Messages in this thread | | | Subject | Re: [PATCH] xhci: Use ffs() to find page size in xhci_mem_init() | From | Mathias Nyman <> | Date | Thu, 7 Feb 2019 12:46:45 +0200 |
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On 07.02.2019 11:06, Felipe Balbi wrote: > > Hi, > > Mathias Nyman <mathias.nyman@linux.intel.com> writes: >> On 07.02.2019 02:03, Andrey Smirnov wrote: >>> Get page size order using ffs() instead of open coding it with a loop. >>> >>> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com> >>> Cc: Mathias Nyman <mathias.nyman@intel.com> >>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >>> Cc: linux-usb@vger.kernel.org >>> Cc: linux-kernel@vger.kernel.org >>> --- >>> 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..44b43c3d819f 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 = ffs(page_size); >>> if (i < 16) >>> xhci_dbg_trace(xhci, trace_xhci_dbg_init, >>> "Supported page size of %iK", (1 << (i+12)) / 1024); >> >> Hi >> >> using ffs() is a welcome change, but it will give different a result than the loop. >> >> *old loop >> valid page_size value if i < 16 >> *ffs() >> valid page_size value if i >= 1 and i < 17 > > off-by-one, just use i = ffs() - 1. Or use __ffs(). >
and handle the page_size == 0 case.
-Mathias
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