Re: [PATCH v4 3/5] PCI: endpoint: pci-epf-test: Add doorbell test support

[Niklas Cassel <cassel@kernel.org>]

On Thu, Oct 31, 2024 at 12:27:02PM -0400, Frank Li wrote:
> Add three registers: doorbell_bar, doorbell_addr, and doorbell_data,
> along with doorbell_done. Use pci_epf_alloc_doorbell() to allocate a
> doorbell address space.
> 
> Enable the Root Complex (RC) side driver to trigger pci-epc-test's doorbell
> callback handler by writing doorbell_data to the mapped doorbell_bar's
> address space.
> 
> Set doorbell_done in the doorbell callback to indicate completion.
> 
> To avoid broken compatibility, add new command COMMAND_ENABLE_DOORBELL
> and COMMAND_DISABLE_DOORBELL. Host side need send COMMAND_ENABLE_DOORBELL
> to map one bar's inbound address to MSI space. the command
> COMMAND_DISABLE_DOORBELL to recovery original inbound address mapping.
> 
> 	 	Host side new driver	Host side old driver
> 
> EP: new driver      S				F
> EP: old driver      F				F
> 
> S: If EP side support MSI, 'pcitest -B' return success.
>    If EP side doesn't support MSI, the same to 'F'.
> 
> F: 'pcitest -B' return failure, other case as usual.
> 
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
> change from v3 to v4
> - remove revid requirement
> - Add command COMMAND_ENABLE_DOORBELL and COMMAND_DISABLE_DOORBELL.
> - call pci_epc_set_bar() to map inbound address to MSI space only at
> COMMAND_ENABLE_DOORBELL.
> ---
>  drivers/pci/endpoint/functions/pci-epf-test.c | 104 ++++++++++++++++++++++++++
>  1 file changed, 104 insertions(+)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 7c2ed6eae53ad..dcb69921497fd 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -11,12 +11,14 @@
>  #include <linux/dmaengine.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
> +#include <linux/msi.h>
>  #include <linux/slab.h>
>  #include <linux/pci_ids.h>
>  #include <linux/random.h>
>  
>  #include <linux/pci-epc.h>
>  #include <linux/pci-epf.h>
> +#include <linux/pci-ep-msi.h>
>  #include <linux/pci_regs.h>
>  
>  #define IRQ_TYPE_INTX			0
> @@ -29,6 +31,8 @@
>  #define COMMAND_READ			BIT(3)
>  #define COMMAND_WRITE			BIT(4)
>  #define COMMAND_COPY			BIT(5)
> +#define COMMAND_ENABLE_DOORBELL		BIT(6)
> +#define COMMAND_DISABLE_DOORBELL	BIT(7)
>  
>  #define STATUS_READ_SUCCESS		BIT(0)
>  #define STATUS_READ_FAIL		BIT(1)
> @@ -39,6 +43,11 @@
>  #define STATUS_IRQ_RAISED		BIT(6)
>  #define STATUS_SRC_ADDR_INVALID		BIT(7)
>  #define STATUS_DST_ADDR_INVALID		BIT(8)
> +#define STATUS_DOORBELL_SUCCESS		BIT(9)
> +#define STATUS_DOORBELL_ENABLE_SUCCESS	BIT(10)
> +#define STATUS_DOORBELL_ENABLE_FAIL	BIT(11)
> +#define STATUS_DOORBELL_DISABLE_SUCCESS BIT(12)
> +#define STATUS_DOORBELL_DISABLE_FAIL	BIT(13)
>  
>  #define FLAG_USE_DMA			BIT(0)
>  
> @@ -74,6 +83,9 @@ struct pci_epf_test_reg {
>  	u32	irq_type;
>  	u32	irq_number;
>  	u32	flags;
> +	u32	doorbell_bar;
> +	u32	doorbell_addr;
> +	u32	doorbell_data;
>  } __packed;
>  
>  static struct pci_epf_header test_header = {
> @@ -630,6 +642,60 @@ 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)
> +{
> +	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;
> +	u32 align;
> +	int ret;
> +
> +	align = epf_test->epc_features->align;
> +	align = align ? align : 128;
> +
> +	if (bar < BAR_0 || bar == epf_test->test_reg_bar || !epf->db_msg) {
> +		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.barno = bar;
> +	db_bar.size = epf->bar[bar].size;
> +	db_bar.flags = epf->bar[bar].flags;
> +	db_bar.addr = NULL;
> +
> +	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &db_bar);
> +	if (!ret)
> +		reg->status |= STATUS_DOORBELL_ENABLE_SUCCESS;
> +}
> +
> +static void pci_epf_disable_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;
> +	int ret;
> +
> +	if (bar < BAR_0 || bar == epf_test->test_reg_bar || !epf->db_msg) {
> +		reg->status |= STATUS_DOORBELL_DISABLE_FAIL;
> +		return;
> +	}
> +
> +	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf->bar[bar]);
> +	if (ret)
> +		reg->status |= STATUS_DOORBELL_DISABLE_FAIL;
> +	else
> +		reg->status |= STATUS_DOORBELL_DISABLE_SUCCESS;
> +}
> +
>  static void pci_epf_test_cmd_handler(struct work_struct *work)
>  {
>  	u32 command;
> @@ -676,6 +742,14 @@ static void pci_epf_test_cmd_handler(struct work_struct *work)
>  		pci_epf_test_copy(epf_test, reg);
>  		pci_epf_test_raise_irq(epf_test, reg);
>  		break;
> +	case COMMAND_ENABLE_DOORBELL:
> +		pci_epf_enable_doorbell(epf_test, reg);
> +		pci_epf_test_raise_irq(epf_test, reg);
> +		break;
> +	case COMMAND_DISABLE_DOORBELL:
> +		pci_epf_disable_doorbell(epf_test, reg);
> +		pci_epf_test_raise_irq(epf_test, reg);
> +		break;
>  	default:
>  		dev_err(dev, "Invalid command 0x%x\n", command);
>  		break;
> @@ -810,11 +884,24 @@ static int pci_epf_test_link_down(struct pci_epf *epf)
>  	return 0;
>  }
>  
> +static int pci_epf_test_doorbell(struct pci_epf *epf, int index)
> +{
> +	struct pci_epf_test *epf_test = epf_get_drvdata(epf);
> +	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
> +	struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
> +
> +	reg->status |= STATUS_DOORBELL_SUCCESS;
> +	pci_epf_test_raise_irq(epf_test, reg);
> +
> +	return 0;
> +}
> +
>  static const struct pci_epc_event_ops pci_epf_test_event_ops = {
>  	.epc_init = pci_epf_test_epc_init,
>  	.epc_deinit = pci_epf_test_epc_deinit,
>  	.link_up = pci_epf_test_link_up,
>  	.link_down = pci_epf_test_link_down,
> +	.doorbell = pci_epf_test_doorbell,
>  };
>  
>  static int pci_epf_test_alloc_space(struct pci_epf *epf)
> @@ -909,6 +996,23 @@ static int pci_epf_test_bind(struct pci_epf *epf)
>  	if (ret)
>  		return ret;
>  
> +	ret = pci_epf_alloc_doorbell(epf, 1);

Calling pci_epf_alloc_doorbell() unconditionally from bind will lead to the
following print for all platforms that have not configured a msi-parent:
[   64.543388] a40000000.pcie-ep: Failed to allocate MSI

In ealier discussions, I thought that you wanted to call
pci_epf_alloc_doorbell() in pci_epf_enable_doorbell(), and then let
pci_epf_enable_doorbell() return STATUS_DOORBELL_ENABLE_FAIL
if pci_epf_enable_doorbell() failed.


Perhaps you could modify pci_epf_enable_doorbell() to also check if
dev->msi.domain is NULL, before calling pci_epc_alloc_doorbell(),
and if dev->msi.domain is NULL, perhaps print a clearer error,
e.g. "no msi domain found, is 'msi-parent' device tree property missing?"
Or put the text in a comment next to the error check, if you think that a
print seems too silly.


> +	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;
> +
> +		align = align ? align : 128;
> +		doorbell_addr = msg->address_hi;
> +		doorbell_addr <<= 32;
> +		doorbell_addr |= msg->address_lo;
> +
> +		reg->doorbell_addr = doorbell_addr & (align - 1);
> +		reg->doorbell_data = msg->data;
> +		reg->doorbell_bar = pci_epc_get_next_free_bar(epc_features, test_reg_bar + 1);
> +	}
> +
>  	return 0;
>  }
>  
> 
> -- 
> 2.34.1
>