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usb: xhci: limit number of ports to 127

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The xHCI driver allocates various port-related structures based on the
maximum number of ports reported by the controller. The Number of Ports
(MaxPorts) field occupies bits 31:24 of the HCSPARAMS1 register and can
represent values up to 255. However, the 'HCS_MAX_PORTS()' macro currently
reads bits 30:24, effectively limiting the maximum to 127.

Fixing the macro increases the reported port limit to 255, which in turn
increases memory usage regardless of how many ports are actually used.

To maintain compatibility and control memory consumption, set
'xhci->max_ports' to the minimum of the value read from 'HCS_MAX_PORTS()'
and 127 (MAX_HC_PORTS). This preserves the existing limit while making
the restriction explicit and easier to adjust in the future.

Summary:
 * Port allocations are now limited to 127.
 * HC max ports macro now correctly reads the MaxPorts value.
 * Macro 'MAX_HC_PORTS' can be modified to set the port limit.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://patch.msgid.link/20251119142417.2820519-17-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Niklas Neronin
2025-11-19 16:24:10 +02:00
committed by Greg Kroah-Hartman
parent df08973556
commit 1668263a13
3 changed files with 7 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/usb/host/xhci-caps.h
View File

@@ -12,8 +12,8 @@
#define HCS_SLOTS_MASK 0xff
/* bits 8:18, Max Interrupters */
#define HCS_MAX_INTRS(p) (((p) >> 8) & 0x7ff)
/* bits 24:31, Max Ports - max value is 0x7F = 127 ports */
#define HCS_MAX_PORTS(p) (((p) >> 24) & 0x7f)
/* bits 31:24, Max Ports - max value is 255 */
#define HCS_MAX_PORTS(p) (((p) >> 24) & 0xff)
/* HCSPARAMS2 - hcs_params2 - bitmasks */
/* bits 0:3, frames or uframes that SW needs to queue transactions

2
drivers/usb/host/xhci.c
View File

@@ -5448,7 +5448,7 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
xhci->hcc_params2 = readl(&xhci->cap_regs->hcc_params2);
xhci->max_slots = HCS_MAX_SLOTS(hcs_params1);
xhci->max_ports = HCS_MAX_PORTS(hcs_params1);
xhci->max_ports = min(HCS_MAX_PORTS(hcs_params1), MAX_HC_PORTS);
/* xhci-plat or xhci-pci might have set max_interrupters already */
if ((!xhci->max_interrupters) || xhci->max_interrupters > HCS_MAX_INTRS(hcs_params1))
xhci->max_interrupters = HCS_MAX_INTRS(hcs_params1);

5
drivers/usb/host/xhci.h
View File

@@ -34,7 +34,10 @@
/* Max number of USB devices for any host controller - limit in section 6.1 */
#define MAX_HC_SLOTS 256
/* Section 5.3.3 - MaxPorts */
/*
* Max Number of Ports. xHCI specification section 5.3.3
* Valid values are in the range of 1 to 255.
*/
#define MAX_HC_PORTS 127
/*