linux-kernel - Re: [PATCH v5 3/5] PCI: endpoint: pci-epf-test: Add doorbell test support

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Message-ID: <ZzMtKUFi30_o6SwL@ryzen>
Date: Tue, 12 Nov 2024 11:25:45 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Frank Li <Frank.Li@....com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	imx@...ts.linux.dev, dlemoal@...nel.org, maz@...nel.org,
	tglx@...utronix.de, jdmason@...zu.us
Subject: Re: [PATCH v5 3/5] PCI: endpoint: pci-epf-test: Add doorbell test
 support

On Mon, Nov 11, 2024 at 03:43:12PM +0100, Niklas Cassel wrote:
> On Fri, Nov 08, 2024 at 02:43:30PM -0500, Frank Li wrote:
> 
> Perhaps create a helper function so that you don't need to duplicate it.

Something like this on top of your series:

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 8ede7aded03ee..b1707b4425432 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -656,16 +656,25 @@ static void pci_epf_test_raise_irq(struct pci_epf_test *epf_test,
 	}
 }
 
-static void pci_epf_enable_doorbell(struct pci_epf_test *epf_test, struct pci_epf_test_reg *reg)
+static int pci_epf_get_doorbell_addr(struct pci_epf_test *epf_test,
+				     enum pci_barno bar, u64 *db_base,
+				     u64 *db_offset)
 {
-	enum pci_barno bar = reg->doorbell_bar;
 	struct pci_epf *epf = epf_test->epf;
-	struct pci_epc *epc = epf->epc;
-	struct pci_epf_bar db_bar;
 	struct msi_msg *msg;
-	u64 doorbell_addr;
+	u64 doorbell_addr, mask;
 	u32 align;
-	int ret;
+
+	if (bar < BAR_0 || bar == epf_test->test_reg_bar || !epf->db_msg)
+		return -EINVAL;
+
+	msg = &epf->db_msg[0].msg;
+	doorbell_addr = msg->address_hi;
+	doorbell_addr <<= 32;
+	doorbell_addr |= msg->address_lo;
+
+	if (!doorbell_addr)
+		return -EINVAL;
 
 	align = epf_test->epc_features->align;
 	align = align ? align : 128;
@@ -673,17 +682,28 @@ static void pci_epf_enable_doorbell(struct pci_epf_test *epf_test, struct pci_ep
 	if (epf_test->epc_features->bar[bar].type == BAR_FIXED)
 		align = max(epf_test->epc_features->bar[bar].fixed_size, align);
 
-	if (bar < BAR_0 || bar == epf_test->test_reg_bar || !epf->db_msg) {
+	mask = align - 1;
+	*db_base = doorbell_addr & ~mask;
+	*db_offset = doorbell_addr & mask;
+
+	return 0;
+}
+
+static void pci_epf_enable_doorbell(struct pci_epf_test *epf_test, struct pci_epf_test_reg *reg)
+{
+	enum pci_barno bar = reg->doorbell_bar;
+	struct pci_epf *epf = epf_test->epf;
+	struct pci_epc *epc = epf->epc;
+	struct pci_epf_bar db_bar;
+	u64 db_base, db_offset;
+	int ret;
+
+	if (pci_epf_get_doorbell_addr(epf_test, bar, &db_base, &db_offset)) {
 		reg->status |= STATUS_DOORBELL_ENABLE_FAIL;
 		return;
 	}
 
-	msg = &epf->db_msg[0].msg;
-	doorbell_addr = msg->address_hi;
-	doorbell_addr <<= 32;
-	doorbell_addr |= msg->address_lo;
-
-	db_bar.phys_addr = round_down(doorbell_addr, align);
+	db_bar.phys_addr = db_base;
 	db_bar.barno = bar;
 	db_bar.size = epf->bar[bar].size;
 	db_bar.flags = epf->bar[bar].flags;
@@ -1015,9 +1035,7 @@ static int pci_epf_test_bind(struct pci_epf *epf)
 	ret = pci_epf_alloc_doorbell(epf, 1);
 	if (!ret) {
 		struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
-		struct msi_msg *msg = &epf->db_msg[0].msg;
-		u32 align = epc_features->align;
-		u64 doorbell_addr;
+		u64 db_base, db_offset;
 		enum pci_barno bar;
 
 		bar = pci_epc_get_next_free_bar(epc_features, test_reg_bar + 1);
@@ -1031,17 +1049,15 @@ static int pci_epf_test_bind(struct pci_epf *epf)
 			return 0;
 		}
 
-		align = align ? align : 128;
-
-		if (epf_test->epc_features->bar[bar].type == BAR_FIXED)
-			align = max(epf_test->epc_features->bar[bar].fixed_size, align);
-
-		doorbell_addr = msg->address_hi;
-		doorbell_addr <<= 32;
-		doorbell_addr |= msg->address_lo;
+		if (pci_epf_get_doorbell_addr(epf_test, bar, &db_base,
+					      &db_offset)) {
+			dev_err(&epf->dev, "Failed to get doorbell address\n");
+			free_irq(epf->db_msg[0].virq, epf_test);
+			return 0;
+		}
 
-		reg->doorbell_addr = doorbell_addr & (align - 1);
-		reg->doorbell_data = msg->data;
+		reg->doorbell_addr = db_offset;
+		reg->doorbell_data = epf->db_msg[0].msg.data;
 		reg->doorbell_bar = bar;
 	}
 



> 
> Also one function is doing:
> reg->doorbell_addr = doorbell_addr & (align - 1);
> 
> to align, the other one is doing:
> round_down(doorbell_addr, align);
> 
> Which seems to be a bit inconsistent.

I now see why you did this.
One function is using the db offset, and the other is using the db base.

I strongly suggest that you rename:
reg->doorbell_addr to reg->doorbell_offset
and
PCI_ENDPOINT_TEST_DB_ADDR to PCI_ENDPOINT_TEST_DB_OFFSET

since the current names are very confusing.


Kind regards,
Niklas