[OpenOCD-commit] Main OpenOCD repository branch, master, updated. v0.12.0-rc1-51-gee87f2b4a

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- Log -----------------------------------------------------------------
commit ee87f2b4a9cac084903087aed6ff8e3a691c674b
Author: Jonathan Bell <jon...@ra...>
Date:   Thu Oct 13 10:38:53 2022 +0100

    jtag/drivers: bcm2835gpio: implement memory barriers when bitbashing
    
    This GPIO driver is common to SoCs that have in-order ARM cores
    (BCM2835) as well as superscalar (BCM2836-7) and speculative
    out-of-order cores (BCM2711).
    
    For BCM2837 and BCM2711, the processor can dual-issue stores and
    is free to merge writes to peripheral memory for pages mapped
    MT_NORMAL_NC, which is the default provided by /dev/[gpio]mem.
    
    This can cause glitches (or missing edges) on GPIO pins when
    toggled with no delay, as pipelined writes to the same address
    can get arbitrarily squelched.
    
    To prevent this happening, make sure the preceding write ops are
    flushed outside the shareable domain by using a memory barrier.
    
    Signed-off-by: Jonathan Bell <jon...@ra...>
    Change-Id: I8805cc0911667bcb9b7f4ca340d7f4f1cb25d096
    Reviewed-on: https://review.openocd.org/c/openocd/+/7258
    Tested-by: jenkins
    Reviewed-by: Antonio Borneo <bor...@gm...>

diff --git a/src/jtag/drivers/bcm2835gpio.c b/src/jtag/drivers/bcm2835gpio.c
index bd44fca07..5aa1a99e4 100644
--- a/src/jtag/drivers/bcm2835gpio.c
+++ b/src/jtag/drivers/bcm2835gpio.c
@@ -57,6 +57,15 @@ static struct initial_gpio_state {
 } initial_gpio_state[ADAPTER_GPIO_IDX_NUM];
 static uint32_t initial_drive_strength_etc;
 
+static inline void bcm2835_gpio_synchronize(void)
+{
+	/* Ensure that previous writes to GPIO registers are flushed out of
+	 * the inner shareable domain to prevent pipelined writes to the
+	 * same address being merged.
+	 */
+	__sync_synchronize();
+}
+
 static bool is_gpio_config_valid(enum adapter_gpio_config_index idx)
 {
 	/* Only chip 0 is supported, accept unset value (-1) too */
@@ -96,6 +105,7 @@ static void set_gpio_value(const struct adapter_gpio_config *gpio_config, int va
 		}
 		break;
 	}
+	bcm2835_gpio_synchronize();
 }
 
 static void restore_gpio(enum adapter_gpio_config_index idx)
@@ -109,6 +119,7 @@ static void restore_gpio(enum adapter_gpio_config_index idx)
 				GPIO_CLR = 1 << adapter_gpio_config[idx].gpio_num;
 		}
 	}
+	bcm2835_gpio_synchronize();
 }
 
 static void initialize_gpio(enum adapter_gpio_config_index idx)
@@ -143,6 +154,7 @@ static void initialize_gpio(enum adapter_gpio_config_index idx)
 	/* Direction for non push-pull is already set by set_gpio_value() */
 	if (adapter_gpio_config[idx].drive == ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL)
 		OUT_GPIO(adapter_gpio_config[idx].gpio_num);
+	bcm2835_gpio_synchronize();
 }
 
 static bb_value_t bcm2835gpio_read(void)
@@ -164,6 +176,7 @@ static int bcm2835gpio_write(int tck, int tms, int tdi)
 
 	GPIO_SET = set;
 	GPIO_CLR = clear;
+	bcm2835_gpio_synchronize();
 
 	for (unsigned int i = 0; i < jtag_delay; i++)
 		asm volatile ("");
@@ -184,6 +197,7 @@ static int bcm2835gpio_swd_write_fast(int swclk, int swdio)
 
 	GPIO_SET = set;
 	GPIO_CLR = clear;
+	bcm2835_gpio_synchronize();
 
 	for (unsigned int i = 0; i < jtag_delay; i++)
 		asm volatile ("");
@@ -234,6 +248,7 @@ static void bcm2835_swdio_drive(bool is_output)
 		if (is_gpio_config_valid(ADAPTER_GPIO_IDX_SWDIO_DIR))
 			set_gpio_value(&adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO_DIR], 0);
 	}
+	bcm2835_gpio_synchronize();
 }
 
 static int bcm2835_swdio_read(void)

-----------------------------------------------------------------------

Summary of changes:
 src/jtag/drivers/bcm2835gpio.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)


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