From 6113493e995480949876c74ec24ecd202004c3ae Mon Sep 17 00:00:00 2001 From: Phil Elwell 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 --- 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 @@ -36,6 +36,7 @@ #include #include #include +#include #define CM_PASSWORD 0x5a000000 @@ -296,6 +297,8 @@ #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 @@ -314,6 +317,7 @@ 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; @@ -1040,6 +1044,30 @@ static unsigned long bcm2835_clock_get_r return rate; } +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; @@ -1328,7 +1356,7 @@ 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, @@ -2304,6 +2332,7 @@ 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; @@ -2324,6 +2353,14 @@ 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",