Re: [LinuxBIOS] do_ram_command

[Corey Osgood]

Joseph Smith wrote:
> Hello,
> Corey or Uwe maybe you can help me with this. Does this look workable to you?
> I'm just not sure with all this bit shifting it is going to return the  
> correct value. The DRC register has seperate bits for the commands and  
> the refreshes.
>
> /* DRC[10:8] - Refresh Mode Select (RMS). */
> #define RAM_COMMAND_REFRESH_1	 0x1 /* Refresh interval 15.6 us for 133MHz */
> #define RAM_COMMAND_REFRESH_2	 0x2 /* Refresh interval 7.8 us for 133MHz */
> #define RAM_COMMAND_REFRESH_3  0x7 /* Refresh interval 128 Clocks.  
> (Fast Refresh Mode) */
>
> /* DRC[6:4] - SDRAM Mode Select (SMS). */
> #define RAM_COMMAND_NOP		 0x1
> #define RAM_COMMAND_PRECHARGE	 0x2
> #define RAM_COMMAND_MRS		 0x3
> #define RAM_COMMAND_CBR		 0x6
> #define RAM_COMMAND_NORMAL	 0x7
>
> static void do_ram_command(const struct mem_controller *ctrl, uint32_t  
> command,
>    		   uint32_t addr_offset, uint32_t row_offset)
> {
>    int i;

not used? my fault, not yours, it can be dropped.
> uint32_t reg;
>
> /* TODO: Support for multiple DIMMs. */
>
> /* Configure the RAM command. */
>    reg = pci_read_config32(ctrl->d0, DRC);
>    reg &= 0x0;		/* Clear all bits to default: 00000000h. */

you want to make this 0xdffff00f or something similar. That way, you're
only clearing the bits that you're not affecting, especially if they're
marked reserved. Other than that, looks good, but I've forgotten which
northbridge this is for so I haven't checked the datasheet.

-Corey
> reg |= command << 4;
>        /* If RAM_COMMAND_NORMAL set the refresh mode and IC bit 29. */
>    if (command == RAM_COMMAND_NORMAL) {
>    reg |= ((RAM_COMMAND_REFRESH_1 << 8) | (1 << 29));
>        }
>    pci_write_config32(ctrl->d0, DRC, reg);
>
> /* RAM_COMMAND_NORMAL affects only the memory controller and
>       doesn't need to be "sent" to the DIMMs. */
>    /* if (command == RAM_COMMAND_NORMAL) return; */
>
> PRINT_DEBUG("    Sending RAM command 0x");
>    PRINT_DEBUG_HEX32(reg);
>    PRINT_DEBUG(" to 0x");
>    PRINT_DEBUG_HEX32(0 + addr_offset); // FIXME
>    PRINT_DEBUG("\r\n");
>
> /* Read from (DIMM start address + addr_offset). */
>    read32(0 + addr_offset);	//first offset is always 0
>    read32(row_offset + addr_offset);
> }
>
> Thanks - Joe