USB: pci-quirks: Fix HCCPARAMS register error for LS7A EHCI

commit e71f7f4 upstream.

LS7A EHCI controller doesn't have extended capabilities, so the EECP
(EHCI Extended Capabilities Pointer) field of HCCPARAMS register should
be 0x0, but it reads as 0xa0 now. This is a hardware flaw and will be
fixed in future, now just clear the EECP field to avoid error messages
on boot:

......
[    0.581675] pci 0000:00:04.1: EHCI: unrecognized capability ff
[    0.581699] pci 0000:00:04.1: EHCI: unrecognized capability ff
[    0.581716] pci 0000:00:04.1: EHCI: unrecognized capability ff
[    0.581851] pci 0000:00:04.1: EHCI: unrecognized capability ff
......
[    0.581916] pci 0000:00:05.1: EHCI: unrecognized capability ff
[    0.581951] pci 0000:00:05.1: EHCI: unrecognized capability ff
[    0.582704] pci 0000:00:05.1: EHCI: unrecognized capability ff
[    0.582799] pci 0000:00:05.1: EHCI: unrecognized capability ff
......

Cc: stable <stable@kernel.org>
Signed-off-by: Baoqi Zhang <zhangbaoqi@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Link: https://lore.kernel.org/r/20250202124935.480500-1-chenhuacai@loongson.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: chenhuacai

drivers/usb/host/pci-quirks.c

@@ -958,6 +958,15 @@ static void quirk_usb_disable_ehci(struct pci_dev *pdev)
 	 * booting from USB disk or using a usb keyboard
 	 */
 	hcc_params = readl(base + EHCI_HCC_PARAMS);
+
+	/* LS7A EHCI controller doesn't have extended capabilities, the
+	 * EECP (EHCI Extended Capabilities Pointer) field of HCCPARAMS
+	 * register should be 0x0 but it reads as 0xa0.  So clear it to
+	 * avoid error messages on boot.
+	 */
+	if (pdev->vendor == PCI_VENDOR_ID_LOONGSON && pdev->device == 0x7a14)
+		hcc_params &= ~(0xffL << 8);
+
 	offset = (hcc_params >> 8) & 0xff;
 	while (offset && --count) {
 		pci_read_config_dword(pdev, offset, &cap);