Re: [PATCH v8 8/9] PCI: endpoint: pci-epf-test: Reuse pre-exposed doorbell targets

Hello Koichiro,

On Tue, Feb 17, 2026 at 05:06:00PM +0900, Koichiro Den wrote:
> pci-epf-test advertises the doorbell target to the RC as a BAR number
> and an offset, and the RC rings the doorbell with a single DWORD MMIO
> write.
> 
> Some doorbell backends may report that the doorbell target is already
> exposed via a platform-owned fixed BAR (db_msg[0].bar/offset). In that
> case, reuse the pre-exposed window and do not reprogram the BAR with
> pci_epc_set_bar().
> 
> Also honor db_msg[0].irq_flags when requesting the doorbell IRQ, and
> only restore the original BAR mapping on disable if pci-epf-test
> programmed it.
> 
> Reviewed-by: Frank Li <[email protected]>
> Signed-off-by: Koichiro Den <[email protected]>
> ---

(snip)

> @@ -753,22 +771,33 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
>  	reg->doorbell_data = cpu_to_le32(msg->data);
>  	reg->doorbell_bar = cpu_to_le32(bar);
>  
> -	msg = &epf->db_msg[0].msg;
> -	ret = pci_epf_align_inbound_addr(epf, bar, ((u64)msg->address_hi << 32) | msg->address_lo,
> -					 &epf_test->db_bar.phys_addr, &offset);
> +	if (db->bar == NO_BAR) {
> +		ret = pci_epf_align_inbound_addr(epf, bar,
> +						 ((u64)msg->address_hi << 32) |
> +						 msg->address_lo,
> +						 &epf_test->db_bar.phys_addr,
> +						 &offset);
>  
> -	if (ret)
> -		goto err_free_irq;
> +		if (ret)
> +			goto err_free_irq;
> +	}

I tried this series on Rock5b (RK3588), and was surprised to see the doorbell
test case still failing.


> +
> +	if (size_add(offset, sizeof(u32)) > epf->bar[bar].size)
> +		goto err_doorbell_cleanup;

It turns out that this check is the reason for it still failing.

You see, for a BAR that is marked as BAR_RESERVED, pci-epf-test will not
allocate backing memory, so epf->bar[bar].size will be 0.

If I removed this check, I could get the test case to pass.

As I suggested in my previous email, perhaps this check is better suited
in pci_epf_alloc_doorbell(). (As a DWORD alignment check inside
pci_epf_alloc_doorbell(). pci_epf_alloc_doorbell() could itself return
error if the doorbell is not DWORD aligned.)

That way, you could remove this check from pci_epf_test_enable_doorbell(),
and we don't need to care about epf->bar[bar].size.


Kind regards,
Niklas