openwrt/target/linux/brcm2708/patches-4.19/950-0614-clk-bcm2835-Add-support-for-setting-leaf-clock-rates.patch
Álvaro Fernández Rojas 4295485719 brcm2708: add linux 4.19 support
Boot tested on Raspberry Pi B+ (BCM2708) and Raspberry Pi 2 (BCM2709)

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
2019-07-14 12:44:14 +02:00

54 lines
1.8 KiB
Diff

From ace78bef08082eb8971b87b28525926cd86b68c1 Mon Sep 17 00:00:00 2001
From: Eric Anholt <eric@anholt.net>
Date: Thu, 2 May 2019 15:11:05 -0700
Subject: [PATCH 614/703] clk: bcm2835: Add support for setting leaf clock
rates while running.
As long as you wait for !BUSY, you can do glitch-free updates of clock
rate while the clock is running.
Signed-off-by: Eric Anholt <eric@anholt.net>
---
drivers/clk/bcm/clk-bcm2835.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -1097,15 +1097,19 @@ static int bcm2835_clock_set_rate(struct
spin_lock(&cprman->regs_lock);
- /*
- * Setting up frac support
- *
- * In principle it is recommended to stop/start the clock first,
- * but as we set CLK_SET_RATE_GATE during registration of the
- * clock this requirement should be take care of by the
- * clk-framework.
+ ctl = cprman_read(cprman, data->ctl_reg);
+
+ /* If the clock is running, we have to pause clock generation while
+ * updating the control and div regs. This is glitchless (no clock
+ * signals generated faster than the rate) but each reg access is two
+ * OSC cycles so the clock will slow down for a moment.
*/
- ctl = cprman_read(cprman, data->ctl_reg) & ~CM_FRAC;
+ if (ctl & CM_ENABLE) {
+ cprman_write(cprman, data->ctl_reg, ctl & ~CM_ENABLE);
+ bcm2835_clock_wait_busy(clock);
+ }
+
+ ctl &= ~CM_FRAC;
ctl |= (div & CM_DIV_FRAC_MASK) ? CM_FRAC : 0;
cprman_write(cprman, data->ctl_reg, ctl);
@@ -1475,7 +1479,7 @@ static struct clk_hw *bcm2835_register_c
init.ops = &bcm2835_vpu_clock_clk_ops;
} else {
init.ops = &bcm2835_clock_clk_ops;
- init.flags |= CLK_SET_RATE_GATE | CLK_SET_PARENT_GATE;
+ init.flags |= CLK_SET_PARENT_GATE;
/* If the clock wasn't actually enabled at boot, it's not
* critical.