
> + cxled->state = CXL_DECODER_STATE_AUTO;
IMHO, CXL_DECODER_STATE_AUTO suggests the kernel auto-discovered and is
willing to auto-tear-down. For a locked BIOS-committed slot that is
explicitly not under kernel control, STATE_MANUAL seems closer to
the intent, or, if locked decoders need their own tracking.
Maybe worth at least a comment justifying AUTO here.
> +static void size_zero_mock_decoder_ep(struct cxl_decoder *cxld, u64 base)
> +{
> + struct cxl_endpoint_decoder *cxled;
> +
> + cxled = to_cxl_endpoint_decoder(&cxld->dev);
> + cxld->hpa_range = (struct range){
> + .start = base,
> + .end = base - 1, /* Size 0 */
> + };
> +
Maybe something like the following to utilize DEFINE_RANGE() macro ?
"""
cxld->hpa_range = DEFINE_RANGE(base, base - 1);
"""
What do you think ?
> + cxld->interleave_ways = 2;
> + cxld->interleave_granularity = 4096;
> + cxld->target_type = CXL_DECODER_HOSTONLYMEM;
> + cxld->flags = CXL_DECODER_F_ENABLE;
> + cxled->state = CXL_DECODER_STATE_AUTO;
> + cxld->commit = mock_decoder_commit;
> + cxld->reset = mock_decoder_reset;
> +}
> +
> +static void size_zero_mock_decoder_sw(struct device *dev, u64 base, int i)
> +{
> + struct cxl_switch_decoder *cxlsd;
> + struct cxl_decoder *cxld;
> +
> + cxlsd = to_cxl_switch_decoder(dev);
> + cxld = &cxlsd->cxld;
> + cxld->flags = CXL_DECODER_F_ENABLE;
> + cxld->target_type = CXL_DECODER_HOSTONLYMEM;
> + if (i == 0)
> + cxld->interleave_ways = 2;
> + else
> + cxld->interleave_ways = 1;
> + cxld->interleave_granularity = 4096;
> + cxld->hpa_range = (struct range) {
> + .start = base,
> + .end = base - 1, /* Size 0 */
> + };
Ditto for DEFINE_RANGE() macro.
> +}
> +
Best regards,
Richard Cheng.
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