Add api to calculate and set the clock for SPI channels
Signed-off-by: James Miller jamesmiller@chromium.org Signed-off-by: Simon Glass sjg@chromium.org Signed-off-by: Rajeshwari Shinde rajeshwari.s@samsung.com Signed-off-by: Hatim Ali hatim.rv@samsung.com Acked-by: Simon Glass sjg@chromium.org --- Changes since v4: Added Signed-off-by of James Miller Changes since v5: Incorporated review comments by Minkyu Kang Changes since v6: Based on the review by Minkyu Kang, moved the include periph.h define to clock.c file Changes since v7: Rebased on u-boot-samsung.git Added Acked-by Simon Glass
diff --git a/arch/arm/cpu/armv7/exynos/clock.c b/arch/arm/cpu/armv7/exynos/clock.c index a042423..ec14e96 100644 --- a/arch/arm/cpu/armv7/exynos/clock.c +++ b/arch/arm/cpu/armv7/exynos/clock.c @@ -25,6 +25,7 @@ #include <asm/io.h> #include <asm/arch/clock.h> #include <asm/arch/clk.h> +#include <asm/arch/periph.h>
/* exynos: return pll clock frequency */ static int exynos_get_pll_clk(int pllreg, unsigned int r, unsigned int k) @@ -706,6 +707,122 @@ static unsigned long exynos5_get_i2c_clk(void) return aclk_66; }
+/** + * Linearly searches for the most accurate main and fine stage clock scalars + * (divisors) for a specified target frequency and scalar bit sizes by checking + * all multiples of main_scalar_bits values. Will always return scalars up to or + * slower than target. + * + * @param main_scalar_bits Number of main scalar bits, must be > 0 and < 32 + * @param fine_scalar_bits Number of fine scalar bits, must be > 0 and < 32 + * @param input_freq Clock frequency to be scaled in Hz + * @param target_freq Desired clock frequency in Hz + * @param best_fine_scalar Pointer to store the fine stage divisor + * + * @return best_main_scalar Main scalar for desired frequency or -1 if none + * found + */ +static int clock_calc_best_scalar(unsigned int main_scaler_bits, + unsigned int fine_scalar_bits, unsigned int input_rate, + unsigned int target_rate, unsigned int *best_fine_scalar) +{ + int i; + int best_main_scalar = -1; + unsigned int best_error = target_rate; + const unsigned int cap = (1 << fine_scalar_bits) - 1; + const unsigned int loops = 1 << main_scaler_bits; + + debug("Input Rate is %u, Target is %u, Cap is %u\n", input_rate, + target_rate, cap); + + assert(best_fine_scalar != NULL); + assert(main_scaler_bits <= fine_scalar_bits); + + *best_fine_scalar = 1; + + if (input_rate == 0 || target_rate == 0) + return -1; + + if (target_rate >= input_rate) + return 1; + + for (i = 1; i <= loops; i++) { + const unsigned int effective_div = max(min(input_rate / i / + target_rate, cap), 1); + const unsigned int effective_rate = input_rate / i / + effective_div; + const int error = target_rate - effective_rate; + + debug("%d|effdiv:%u, effrate:%u, error:%d\n", i, effective_div, + effective_rate, error); + + if (error >= 0 && error <= best_error) { + best_error = error; + best_main_scalar = i; + *best_fine_scalar = effective_div; + } + } + + return best_main_scalar; +} + +static int exynos5_set_spi_clk(enum periph_id periph_id, + unsigned int rate) +{ + struct exynos5_clock *clk = + (struct exynos5_clock *)samsung_get_base_clock(); + int main; + unsigned int fine; + unsigned shift, pre_shift; + unsigned mask = 0xff; + u32 *reg; + + main = clock_calc_best_scalar(4, 8, 400000000, rate, &fine); + if (main < 0) { + debug("%s: Cannot set clock rate for periph %d", + __func__, periph_id); + return -1; + } + main = main - 1; + fine = fine - 1; + + switch (periph_id) { + case PERIPH_ID_SPI0: + reg = &clk->div_peric1; + shift = 0; + pre_shift = 8; + break; + case PERIPH_ID_SPI1: + reg = &clk->div_peric1; + shift = 16; + pre_shift = 24; + break; + case PERIPH_ID_SPI2: + reg = &clk->div_peric2; + shift = 0; + pre_shift = 8; + break; + case PERIPH_ID_SPI3: + reg = &clk->sclk_div_isp; + shift = 0; + pre_shift = 4; + break; + case PERIPH_ID_SPI4: + reg = &clk->sclk_div_isp; + shift = 12; + pre_shift = 16; + break; + default: + debug("%s: Unsupported peripheral ID %d\n", __func__, + periph_id); + return -1; + } + clrsetbits_le32(reg, mask << shift, (main & mask) << shift); + clrsetbits_le32(reg, mask << pre_shift, (fine & mask) << pre_shift); + + return 0; +} + unsigned long get_pll_clk(int pllreg) { if (cpu_is_exynos5()) @@ -777,3 +894,11 @@ void set_mipi_clk(void) if (cpu_is_exynos4()) exynos4_set_mipi_clk(); } + +int set_spi_clk(int periph_id, unsigned int rate) +{ + if (cpu_is_exynos5()) + return exynos5_set_spi_clk(periph_id, rate); + else + return 0; +} diff --git a/arch/arm/include/asm/arch-exynos/clk.h b/arch/arm/include/asm/arch-exynos/clk.h index 5529025..c18ddaa 100644 --- a/arch/arm/include/asm/arch-exynos/clk.h +++ b/arch/arm/include/asm/arch-exynos/clk.h @@ -39,4 +39,5 @@ unsigned long get_lcd_clk(void); void set_lcd_clk(void); void set_mipi_clk(void);
+int set_spi_clk(int periph_id, unsigned int rate); #endif