RE: [PATCH v4 1/2] OMAP3: SDRC: Dynamic Calculation of SDRC stall latency during DVFS

G, Manjunath Kondaiah
2010-03-18T06:17:57Z

> -----Original Message-----
> From: linux-omap-owner@vger.kernel.org
> [mailto:linux-omap-owner@vger.kernel.org] On Behalf Of Gurav , Pramod
> Sent: Thursday, March 18, 2010 10:26 AM
> To: linux-omap@vger.kernel.org
> Cc: Reddy, Teerth; Gurav , Pramod; Sripathy, Vishwanath
> Subject: [PATCH v4 1/2] OMAP3: SDRC: Dynamic Calculation of
> SDRC stall latency during DVFS
>
> From: Teerth Reddy <teerth@ti.com>
>
> The patch has the changes to calculate the dpll3 clock stabilization
> delay dynamically. The SRAM delay is calibrated during bootup
> using the
> gptimers and used while calculating the stabilization delay. By using
> the dynamic method the dependency on the type of cache being used is
> removed.
>
> The wait time for L3 clock stabilization is calculated using
> the formula
> = 4*REFCLK + 8*CLKOUTX2,
> which uses the M, N and M2 read from the registers.
> Since this gives slightly less value, 2us is added as buffer
> for safety.
> This works fine for omap3.
>
> Signed-off-by: Teerth Reddy <teerth@ti.com>
> Signed-off-by: Pramod Gurav <pramod.gurav@ti.com>
> Signed-off-by: Vishwanath Sripathy <vishwanath.bs@ti.com>
>
> ---
> arch/arm/mach-omap2/clkt34xx_dpll3m2.c | 54
> +++++++++++++++++++++++++++-----
> arch/arm/mach-omap2/clock34xx.h | 2 +
> arch/arm/mach-omap2/clock3xxx.c | 2 +-
> arch/arm/mach-omap2/clock3xxx.h | 1 +
> arch/arm/mach-omap2/clock3xxx_data.c | 13 ++++++++
> arch/arm/mach-omap2/sram34xx.S | 8 +++++
> arch/arm/plat-omap/include/plat/sram.h | 4 ++
> arch/arm/plat-omap/sram.c | 51
> ++++++++++++++++++++++++++++++
> 8 files changed, 126 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/clkt34xx_dpll3m2.c
> b/arch/arm/mach-omap2/clkt34xx_dpll3m2.c
> index b2b1e37..29421b1 100644
> --- a/arch/arm/mach-omap2/clkt34xx_dpll3m2.c
> +++ b/arch/arm/mach-omap2/clkt34xx_dpll3m2.c
> @@ -24,13 +24,21 @@
> #include <plat/clock.h>
> #include <plat/sram.h>
> #include <plat/sdrc.h>
> +#include <plat/prcm.h>
>
> #include "clock.h"
> #include "clock3xxx.h"
> #include "clock34xx.h"
> #include "sdrc.h"
>
> -#define CYCLES_PER_MHZ 1000000
> +#define CYCLES_PER_MHZ 1000000
> +
> +#define DPLL_M_MASK 0x7ff
> +#define DPLL_N_MASK 0x7f

Use one more tab

> +#define DPLL_M2_MASK 0x1f
> +#define SHIFT_DPLL_M 16
> +#define SHIFT_DPLL_N 8
> +#define SHIFT_DPLL_M2 27
>
> /*
> * CORE DPLL (DPLL3) M2 divider rate programming functions
> @@ -56,6 +64,11 @@ int omap3_core_dpll_m2_set_rate(struct clk
> *clk, unsigned long rate)
> struct omap_sdrc_params *sdrc_cs0;
> struct omap_sdrc_params *sdrc_cs1;
> int ret;
> + u32 clk_sel_regval;
> + u32 core_dpll_mul_m, core_dpll_div_n, core_dpll_clkoutdiv_m2;
> + u32 sys_clk_rate, sdrc_clk_stab;
> + u32 refclk, clkoutx2, switch_latency;
> + unsigned int delay_sram;
>
> if (!clk || !rate)
> return -EINVAL;
> @@ -79,16 +92,41 @@ int omap3_core_dpll_m2_set_rate(struct
> clk *clk, unsigned long rate)
> unlock_dll = 1;
> }
>
> + clk_sel_regval = __raw_readl(clk->clksel_reg);
> +
> + /* Get the M, N and M2 values required for getting sdrc
> clk stab */
> + core_dpll_mul_m = (clk_sel_regval >> SHIFT_DPLL_M) &
> DPLL_M_MASK;
> + core_dpll_div_n = (clk_sel_regval >> SHIFT_DPLL_N) &
> DPLL_N_MASK;
> + core_dpll_clkoutdiv_m2 = (clk_sel_regval >> SHIFT_DPLL_M2) &
> + DPLL_M2_MASK;
> + sys_clk_rate = clk_get_rate(sys_ck_p);
> +
> + sys_clk_rate = sys_clk_rate / CYCLES_PER_MHZ;
> +
> + /* wait time for L3 clk stabilization = 4*REFCLK + 8*CLKOUTX2 */
> + refclk = (4 * (core_dpll_div_n + 1)) / sys_clk_rate;
> + clkoutx2 = ((core_dpll_div_n + 1) * core_dpll_clkoutdiv_m2) /
> + (sys_clk_rate *
> core_dpll_mul_m * 2);
> + switch_latency = refclk + 8 * clkoutx2;
> +
> + /* Adding 2us to sdrc clk stab */
> + sdrc_clk_stab = switch_latency + 2;
> +
> + delay_sram = delay_sram_val();
> +
> /*
> - * XXX This only needs to be done when the CPU frequency changes
> + * Calculate the number of MPU cycles
> + * to wait for SDRC to stabilize
> */
> +
> _mpurate = arm_fck_p->rate / CYCLES_PER_MHZ;
> - c = (_mpurate << SDRC_MPURATE_SCALE) >> SDRC_MPURATE_BASE_SHIFT;
> - c += 1; /* for safety */
> - c *= SDRC_MPURATE_LOOPS;
> - c >>= SDRC_MPURATE_SCALE;
> - if (c == 0)
> - c = 1;
> +
> + c = ((sdrc_clk_stab * _mpurate) / (delay_sram * 2));
> +
> + pr_debug("m = %d, n = %d, m2 =%d\n", core_dpll_mul_m,
> core_dpll_div_n,
> + core_dpll_clkoutdiv_m2);
> + pr_debug("switch_latency = %d, sys_clk_rate = %d,
> cycles = %d\n",
> + switch_latency,
> sys_clk_rate, c);
>
> pr_debug("clock: changing CORE DPLL rate from %lu to
> %lu\n", clk->rate,
> validrate);
> diff --git a/arch/arm/mach-omap2/clock34xx.h
> b/arch/arm/mach-omap2/clock34xx.h
> index 628e8de..a9f2204 100644
> --- a/arch/arm/mach-omap2/clock34xx.h
> +++ b/arch/arm/mach-omap2/clock34xx.h
> @@ -12,4 +12,6 @@ extern const struct clkops
> clkops_omap3430es2_ssi_wait;
> extern const struct clkops clkops_omap3430es2_hsotgusb_wait;
> extern const struct clkops clkops_omap3430es2_dss_usbhost_wait;
>
> +unsigned int delay_sram_val(void);
> +
> #endif
> diff --git a/arch/arm/mach-omap2/clock3xxx.c
> b/arch/arm/mach-omap2/clock3xxx.c
> index a447c4d..ce84a98 100644
> --- a/arch/arm/mach-omap2/clock3xxx.c
> +++ b/arch/arm/mach-omap2/clock3xxx.c
> @@ -38,7 +38,7 @@
> #define DPLL5_FREQ_FOR_USBHOST 120000000
>
> /* needed by omap3_core_dpll_m2_set_rate() */
> -struct clk *sdrc_ick_p, *arm_fck_p;
> +struct clk *sdrc_ick_p, *arm_fck_p, *sys_ck_p;
>
> int omap3_dpll4_set_rate(struct clk *clk, unsigned long rate)
> {
> diff --git a/arch/arm/mach-omap2/clock3xxx.h
> b/arch/arm/mach-omap2/clock3xxx.h
> index 8bbeeaf..475d0c7 100644
> --- a/arch/arm/mach-omap2/clock3xxx.h
> +++ b/arch/arm/mach-omap2/clock3xxx.h
> @@ -15,6 +15,7 @@ void omap3_clk_lock_dpll5(void);
>
> extern struct clk *sdrc_ick_p;
> extern struct clk *arm_fck_p;
> +extern struct clk *sys_ck_p;
>
> extern const struct clkops clkops_noncore_dpll_ops;
>
> diff --git a/arch/arm/mach-omap2/clock3xxx_data.c
> b/arch/arm/mach-omap2/clock3xxx_data.c
> index 57522de..280adff 100644
> --- a/arch/arm/mach-omap2/clock3xxx_data.c
> +++ b/arch/arm/mach-omap2/clock3xxx_data.c
> @@ -22,6 +22,7 @@
>
> #include <plat/control.h>
> #include <plat/clkdev_omap.h>
> +#include <plat/sram.h>
>
> #include "clock.h"
> #include "clock3xxx.h"
> @@ -57,6 +58,8 @@
> static struct clk dpll1_fck;
> static struct clk dpll2_fck;
>
> +static unsigned int delay_sram;
> +
> /* PRM CLOCKS */
>
> /* According to timer32k.c, this is a 32768Hz clock, not a
> 32000Hz clock. */
> @@ -3598,6 +3601,16 @@ int __init omap3xxx_clk_init(void)
> /* Avoid sleeping during omap3_core_dpll_m2_set_rate() */
> sdrc_ick_p = clk_get(NULL, "sdrc_ick");
> arm_fck_p = clk_get(NULL, "arm_fck");
> + sys_ck_p = clk_get(NULL, "sys_ck");
> +
> + /* Measure sram delay */
> + delay_sram = measure_sram_delay(10000);
> + pr_debug("SRAM delay: %d\n", delay_sram);
>
> return 0;
> }
> +
> +unsigned int delay_sram_val(void)
> +{
> + return delay_sram;
> +}
> diff --git a/arch/arm/mach-omap2/sram34xx.S
> b/arch/arm/mach-omap2/sram34xx.S
> index de99ba2..5a1631f 100644
> --- a/arch/arm/mach-omap2/sram34xx.S
> +++ b/arch/arm/mach-omap2/sram34xx.S
> @@ -313,3 +313,11 @@ core_m2_mask_val:
> ENTRY(omap3_sram_configure_core_dpll_sz)
> .word . - omap3_sram_configure_core_dpll
>
> +ENTRY(__sram_wait_delay)
> + subs r0, r0, #1 @ loop till counter = 0
> + bne __sram_wait_delay
> +
> + mov pc, lr
> +
> +ENTRY(__sram_wait_delay_sz)
> + .word . - __sram_wait_delay
> diff --git a/arch/arm/plat-omap/include/plat/sram.h
> b/arch/arm/plat-omap/include/plat/sram.h
> index 16a1b45..dd294a8 100644
> --- a/arch/arm/plat-omap/include/plat/sram.h
> +++ b/arch/arm/plat-omap/include/plat/sram.h
> @@ -69,6 +69,10 @@ extern u32 omap3_sram_configure_core_dpll(
> u32 sdrc_actim_ctrl_b_1, u32 sdrc_mr_1);
> extern unsigned long omap3_sram_configure_core_dpll_sz;
>
> +extern unsigned int measure_sram_delay(unsigned int);
> +extern void __sram_wait_delay(unsigned int);
> +extern unsigned long __sram_wait_delay_sz;
> +
> #ifdef CONFIG_PM
> extern void omap_push_sram_idle(void);
> #else
> diff --git a/arch/arm/plat-omap/sram.c b/arch/arm/plat-omap/sram.c
> index 51f4dfb..a83d422 100644
> --- a/arch/arm/plat-omap/sram.c
> +++ b/arch/arm/plat-omap/sram.c
> @@ -30,6 +30,9 @@
> #include <plat/cpu.h>
> #include <plat/vram.h>
>
> +#include <linux/clk.h>
> +#include <plat/dmtimer.h>
> +#include <plat/io.h>
> #include <plat/control.h>
>
> #if defined(CONFIG_ARCH_OMAP2) || defined(CONFIG_ARCH_OMAP3)
> @@ -437,11 +440,59 @@ static inline int omap34xx_sram_init(void)
> }
> #endif
>
> +#ifdef CONFIG_ARCH_OMAP3
> +void (*_omap3_sram_delay)(unsigned int);
> +unsigned int measure_sram_delay(unsigned int loop)
> +{
> + static struct omap_dm_timer *gpt;
> + unsigned long flags, diff = 0, gt_rate, mpurate;
> + unsigned int delay_sram, error_gain;
> + unsigned int start = 0, end = 0;
> +
> + omap_dm_timer_init();
> + gpt = omap_dm_timer_request();
> + if (!gpt) {

Request timer API returns NULL on failure.
Use BUG_ON(gpt == NULL);

> + pr_err("Could not get the gptimer\n");
> + return -1;

If timer is not available, can we use fixed delay instead
returning error.

> + }
> +
> + omap_dm_timer_set_source(gpt, OMAP_TIMER_SRC_SYS_CLK);
> +
> + gt_rate = clk_get_rate(omap_dm_timer_get_fclk(gpt));
> + omap_dm_timer_set_load_start(gpt, 0, 0);
> +
> + local_irq_save(flags);
> + start = omap_dm_timer_read_counter(gpt);
> + _omap3_sram_delay(loop);
> + end = omap_dm_timer_read_counter(gpt);
> + diff = end - start;
> + local_irq_restore(flags);
> +
> + omap_dm_timer_stop(gpt);
> + omap_dm_timer_free(gpt);
> +
> + mpurate = clk_get_rate(clk_get(NULL, "arm_fck"));
> +
> + /* calculate the sram delay */
> + delay_sram = (((mpurate / gt_rate) * diff) / (loop * 2));
> +
> + error_gain = mpurate / gt_rate;
> + delay_sram = delay_sram + error_gain;
> +
> + return delay_sram;
> +}
> +#endif
> +
> int __init omap_sram_init(void)
> {
> omap_detect_sram();
> omap_map_sram();
>
> +#ifdef CONFIG_ARCH_OMAP3
> + _omap3_sram_delay = omap_sram_push(__sram_wait_delay,
> + __sram_wait_delay_sz);
> +#endif
> +
> if (!(cpu_class_is_omap2()))
> omap1_sram_init();
> else if (cpu_is_omap242x())
> --
> 1.5.6.3
>
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