linux-kernel - Re: [PATCH 2/3] misc: pci_endpoint

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Message-ID: <20230902051155.GC2913@thinkpad>
Date:   Sat, 2 Sep 2023 10:41:55 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Frank Li <Frank.Li@....com>
Cc:     tglx@...utronix.de, aisheng.dong@....com, bhelgaas@...gle.com,
        devicetree@...r.kernel.org, festevam@...il.com,
        imx@...ts.linux.dev, jdmason@...zu.us, kernel@...gutronix.de,
        kishon@...com, krzysztof.kozlowski+dt@...aro.org, kw@...ux.com,
        linux-arm-kernel@...ts.infradead.org, linux-imx@....com,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        lorenzo.pieralisi@....com, lpieralisi@...nel.org, maz@...nel.org,
        ntb@...ts.linux.dev, peng.fan@....com, robh+dt@...nel.org,
        s.hauer@...gutronix.de, shawnguo@...nel.org
Subject: Re: [PATCH 2/3] misc: pci_endpoint_test: Add doorbell test case

On Wed, Apr 26, 2023 at 04:34:35PM -0400, Frank Li wrote:
> Reused flags as capability register in pci_endpoint_test struct to
> support older driver versions. Save capability flags to 'cap' field
> of struct pci_endpoint_test to prevent reading non-existent address.
> 

This won't work, please see below.

> Add three registers: PCIE_ENDPOINT_TEST_DB_BAR, PCIE_ENDPOINT_TEST_DB_ADDR,
> PCIE_ENDPOINT_TEST_DB_DATA.
> 
> Write data from PCI_ENDPOINT_TEST_DB_DATA to address from
> PCI_ENDPOINT_TEST_DB_ADDR to trigger doorbell and wait for remote
> endpoint feedback.

"wait for endpoint response"

> 
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
>  drivers/misc/pci_endpoint_test.c | 41 ++++++++++++++++++++++++++++++++
>  include/uapi/linux/pcitest.h     |  1 +
>  2 files changed, 42 insertions(+)
> 
> diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
> index ed4d0ef5e5c3..3320a3334594 100644
> --- a/drivers/misc/pci_endpoint_test.c
> +++ b/drivers/misc/pci_endpoint_test.c
> @@ -52,6 +52,7 @@
>  #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 PCI_ENDPOINT_TEST_LOWER_SRC_ADDR	0x0c
>  #define PCI_ENDPOINT_TEST_UPPER_SRC_ADDR	0x10
> @@ -66,7 +67,12 @@
>  #define PCI_ENDPOINT_TEST_IRQ_NUMBER		0x28
>  
>  #define PCI_ENDPOINT_TEST_FLAGS			0x2c
> +#define PCI_ENDPOINT_TEST_DB_BAR		0x30
> +#define PCI_ENDPOINT_TEST_DB_ADDR		0x34
> +#define PCI_ENDPOINT_TEST_DB_DATA		0x38
> +
>  #define FLAG_USE_DMA				BIT(0)
> +#define FLAG_SUPPORT_DOORBELL			BIT(1)
>  
>  #define PCI_DEVICE_ID_TI_AM654			0xb00c
>  #define PCI_DEVICE_ID_TI_J7200			0xb00f
> @@ -102,6 +108,7 @@ enum pci_barno {
>  	BAR_3,
>  	BAR_4,
>  	BAR_5,
> +	NO_BAR = -1,
>  };
>  
>  struct pci_endpoint_test {
> @@ -118,6 +125,7 @@ struct pci_endpoint_test {
>  	enum pci_barno test_reg_bar;
>  	size_t alignment;
>  	const char *name;
> +	u32 cap;
>  };
>  
>  struct pci_endpoint_test_data {
> @@ -713,6 +721,35 @@ static bool pci_endpoint_test_set_irq(struct pci_endpoint_test *test,
>  	return false;
>  }
>  
> +static bool pci_endpoint_test_doorbell(struct pci_endpoint_test *test)
> +{
> +	enum pci_barno bar;
> +	u32 data;
> +	u32 addr;
> +
> +	if (!(test->cap & FLAG_SUPPORT_DOORBELL))
> +		return false;
> +
> +	bar = pci_endpoint_test_readl(test, PCI_ENDPOINT_TEST_DB_BAR);
> +	if (bar == NO_BAR)
> +		return false;

Is this possible?

> +
> +	data = pci_endpoint_test_readl(test, PCI_ENDPOINT_TEST_DB_DATA);
> +	addr = pci_endpoint_test_readl(test, PCI_ENDPOINT_TEST_DB_ADDR);
> +	bar = pci_endpoint_test_readl(test, PCI_ENDPOINT_TEST_DB_BAR);
> +
> +	pci_endpoint_test_writel(test, PCI_ENDPOINT_TEST_STATUS, 0);
> +	pci_endpoint_test_bar_writel(test, bar, addr, data);

>From patch 1, I understood that EP supports multiple doorbell. But you are not
making use of it here?

> +
> +	wait_for_completion(&test->irq_raised);
> +

No timeout?

> +	data = pci_endpoint_test_readl(test, PCI_ENDPOINT_TEST_STATUS);
> +	if (data & STATUS_DOORBELL_SUCCESS)

Please use a separate variable.

> +		return true;
> +
> +	return false;
> +}
> +
>  static long pci_endpoint_test_ioctl(struct file *file, unsigned int cmd,
>  				    unsigned long arg)
>  {
> @@ -760,6 +797,9 @@ static long pci_endpoint_test_ioctl(struct file *file, unsigned int cmd,
>  	case PCITEST_CLEAR_IRQ:
>  		ret = pci_endpoint_test_clear_irq(test);
>  		break;
> +	case PCITEST_DOORBELL:
> +		ret = pci_endpoint_test_doorbell(test);
> +		break;
>  	}
>  
>  ret:
> @@ -887,6 +927,7 @@ static int pci_endpoint_test_probe(struct pci_dev *pdev,
>  	misc_device->parent = &pdev->dev;
>  	misc_device->fops = &pci_endpoint_test_fops;
>  
> +	test->cap = pci_endpoint_test_readl(test, PCI_ENDPOINT_TEST_FLAGS);

This register will be overwritten by this driver during (copy,read,write) tests.
So this logic will not work.

- Mani

>  	err = misc_register(misc_device);
>  	if (err) {
>  		dev_err(dev, "Failed to register device\n");
> diff --git a/include/uapi/linux/pcitest.h b/include/uapi/linux/pcitest.h
> index f9c1af8d141b..479ca1aa3ae0 100644
> --- a/include/uapi/linux/pcitest.h
> +++ b/include/uapi/linux/pcitest.h
> @@ -20,6 +20,7 @@
>  #define PCITEST_SET_IRQTYPE	_IOW('P', 0x8, int)
>  #define PCITEST_GET_IRQTYPE	_IO('P', 0x9)
>  #define PCITEST_CLEAR_IRQ	_IO('P', 0x10)
> +#define PCITEST_DOORBELL	_IO('P', 0x11)
>  
>  #define PCITEST_FLAGS_USE_DMA	0x00000001
>  
> -- 
> 2.34.1
> 

-- 
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