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Subject[PATCH 4/8] ARM: at91: PM: add cpu idle support for sama7g5
Date
Add CPU idle support for SAMA7G5. Support will make use of PMC_CPU_RATIO
register to divide the CPU clock by 16 before switching it to idle and
use automatic self-refresh option of DDR controller.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
---
arch/arm/mach-at91/pm.c | 27 ++++++++++++++++++++++++++-
include/linux/clk/at91_pmc.h | 4 ++++
include/soc/at91/sama7-ddr.h | 1 +
3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
index dd6f4ce3f766..0fd609e26615 100644
--- a/arch/arm/mach-at91/pm.c
+++ b/arch/arm/mach-at91/pm.c
@@ -605,6 +605,30 @@ static void at91sam9_sdram_standby(void)
at91_ramc_write(1, AT91_SDRAMC_LPR, saved_lpr1);
}

+static void sama7g5_standby(void)
+{
+ int pwrtmg, ratio;
+
+ pwrtmg = readl(soc_pm.data.ramc[0] + UDDRC_PWRCTL);
+ ratio = readl(soc_pm.data.pmc + AT91_PMC_RATIO);
+
+ /*
+ * Place RAM into self-refresh after a maximum idle clocks. The maximum
+ * idle clocks is configured by bootloader in
+ * UDDRC_PWRMGT.SELFREF_TO_X32.
+ */
+ writel(pwrtmg | UDDRC_PWRCTL_SELFREF_EN,
+ soc_pm.data.ramc[0] + UDDRC_PWRCTL);
+ /* Divide CPU clock by 16. */
+ writel(ratio & ~AT91_PMC_RATIO_RATIO, soc_pm.data.pmc + AT91_PMC_RATIO);
+
+ cpu_do_idle();
+
+ /* Restore previous configuration. */
+ writel(ratio, soc_pm.data.pmc + AT91_PMC_RATIO);
+ writel(pwrtmg, soc_pm.data.ramc[0] + UDDRC_PWRCTL);
+}
+
struct ramc_info {
void (*idle)(void);
unsigned int memctrl;
@@ -615,6 +639,7 @@ static const struct ramc_info ramc_infos[] __initconst = {
{ .idle = at91sam9_sdram_standby, .memctrl = AT91_MEMCTRL_SDRAMC},
{ .idle = at91_ddr_standby, .memctrl = AT91_MEMCTRL_DDRSDR},
{ .idle = sama5d3_ddr_standby, .memctrl = AT91_MEMCTRL_DDRSDR},
+ { .idle = sama7g5_standby, },
};

static const struct of_device_id ramc_ids[] __initconst = {
@@ -622,7 +647,7 @@ static const struct of_device_id ramc_ids[] __initconst = {
{ .compatible = "atmel,at91sam9260-sdramc", .data = &ramc_infos[1] },
{ .compatible = "atmel,at91sam9g45-ddramc", .data = &ramc_infos[2] },
{ .compatible = "atmel,sama5d3-ddramc", .data = &ramc_infos[3] },
- { .compatible = "microchip,sama7g5-uddrc", },
+ { .compatible = "microchip,sama7g5-uddrc", .data = &ramc_infos[4], },
{ /*sentinel*/ }
};

diff --git a/include/linux/clk/at91_pmc.h b/include/linux/clk/at91_pmc.h
index ccb3f034bfa9..3484309b59bf 100644
--- a/include/linux/clk/at91_pmc.h
+++ b/include/linux/clk/at91_pmc.h
@@ -78,6 +78,10 @@
#define AT91_PMC_MAINRDY (1 << 16) /* Main Clock Ready */

#define AT91_CKGR_PLLAR 0x28 /* PLL A Register */
+
+#define AT91_PMC_RATIO 0x2c /* Processor clock ratio register [SAMA7G5 only] */
+#define AT91_PMC_RATIO_RATIO (0xf) /* CPU clock ratio. */
+
#define AT91_CKGR_PLLBR 0x2c /* PLL B Register */
#define AT91_PMC_DIV (0xff << 0) /* Divider */
#define AT91_PMC_PLLCOUNT (0x3f << 8) /* PLL Counter */
diff --git a/include/soc/at91/sama7-ddr.h b/include/soc/at91/sama7-ddr.h
index fee1b11bddca..9e17247474fa 100644
--- a/include/soc/at91/sama7-ddr.h
+++ b/include/soc/at91/sama7-ddr.h
@@ -53,6 +53,7 @@
#define UDDRC_STAT_OPMODE_MSK (0x7 << 0) /* Operating mode mask */

#define UDDRC_PWRCTL (0x30) /* UDDRC Low Power Control Register */
+#define UDDRC_PWRCTL_SELFREF_EN (1 << 0) /* Automatic self-refresh */
#define UDDRC_PWRCTL_SELFREF_SW (1 << 5) /* Software self-refresh */

#define UDDRC_DFIMISC (0x1B0) /* UDDRC DFI Miscellaneous Control Register */
--
2.32.0
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