linux-kernel - [PATCH v2] xhci: Use __ffs() to find page size in xhci_mem

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Message-Id: <20190208014854.22437-1-andrew.smirnov@gmail.com>
Date:   Thu,  7 Feb 2019 17:48:54 -0800
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     linux-usb@...r.kernel.org
Cc:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] xhci: Use __ffs() to find page size in xhci_mem_init()

Get page size order using __ffs() instead of open coding it with a loop.

Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
Cc: Mathias Nyman <mathias.nyman@...el.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---

Changes since [v1]:

    - Code changed to use __ffs()
    - Added check for page_size == 0

[v1] https://lore.kernel.org/lkml/20190207000349.7816-1-andrew.smirnov@gmail.com

 drivers/usb/host/xhci-mem.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 36a3eb8849f1..4b350125e1cc 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -2362,11 +2362,7 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags)
 	page_size = readl(&xhci->op_regs->page_size);
 	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
 			"Supported page size register = 0x%x", page_size);
-	for (i = 0; i < 16; i++) {
-		if ((0x1 & page_size) != 0)
-			break;
-		page_size = page_size >> 1;
-	}
+	i = page_size ? __ffs(page_size) : INT_MAX;
 	if (i < 16)
 		xhci_dbg_trace(xhci, trace_xhci_dbg_init,
 			"Supported page size of %iK", (1 << (i+12)) / 1024);
-- 
2.20.1