powerpc/mpc8xxx: Allow override DDR read-to-write turnaround time

Add this option to allow boards to override the default read-to-write
turnaround time for better performance.

Signed-off-by: York Sun <yorksun@freescale.com>

diff --git a/arch/powerpc/cpu/mpc8xxx/ddr/ctrl_regs.c b/arch/powerpc/cpu/mpc8xxx/ddr/ctrl_regs.c
index 02d069c..3824aad 100644 (file)
--- a/arch/powerpc/cpu/mpc8xxx/ddr/ctrl_regs.c
+++ b/arch/powerpc/cpu/mpc8xxx/ddr/ctrl_regs.c
@@ -267,6 +267,9 @@ static void set_timing_cfg_0(fsl_ddr_cfg_regs_t *ddr,
        tmrd_mclk = 2;
 #endif
 
+       if (popts->trwt_override)
+               trwt_mclk = popts->trwt;
+
        ddr->timing_cfg_0 = (0
                | ((trwt_mclk & 0x3) << 30)     /* RWT */
                | ((twrt_mclk & 0x3) << 28)     /* WRT */

diff --git a/arch/powerpc/include/asm/fsl_ddr_sdram.h b/arch/powerpc/include/asm/fsl_ddr_sdram.h
index 1778cc5..bc063ea 100644 (file)
--- a/arch/powerpc/include/asm/fsl_ddr_sdram.h
+++ b/arch/powerpc/include/asm/fsl_ddr_sdram.h
@@ -271,6 +271,9 @@ typedef struct memctl_options_s {
        unsigned int rcw_2;
        /* control register 1 */
        unsigned int ddr_cdr1;
+
+       unsigned int trwt_override;
+       unsigned int trwt;                      /* read-to-write turnaround */
 } memctl_options_t;
 
 extern phys_size_t fsl_ddr_sdram(void);