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From: Mathias Nyman <mathias.nyman@linux.intel.com>
To: <gregkh@linuxfoundation.org>
Cc: <linux-usb@vger.kernel.org>,
	Niklas Neronin <niklas.neronin@linux.intel.com>,
	Mathias Nyman <mathias.nyman@linux.intel.com>
Subject: [PATCH 14/23] usb: xhci: use cached HCSPARAMS1 value
Date: Wed, 19 Nov 2025 16:24:08 +0200	[thread overview]
Message-ID: <20251119142417.2820519-15-mathias.nyman@linux.intel.com> (raw)
In-Reply-To: <20251119142417.2820519-1-mathias.nyman@linux.intel.com>

From: Niklas Neronin <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>
Signed-off-by: Mathias Nyman <mathias.nyman@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 7ac8198d0d7b..dbe64ea47936 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4235,8 +4235,7 @@ 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;
 	}
-- 
2.43.0


  parent reply	other threads:[~2025-11-19 14:24 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-19 14:23 [PATCH 00/23] xhci features for usb-next Mathias Nyman
2025-11-19 14:23 ` [PATCH 01/23] usb: xhci: limit run_graceperiod for only usb 3.0 devices Mathias Nyman
2025-11-19 14:23 ` [PATCH 02/23] xhci: Add helper to find trb from its dma address Mathias Nyman
2025-11-19 14:23 ` [PATCH 03/23] xhci: simplify and rework trb_in_td() Mathias Nyman
2025-11-19 14:23 ` [PATCH 04/23] usb: xhci: rework xhci_decode_portsc() Mathias Nyman
2025-11-19 14:23 ` [PATCH 05/23] usb: xhci: add tracing for PORTSC register writes Mathias Nyman
2025-11-19 14:24 ` [PATCH 06/23] usb: xhci: add helper to read PORTSC register Mathias Nyman
2025-11-19 14:24 ` [PATCH 07/23] usb: xhci: add USB Port Register Set struct Mathias Nyman
2025-11-19 14:24 ` [PATCH 08/23] usb: xhci: implement " Mathias Nyman
2025-11-19 14:24 ` [PATCH 09/23] usb: xhci: Assume that endpoints halt as specified Mathias Nyman
2025-11-19 14:24 ` [PATCH 10/23] usb: xhci: Don't unchain link TRBs on quirky HCs Mathias Nyman
2025-11-19 14:24 ` [PATCH 11/23] usb: xhci: replace use of system_wq with system_percpu_wq Mathias Nyman
2025-11-19 14:24 ` [PATCH 12/23] usb: xhci: remove deprecated TODO comment Mathias Nyman
2025-11-19 14:24 ` [PATCH 13/23] usb: xhci: remove unused trace operation and argument Mathias Nyman
2025-11-19 14:24 ` Mathias Nyman [this message]
2025-11-19 14:24 ` [PATCH 15/23] usb: xhci: simplify handling of Structural Parameters 1 values Mathias Nyman
2025-11-19 14:24 ` [PATCH 16/23] usb: xhci: limit number of ports to 127 Mathias Nyman
2025-11-19 14:24 ` [PATCH 17/23] usb: xhci: limit number of interrupts to 128 Mathias Nyman
2025-11-19 14:24 ` [PATCH 18/23] usb: xhci: improve xhci-caps.h comments Mathias Nyman
2025-11-19 14:24 ` [PATCH 19/23] usb: xhci: simplify Isochronous Scheduling Threshold handling Mathias Nyman
2025-11-19 14:24 ` [PATCH 20/23] usb: xhci: simplify Max Scratchpad buffer macros Mathias Nyman
2025-11-19 14:24 ` [PATCH 21/23] usb: xhci: drop xhci-caps.h dependence on xhci-ext-caps.h Mathias Nyman
2025-11-19 14:24 ` [PATCH 22/23] usb: xhci: standardize single bit-field macros Mathias Nyman
2025-11-19 14:24 ` [PATCH 23/23] usb: xhci: Add debugfs support for xHCI Port Link Info (PORTLI) register Mathias Nyman
2026-03-04  9:42   ` Michal Pecio
2026-03-04 14:25     ` Mathias Nyman
2026-03-04 16:40       ` Michal Pecio

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