[PATCH] misc: pci_endpoint_test: Use memcpy_toio()/memcpy_fromio() for BAR tests

Niklas Cassel
2024-03-18T19:31:07Z

The current code uses writel()/readl(), which has an implicit memory
barrier for every single readl()/writel().

Additionally, reading 4 bytes at a time over the PCI bus is not really
optimal, considering that this code is running in an ioctl handler.

Use memcpy_toio()/memcpy_fromio() for BAR tests.

Before patch with a 4MB BAR:
$ time /usr/bin/pcitest -b 1
BAR1: OKAY
real 0m 1.56s

After patch with a 4MB BAR:
$ time /usr/bin/pcitest -b 1
BAR1: OKAY
real 0m 0.54s

Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
drivers/misc/pci_endpoint_test.c | 52 ++++++++++++++++++++++++--------
1 file changed, 40 insertions(+), 12 deletions(-)

diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
index 705029ad8eb5..cb6c9ccf3a5f 100644
--- a/drivers/misc/pci_endpoint_test.c
+++ b/drivers/misc/pci_endpoint_test.c
@@ -272,31 +272,59 @@ static const u32 bar_test_pattern[] = {
0xA5A5A5A5,
};

+static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
+ enum pci_barno barno, int offset,
+ void *write_buf, void *read_buf,
+ int size)
+{
+ memset(write_buf, bar_test_pattern[barno], size);
+ memcpy_toio(test->bar[barno] + offset, write_buf, size);
+
+ /* Make sure that reads are performed after writes. */
+ mb();
+ memcpy_fromio(read_buf, test->bar[barno] + offset, size);
+
+ return memcmp(write_buf, read_buf, size);
+}
+
static bool pci_endpoint_test_bar(struct pci_endpoint_test *test,
enum pci_barno barno)
{
- int j;
- u32 val;
- int size;
+ int j, bar_size, buf_size, iters, remain;
+ void *write_buf;
+ void *read_buf;
struct pci_dev *pdev = test->pdev;
+ struct device *dev = &pdev->dev;

if (!test->bar[barno])
return false;

- size = pci_resource_len(pdev, barno);
+ bar_size = pci_resource_len(pdev, barno);

if (barno == test->test_reg_bar)
- size = 0x4;
+ bar_size = 0x4;

- for (j = 0; j < size; j += 4)
- pci_endpoint_test_bar_writel(test, barno, j,
- bar_test_pattern[barno]);
+ buf_size = min(SZ_1M, bar_size);

- for (j = 0; j < size; j += 4) {
- val = pci_endpoint_test_bar_readl(test, barno, j);
- if (val != bar_test_pattern[barno])
+ write_buf = kmalloc(buf_size, GFP_KERNEL);
+ if (!write_buf)
+ return false;
+
+ read_buf = kmalloc(buf_size, GFP_KERNEL);
+ if (!read_buf)
+ return false;
+
+ iters = bar_size / buf_size;
+ for (j = 0; j < iters; j++)
+ if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j,
+ write_buf, read_buf, buf_size))
+ return false;
+
+ remain = bar_size % buf_size;
+ if (remain)
+ if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * iters,
+ write_buf, read_buf, remain))
return false;
- }

return true;
}
--
2.44.0