From: Niklas Neronin <niklas.neronin@linux.intel.com>
To: mathias.nyman@linux.intel.com
Cc: linux-usb@vger.kernel.org, michal.pecio@gmail.com,
Niklas Neronin <niklas.neronin@linux.intel.com>
Subject: [PATCH v2 03/13] usb: xhci: use cached HCSPARAMS1 value
Date: Thu, 13 Nov 2025 13:56:30 +0100 [thread overview]
Message-ID: <20251113125640.2875608-4-niklas.neronin@linux.intel.com> (raw)
In-Reply-To: <20251113125640.2875608-1-niklas.neronin@linux.intel.com>
The Structural Parameters 1 (HCSPARAMS1) register is read and cached in
'xhci->hcs_params1' during host controller initialization. Since this
register is read-only and its value remains constant for the lifetime of
the controller, re-reading it later is unnecessary.
Replace subsequent register reads with the cached 'xhci->hcs_params1'
value to avoid redundant MMIO access.
Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
---
drivers/usb/host/xhci.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 42975df517cb..0630269e5ab7 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4222,8 +4222,7 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
xhci_err(xhci, "Error while assigning device slot ID: %s\n",
xhci_trb_comp_code_string(command->status));
xhci_err(xhci, "Max number of devices this xHCI host supports is %u.\n",
- HCS_MAX_SLOTS(
- readl(&xhci->cap_regs->hcs_params1)));
+ HCS_MAX_SLOTS(xhci->hcs_params1));
xhci_free_command(xhci, command);
return 0;
}
--
2.50.1
next prev parent reply other threads:[~2025-11-13 12:58 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-13 12:56 [PATCH v2 00/13] usb: xhci: Host Controller Capability Registers rework Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 01/13] usb: xhci: remove deprecated TODO comment Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 02/13] usb: xhci: remove unused trace operation and argument Niklas Neronin
2025-11-13 12:56 ` Niklas Neronin [this message]
2025-11-13 12:56 ` [PATCH v2 04/13] usb: xhci: simplify handling of Structural Parameters 1 values Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 05/13] usb: xhci: limit number of ports to 127 Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 06/13] usb: xhci: limit number of interrupts to 128 Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 07/13] usb: xhci: improve xhci-caps.h comments Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 08/13] usb: xhci: simplify Isochronous Scheduling Threshold handling Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 09/13] usb: xhci: simplify Max Scratchpad buffer macros Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 10/13] usb: xhci: drop xhci-caps.h dependence on xhci-ext-caps.h Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 11/13] usb: xhci: standardize single bit-field macros Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 12/13] usb: xhci: standardize multi " Niklas Neronin
2025-11-13 12:56 ` [PATCH v2 13/13] usb: xhci: use 64-bit Addressing Capability macro Niklas Neronin
2025-11-19 14:00 ` [PATCH v2 00/13] usb: xhci: Host Controller Capability Registers rework Mathias Nyman
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