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From 9667f053b5015bfb486e16d3c88a79b961395876 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Mon, 6 Mar 2017 09:06:18 +0000
Subject: [PATCH] clk-bcm2835: Read max core clock from firmware
The VPU is responsible for managing the core clock, usually under
direction from the bcm2835-cpufreq driver but not via the clk-bcm2835
driver. Since the core frequency can change without warning, it is
safer to report the maximum clock rate to users of the core clock -
I2C, SPI and the mini UART - to err on the safe side when calculating
clock divisors.
If the DT node for the clock driver includes a reference to the
firmware node, use the firmware API to query the maximum core clock
instead of reading the divider registers.
Prior to this patch, a "100KHz" I2C bus was sometimes clocked at about
160KHz. In particular, switching to the 4.9 kernel was likely to break
SenseHAT usage on a Pi3.
Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
drivers/clk/bcm/clk-bcm2835.c | 39 ++++++++++++++++++++++++++++++++++-
1 file changed, 38 insertions(+), 1 deletion(-)
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -35,6 +35,7 @@
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <dt-bindings/clock/bcm2835.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
#define CM_PASSWORD 0x5a000000
@@ -295,6 +296,8 @@
#define SOC_BCM2711 BIT(1)
#define SOC_ALL (SOC_BCM2835 | SOC_BCM2711)
+#define VCMSG_ID_CORE_CLOCK 4
+
/*
* Names of clocks used within the driver that need to be replaced
* with an external parent's name. This array is in the order that
@@ -313,6 +316,7 @@ static const char *const cprman_parent_n
struct bcm2835_cprman {
struct device *dev;
void __iomem *regs;
+ struct rpi_firmware *fw;
spinlock_t regs_lock; /* spinlock for all clocks */
unsigned int soc;
@@ -1010,6 +1014,30 @@ static unsigned long bcm2835_clock_get_r
return bcm2835_clock_rate_from_divisor(clock, parent_rate, div);
}
+static unsigned long bcm2835_clock_get_rate_vpu(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
+ struct bcm2835_cprman *cprman = clock->cprman;
+
+ if (cprman->fw) {
+ struct {
+ u32 id;
+ u32 val;
+ } packet;
+
+ packet.id = VCMSG_ID_CORE_CLOCK;
+ packet.val = 0;
+
+ if (!rpi_firmware_property(cprman->fw,
+ RPI_FIRMWARE_GET_MAX_CLOCK_RATE,
+ &packet, sizeof(packet)))
+ return packet.val;
+ }
+
+ return bcm2835_clock_get_rate(hw, parent_rate);
+}
+
static void bcm2835_clock_wait_busy(struct bcm2835_clock *clock)
{
struct bcm2835_cprman *cprman = clock->cprman;
@@ -1298,7 +1326,7 @@ static int bcm2835_vpu_clock_is_on(struc
*/
static const struct clk_ops bcm2835_vpu_clock_clk_ops = {
.is_prepared = bcm2835_vpu_clock_is_on,
- .recalc_rate = bcm2835_clock_get_rate,
+ .recalc_rate = bcm2835_clock_get_rate_vpu,
.set_rate = bcm2835_clock_set_rate,
.determine_rate = bcm2835_clock_determine_rate,
.set_parent = bcm2835_clock_set_parent,
@@ -2236,6 +2264,7 @@ static int bcm2835_clk_probe(struct plat
const struct bcm2835_clk_desc *desc;
const size_t asize = ARRAY_SIZE(clk_desc_array);
const struct cprman_plat_data *pdata;
+ struct device_node *fw_node;
size_t i;
u32 clk_id;
int ret;
@@ -2257,6 +2286,14 @@ static int bcm2835_clk_probe(struct plat
if (IS_ERR(cprman->regs))
return PTR_ERR(cprman->regs);
+ fw_node = of_parse_phandle(dev->of_node, "firmware", 0);
+ if (fw_node) {
+ struct rpi_firmware *fw = rpi_firmware_get(NULL);
+ if (!fw)
+ return -EPROBE_DEFER;
+ cprman->fw = fw;
+ }
+
memset(bcm2835_clk_claimed, 0, sizeof(bcm2835_clk_claimed));
for (i = 0;
!of_property_read_u32_index(pdev->dev.of_node, "claim-clocks",
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