Messages in this thread | | | Date | Mon, 22 Jun 2015 08:16:43 -0500 | From | Timur Tabi <> | Subject | Re: [PATCH] ARM64: TTY: hvc_dcc: Add support for ARM64 dcc |
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Will Deacon wrote: > On Fri, Jun 19, 2015 at 11:08:54PM +0100, Timur Tabi wrote: >> From: Abhimanyu Kapur <abhimany@codeaurora.org> >> >> Add support for debug communications channel based >> hvc console for arm64 cpus. > > I still think we should be disabling userspace access to the DCC if the > kernel is using it as its console.
I don't disagree, I just don't know how to do that.
>> + * A call to __dcc_getchar() or __dcc_putchar() is typically followed by >> + * a call to __dcc_getstatus(). We want to make sure that the CPU does >> + * not speculative read the DCC status before executing the read or write >> + * instruction. That's what the ISBs are for. >> + * >> + * The 'volatile' ensures that the compiler does not cache the status bits, >> + * and instead reads the DCC register every time. >> + */ > > Missing header guards.
Will fix.
>> +#include <asm/barrier.h> >> + >> +static inline u32 __dcc_getstatus(void) >> +{ >> + u32 __ret; >> + >> + asm volatile("mrs %0, mdccsr_el0" : "=r" (__ret) >> + : : "cc"); > > You don't need the "cc" clobber.
Will fix.
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