DSP

TI C66x DSP硬件信号量 - 3(Direct Semaphore)

2019-07-13 20:12发布

站内文章 / DSP
13156 0 1038
Direct request is the simplest method used to request a semaphore. The request behaves as an atomic read and set operation. The result of a request is either to grant the semaphore to the requesting core or deny the request because the semaphore has already been granted to another core. A direct request is issued by reading the SEM_DIRECT register corresponding to the semaphore requested, there are 64 DIRECT registers, one corresponding to each of the 64 semaphores. If the semaphore is free, the read returns “0x1”; if the request is rejected, the read returns the ID of the core that currently owns the semaphore. No semaphore grant (SEMINTn) interrupts are generated when the direct request method is used. However, an error interrupt may be generated. Direct Semaphore register: There are 64 direct registers. Each one is associated with and used to manage the respective semaphore.   Direct Register (SEM_DIRECTn): 读与写该寄存器时，Free域的意义不同。 WaitHwSem :Waits until requested semaphore is free. Function is blocking, so it will wait until requested semaphore is free and calling  EU is not suspended during the wait time. code: #define HWSEM_DIRECT_REG_ADDRESS   (volatile u32*)(0x02640100) //0x02640100为SEM_DIRECT0的地址，SEM_DIRECTn的地址为HWSEM_DIRECT_REG_ADDRESS +n u32  WaitHwSem(const u32 semId) //请求信号量 {     u32 retVal;     u32 semId;     volatile u32  reg;                    retVal = NoError;     if( semId < 64) //64为硬件信号量number     {                   do                   {                              reg =*(HWSEM_DIRECT_REG_ADDRESS +semId);  //读寄存器                    } while ((reg &1) !=1);     }     else  retVal = InvalidValue;     return retVal; } FreeHwSem :This function unlocks the semaphore. If there are other CPUs waiting the semaphore then thefirst CPU(first-in-first-out)and EU waiting for the semaphore is allowed to return successfully from its call to WaitHwSem(). code: volatile u32 DirectSEM[64];  //64个直接信号量SEM_DIRECT0~63寄存器地址 u32  FreeHwSem(const u32 semId)  //释放信号量 {     u32 retVal;     u32 semId;                    retVal = NoError;     if(semId < 64) //64为硬件信号量number     {        DirectSEM[semId] = 1;  //写寄存器     }     else  EHwSemRetVal_InvalidValue;     return retVal; } Direct semapore用法： WaitHwSem(semId);  Access shared resource code;             //对于Nyqusit来说，如果四个CPU共享同一段内存，那么需要为该段内存reserve一个硬             //件信号量semId，当某个CPU访问这段内存的时候，需要采用类似的代码,用semId信号             //量进行保护共享内存，实现只允许同时只有一个CPU在访问。 FreeHwSem(semId);

热门文章