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// #========================================================================

// #

// #    mem285.S

// #

// #    StrongARM EBSA-285 memory setup

// #

// #========================================================================

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// -------------------------------------------

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// #========================================================================

// ######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 

#include 

        .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 */