1. 17 Feb, 2011 26 commits
  2. 04 Feb, 2011 3 commits
    • Stephen Boyd's avatar
      hvc_dcc: Simplify assembly for v6 and v7 ARM · 8e6d3fe1
      Stephen Boyd authored
      The inline assembly differences for v6 vs. v7 in the hvc_dcc
      driver are purely optimizations. On a v7 processor, an mrc with
      the pc sets the condition codes to the 28-31 bits of the register
      being read. It just so happens that the TX/RX full bits the DCC
      driver is testing for are high enough in the register to be put
      into the condition codes. On a v6 processor, this "feature" isn't
      implemented and thus we have to do the usual read, mask, test
      operations to check for TX/RX full.
      
      Since we already test the RX/TX full bits before calling
      __dcc_getchar() and __dcc_putchar() we don't actually need to do
      anything special for v7 over v6. The only difference is in
      hvc_dcc_get_chars(). We would test RX full, poll RX full, and
      then read a character from the buffer, whereas now we will test
      RX full, read a character from the buffer, and then test RX full
      again for the second iteration of the loop. It doesn't seem
      possible for the buffer to go from full to empty between testing
      the RX full and reading a character. Therefore, replace the v7
      versions with the v6 versions and everything works the same.
      Acked-by: default avatarTony Lindgren <tony@atomide.com>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Acked-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
      Cc: Daniel Walker <dwalker@codeaurora.org>
      Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
      8e6d3fe1
    • Stephen Boyd's avatar
      hvc_dcc: Simplify put_chars()/get_chars() loops · bf73bd35
      Stephen Boyd authored
      Casting and anding with 0xff is unnecessary in
      hvc_dcc_put_chars() since buf is already a char[].
      __dcc_get_char() can't return an int less than 0 since it only
      returns a char. Simplify the if statement in hvc_dcc_get_chars()
      to take this into account.
      
      Cc: Daniel Walker <dwalker@codeaurora.org>
      Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
      bf73bd35
    • Stephen Boyd's avatar
      hvc_dcc: Fix bad code generation by marking assembly volatile · a9963201
      Stephen Boyd authored
      Without marking the asm __dcc_getstatus() volatile my compiler
      decides it can cache the value of __ret in a register and then
      check the value of it continually in hvc_dcc_put_chars() (I had
      to replace get_wait/put_wait with 1 and fixup the branch
      otherwise my disassembler barfed on __dcc_(get|put)char).
      
      00000000 <hvc_dcc_put_chars>:
         0:   ee103e11        mrc     14, 0, r3, cr0, cr1, {0}
         4:   e3a0c000        mov     ip, #0  ; 0x0
         8:   e2033202        and     r3, r3, #536870912      ; 0x20000000
         c:   ea000006        b       2c <hvc_dcc_put_chars+0x2c>
        10:   e3530000        cmp     r3, #0  ; 0x0
        14:   1afffffd        bne     10 <hvc_dcc_put_chars+0x10>
        18:   e7d1000c        ldrb    r0, [r1, ip]
        1c:   ee10fe11        mrc     14, 0, pc, cr0, cr1, {0}
        20:   2afffffd        bcs     1c <hvc_dcc_put_chars+0x1c>
        24:   ee000e15        mcr     14, 0, r0, cr0, cr5, {0}
        28:   e28cc001        add     ip, ip, #1      ; 0x1
        2c:   e15c0002        cmp     ip, r2
        30:   bafffff6        blt     10 <hvc_dcc_put_chars+0x10>
        34:   e1a00002        mov     r0, r2
        38:   e12fff1e        bx      lr
      
      As you can see, the value of the mrc is checked against
      DCC_STATUS_TX (bit 29) and then stored in r3 for later use.
      Marking the asm volatile produces the following:
      
      00000000 <hvc_dcc_put_chars>:
         0:   e3a03000        mov     r3, #0  ; 0x0
         4:   ea000007        b       28 <hvc_dcc_put_chars+0x28>
         8:   ee100e11        mrc     14, 0, r0, cr0, cr1, {0}
         c:   e3100202        tst     r0, #536870912  ; 0x20000000
        10:   1afffffc        bne     8 <hvc_dcc_put_chars+0x8>
        14:   e7d10003        ldrb    r0, [r1, r3]
        18:   ee10fe11        mrc     14, 0, pc, cr0, cr1, {0}
        1c:   2afffffd        bcs     18 <hvc_dcc_put_chars+0x18>
        20:   ee000e15        mcr     14, 0, r0, cr0, cr5, {0}
        24:   e2833001        add     r3, r3, #1      ; 0x1
        28:   e1530002        cmp     r3, r2
        2c:   bafffff5        blt     8 <hvc_dcc_put_chars+0x8>
        30:   e1a00002        mov     r0, r2
        34:   e12fff1e        bx      lr
      
      which looks better and actually works. Mark all the inline
      assembly in this file as volatile since we don't want the
      compiler to optimize away these statements or move them around
      in any way.
      Acked-by: default avatarTony Lindgren <tony@atomide.com>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Acked-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
      Cc: Daniel Walker <dwalker@codeaurora.org>
      Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
      a9963201
  3. 03 Feb, 2011 11 commits