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// #========================================================================
// #
// #    mem285.S
// #
// #    StrongARM EBSA-285 memory setup
// #
// #========================================================================
// ####ECOSGPLCOPYRIGHTBEGIN####                                            
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//
// As a special exception, if other files instantiate templates or use      
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// General Public License v2.                                               
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// ####ECOSGPLCOPYRIGHTEND####                                              
// #========================================================================
// ######DESCRIPTIONBEGIN####
// #
// # Author(s):     Red Hat, hmt
// # Contributors:  Red Hat, hmt
// # Date:          1999-07-05
// # Purpose:       StrongARM EBSA-285 SDRAM initialization
// # Description:   SDRAM Initialization for Intel(R) SA-110 21285 Companion
// #                Chip
// #                Intel is a Registered Trademark of Intel Corporation.
// #                Other Brands and Trademarks are the property of their
// #                respective owners.        
// #
// #####DESCRIPTIONEND####
// #
// #========================================================================

//      .file "mem285.S"
        .title "SDRAM Init for Intel(R) SA-110 21285 Companion Chip"

#include <cyg/hal/hal_ebsa285.h>

#include <pkgconf/system.h>

        .text
        .align     4

#define ARRAY_0_MODE_REGISTER     (SA110_SDRAM_ARRAY_0_MODE_REGISTER_BASE)
#define ARRAY_1_MODE_REGISTER     (SA110_SDRAM_ARRAY_1_MODE_REGISTER_BASE)

#define MODE_REGISTER_STEP (ARRAY_1_MODE_REGISTER - ARRAY_0_MODE_REGISTER)

        // [6:4] /CAS Latency is 2 (2)
        // [ 3 ] Burst Type is 0, Sequential
        // [2:0] Burst Length is 2, meaning 4
#define SDRAM_MODE_REGISTER_SETUP 0x22
        // Shifted left 2 because this is a word-address-offset!
#define SDRAM_MODE_REGISTER_SETUP_OFFSET ((SDRAM_MODE_REGISTER_SETUP) << 2)

        
#define SDRAM_TIMING_VALUE        (SA110_SDRAM_ROW_PRECHARGE_2_CYCLES    | \
                                   SA110_SDRAM_LAST_DATA_IN_3_CYCLES     | \
                                   SA110_SDRAM_RAS_TO_CAS_DELAY_2_CYCLES | \
                                   SA110_SDRAM_CAS_LATENCY_2_CYCLES      | \
                                   SA110_SDRAM_ROW_CYCLE_TIME_4_CYCLES   | \
                                   SA110_SDRAM_COMMAND_DRIVE_SAME_CYCLE)

#define SDRAM_TIMING_VALUE_MIN    (SDRAM_TIMING_VALUE                    | \
                                   SA110_SDRAM_REFRESH_INTERVAL_MIN)

#define SDRAM_TIMING_VALUE_NORMAL (SDRAM_TIMING_VALUE                    | \
                                   SA110_SDRAM_REFRESH_INTERVAL_NORMAL)



        /*
         * This subroutine sizes and configures up to four banks of SDRAM DIMMs.
         * It runs early without a stack.
         *
         * R0 - R9 are destroyed. All others preserved.
         * Except r11 which is also destroyed.
         *
         */
        .global __mem285_init
__mem285_init:

        /*
         * First we find out whether the SDRAMs are already initialized,
         * and if so, leave them alone.  RAM start implies just do the
         * sizing sums to return top of memory.
         */
        ldr     r0, =SA110_CONTROL_STATUS_BASE

#ifndef CYG_HAL_STARTUP_RAM
        // This is conditional even in ROM start for
        // a) testing ROM images eg. stubs in RAM really
        // b) cooperation with eg. POST code, so we are not really at reset
        ldr     r0, =SA110_CONTROL_STATUS_BASE
        ldr     r1, [r0, #SA110_SDRAM_TIMING_o]
        ldr     r2, =SDRAM_TIMING_VALUE_NORMAL
        cmps    r1, r2
        movne   r11, #0
        bne     12f
#endif  // ! defined CYG_HAL_STARTUP_RAM

        // Add up the sizes and return in r0:
        mov     r1, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_0_o
        mov     r2, #0
        mov     r3, #1
    1:
        ldr     r4, [r0, r1]
        ands    r4, r4, #7              // if zero, no mem here
        addne   r2, r2, r3, asl r4      // tot up array sizes (in 1/2 Megs)
        add     r1, r1, #4
        cmps    r1, #(SA110_SDRAM_ADDRESS_SIZE_ARRAY_3_o + 4)
        blt     1b

        mov     r0, r2, asl #19         // get size into Mb
        mov     pc, lr

#ifndef CYG_HAL_STARTUP_RAM

    12:
        /*
         * Write to the SDRAM Timing Register in the 21285.  Disable
         * refresh totally.
         */
        mov     r1, #0
        str     r1, [r0, #SA110_SDRAM_TIMING_o]

        // Disable each array
        mov     r1, #0
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_0_o]
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_1_o]
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_2_o]
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_3_o]
        
        // Wait for 8 refresh cycles to complete
        mov     r1, #(9 * 32)
    1:  subs    r1, r1, #1
        bpl     1b

        /*
         * Force an all-banks recharge on all four SDRAM arrays
         *
         * This code came from the SA-IOP ver 1.0 (3-16-98) spec pg 22
         *
         * You must access all four arrays regardless of whether there is
         * memory there because the 21285 counts the precharge accesses and
         * inhibits access to the SDRAM until all four have been done.
         *
         * An all banks rechargs is initiated by a read from any address
         * in the mode register space.
         */

        mov     r1, #3 
        mov     r0, #ARRAY_0_MODE_REGISTER
   1:
        ldr     r2, [r0]
        add     r0, r0, #MODE_REGISTER_STEP
        subs    r1, r1, #1
        bpl     1b

        /*
         * Now we need to write to the SDRAM Mode Register.
         * The address is important, not the data.  The mode register
         * should be configured for a burst size of 4 with linear addressing
         */
        mov     r1, #3
        mov     r0, #ARRAY_0_MODE_REGISTER
   1:
        str     r0, [r0, #SDRAM_MODE_REGISTER_SETUP_OFFSET]
        add     r0, r0, #MODE_REGISTER_STEP
        subs    r1, r1, #1
        bpl     1b
        
        /*
         * Write to the SDRAM Timing Register in the 21285.  Set the
         * refresh interval to the minimum because we have to wait for
         * 8 refresh cycles to complete before we can rely on the SDRAMs
         * to be operating normally
         */
        ldr     r0, =SA110_CONTROL_STATUS_BASE
        ldr     r1, =SDRAM_TIMING_VALUE_MIN
        str     r1, [r0, #SA110_SDRAM_TIMING_o]

        // Disable each array
        mov     r1, #0
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_0_o]
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_1_o]
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_2_o]
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_3_o]
        
        // Wait for 8 refresh cycles to complete
        mov     r1, #(9 * 32)
    1:  subs    r1, r1, #1
        bpl     1b

        // Now reset the Refresh interval to a sensible value
        ldr     r1, =SDRAM_TIMING_VALUE_NORMAL
        str     r1, [r0, #SA110_SDRAM_TIMING_o]
        
        /* start out assuming 64M part with MUX mode 2 */
        mov     r1, #(SA110_SDRAM_SIZE_64MB | SA110_SDRAM_MUX_MODE2)
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_0_o]
        add     r1, r1, #(64 << 20) // Add 64Mb
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_1_o]
        add     r1, r1, #(64 << 20) // Add 64Mb again
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_2_o]
        add     r1, r1, #(64 << 20) // Add 64Mb and again
        str     r1, [r0, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_3_o]
        
        /*
         * First, try to figure out which banks are populated and
         * the real mux mode for those banks.
         *
         * At this point:
         *   r0 - Base of control/status registers
         *
         * Register usage:
         *   r8 - offset to SDRAM addr/size register
         *   r5 - pattern
         *   r4 - inverse pattern
         *   r3 - scratch/mux mode output
         *   r2 - scratch offset
         *   r1 - base address of 64M block in consideration
         *   r0 - base address of control register sets
         */     
        mov     r8, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_0_o
        mov     r1, #0

        ldr     r5, =0x12345678
        mvn     r4, r5

    20:
        str     r5, [r1]      // Offset 0 should work regardless
        str     r4, [r1, #4]  // put something else on the data bus
        ldr     r3, [r1]      // read back original
        cmps    r3, r5

        // If we didn't read pattern, then no memory present
        movne   r3, #0
        strne   r3, [r0, r8]            // write to addr/size register
        bne     49f                     // straight to next loop

        /*
         * This bank is populated, so try to determine mux mode.
         * All banks are currently set for mux mode 2.
         */

        // A21 having no effect distinguishes the need for mux mode 0.
        str     r5, [r1]
        mov     r2, #(1 << 21)
        str     r4, [r1, r2]   // Store bad value at A21 mirror address
                                 // expect to trash value at r1 if mode 0
        ldr     r3, [r1]
        cmps    r3, r5
        // If we don't read back pattern, then its mux mode 0
        
        // Force to 32M size to include A18 when sizing:
        movne   r3, #(SA110_SDRAM_SIZE_32MB | SA110_SDRAM_MUX_MODE0)
        bne     2f

        // A23 having effect distinguishes the need for mux mode 2.
        str     r5, [r1]
        mov     r2, #(1 << 23)
        str     r4, [r1, r2]   // Store bad value at A23 mirror address
                               // expect to preserve value at r1 if mode 2
        ldr     r3, [r1]
        cmps    r3, r5
        // if pattern still there, then mode 2
        moveq   r3, #(SA110_SDRAM_SIZE_64MB | SA110_SDRAM_MUX_MODE2)
        beq     2f

        // A22 having effect distinguishes the need for mux mode 4.
        str     r5, [r1]
        mov     r2, #(1 << 22)
        str     r4, [r1, r2]   // Store bad value at A22 mirror address
                               // expect to preserve value at r1 if mode 4
        ldr     r3, [r1]
        cmps    r3, r5
        // if pattern A still there, then mode 4
        moveq   r3, #(SA110_SDRAM_SIZE_64MB | SA110_SDRAM_MUX_MODE4)
        beq     2f

        /*
         * At this point it is either mode 1 or 3. There is no clear cut
         * test to differentiate the two, so make a best guess now, then
         * correct later (if necessary) while sizing the bank.
         */

        // NB the bank is still in mux mode 2, so A24 is fed to the wire for
        // A22 (mode 1) or no-connection (mode 3); so:
        // A24 having effect distinguishes the need for mux mode 1
        // A24 having no effect distinguishes the need for mux mode 3
        str     r5, [r1]
        mov     r2, #(1 << 24)
        str     r4, [r1, r2]
        ldr     r3, [r1]
        cmps    r3, r5
        // If pattern, try mode 1
        moveq   r3, #(SA110_SDRAM_SIZE_64MB | SA110_SDRAM_MUX_MODE1)
        // otherwise, try mode 3
        movne   r3, #(SA110_SDRAM_SIZE_64MB | SA110_SDRAM_MUX_MODE3)

        bne 2f

    2:
        orr     r3, r3, r1                      // add in base address
        str     r3, [r0, r8]                    // write to addr/size register
        
        /*
         * Now that mux mode for this array is (hopefully) setup, we can try
         * to size this SDRAM array.
         * 
         * Register usage:
         *    r8 - offset to current size/mode register
         *    r1 - offset to current base (in 64M blocks)
         *    r0 - base address of control register sets
         */

        mov     r4, #(63 << 20)         // 63Mb to start with
    1:  str     r4, [r1, r4]
        subs    r4, r4, #(1 << 20)      // go down in increments of 1Mb
        bpl     1b

        str     r4, [r1, #4]            // change pattern on data bus

        // search for first unexpected data in ascending order
        mov     r4, #0
    1:
        ldr     r5, [r1, r4]
        cmps    r5, r4
        bne     23f                     // different so end of array
        add     r4, r4, #(1 << 20)      // go up in increments of 1Mb
        cmps    r4, #(64 << 20)
        blt     1b
        // fall-through assumes it is a 64Mb device
   23:  
        movs    r4, r4, lsr #20         // get a plain number of Mb
        // if this gave a zero, maybe we were mistaken about the RAM
        // working earlier: disable this bank.
        streq   r4, [r0, r8]            // write to addr/size register
        beq     49f                     // straight to next loop

        // apparently, mode 3 devices *must* be 8Mb; if we got a different
        // answer, set it to mode 1 and go back to try again:
        cmps    r4, #8
        beq     4f

        // skip if 8Mb; we are happy
        ldr     r3, [r0, r8]            // read in the mode we set
        and     r3, r3, #SA110_SDRAM_MUX_MODE_MASK
        cmp     r3, #SA110_SDRAM_MUX_MODE3
        // Must be misconfigured mux mode. Set to mode 1 and retry
        moveq   r3, #(SA110_SDRAM_SIZE_64MB | SA110_SDRAM_MUX_MODE1)
        beq     2b
        // not mux mode 3; drop though OK

    4:
        // convert MB size to register size val
        mov     r5, #0
        mov     r3, r4
    5:  movs    r3, r3, lsr #1
        add     r5, r5, #1
        bcc     5b

        // Double check that the size was a power of 2
        mov     r6, #1
        mov     r6, r6, lsl r5          // should get Mb count back doubled
        cmps    r6, r4, lsl #1          // compare with doubled
        movne   r5, #0                  // disable this bank
        ldr     r3, [r0, r8]            // Load current setting
        bic     r3, r3, #7
        orr     r3, r3, r5              // insert the correct size code
        str     r3, [r0, r8]            // into the control register

   49:
        add     r8, r8, #4                      // next addr/size register
        add     r1, r1, #(64<<20)               // next array
        cmps    r1, #(256<<20)                  // top address + 1 bank
        blt     20b
        // END of main loop to size all 4 DRAM banks

        /*
         * At this point, the size values are all in the control registers.
         *
         * We want to set memory up to be contiguous. Since the
         * banks' base address needs to be naturally aligned, we
         * need to sort the bank sizes from large to small.
         *
         * Register usage:
         *   r0 - base address of control register sets
         *   r1 - bitmap of which slots we have covered in toto
         *   r2 - cumulative base address of mapped SDRAM
         *   r3 - biggest size code this pass
         *   r4 - bit index of current slot
         *   r5 - bit index of biggest slot found this pass
         *   r6 - scratch control reg contents
         *   r7 - scratch size code
         *   r8 - address of current slot's control register
         *   r9 - address of biggest slot found's control register
         */
        mov     r1, #0                  // bitmap of which we have covered
        mov     r2, #0                  // cumulative base address
        // do... until there are no more slots to deal with
    70:
        mov     r3, #0                  // biggest this pass
        mov     r4, #1                  // bit index of current slot
        mov     r5, #0                  // bit index of biggest slot found
        mov     r8, #SA110_SDRAM_ADDRESS_SIZE_ARRAY_0_o
        mov     r9, #0                  // address of biggest slot found
        // Foreach slot we have not yet dealt with
    75:
        tst     r4, r1
        bne     88f
        ldr     r6, [r0, r8]
        and     r7, r6, #7
        cmps    r7, r3
        movgt   r3, r7                  // save biggest's size
        movgt   r5, r4                  // save biggest's index
        movgt   r9, r8                  // save biggest's reg address
    88:
        mov     r4, r4, asl #1
        add     r8, r8, #4
        cmps    r4, #0x10
        blt     75b                     // next slot
        // Did we find a largest slot?
        cmps    r5, #0
        beq     95f     // No!  Finished

        orr     r1, r1, r5              // can forget r4 and r5 now
        ldr     r6, [r0, r9]            // get the control register
        bic     r6, r6, #0x0ff00000     // clear base address bits
        orr     r6, r6, r2              // insert base address to use
        str     r6, [r0, r9]            // store the new control register
        mov     r6, #1
        mov     r6, r6, asl r3
        mov     r6, r6, asl #19         // 1 << (size-code + 19) is size
        add     r2, r2, r6              // increment the cumulating address

        b       70b                     // go look for the next one

    95: // all done!
        // at this point, r2 contains the top of memory.
        // (r11 is the value from last time or zero if first time)

        cmps    r11, r2                 // Same answer as last time?
        movne   r11, r2                 // if not, save memsize
        bne     12b                     // ...and try again.
        
        mov     r0, r2
        mov     pc, lr  
#endif // ! defined CYG_HAL_STARTUP_RAM
//FUNC_END __mem285_init

/* EOF mem285.S */