On Wed, 10 Feb 2021 14:15:46 +0100
Nicolas Saenz Julienne [off-list ref] wrote:

[ Add Robin, Catalin and Florian in case they want to chime in ]

Hi Juerg, thanks for the report!

On Wed, 2021-02-10 at 11:48 +0100, Juerg Haefliger wrote:

quoted

Trying to dump the BCM2711 registers kills the kernel:

# cat /sys/kernel/debug/regmap/dummy-avs-monitor\@fd5d2000/range
0-efc
# cat /sys/kernel/debug/regmap/dummy-avs-monitor\@fd5d2000/registers 

[   62.857661] SError Interrupt on CPU1, code 0xbf000002 -- SError  

So ESR's IDS (bit 24) is set, which means it's an 'Implementation Defined
SError,' hence IIUC the rest of the error code is meaningless to anyone outside
of Broadcom/RPi.

The regmap is created through the following syscon device:

	avs_monitor: avs-monitor@7d5d2000 {
		compatible = "brcm,bcm2711-avs-monitor",
			     "syscon", "simple-mfd";
		reg = <0x7d5d2000 0xf00>;

		thermal: thermal {
			compatible = "brcm,bcm2711-thermal";
			#thermal-sensor-cells = <0>;
		};
	};

I've done some tests with devmem, and the whole <0x7d5d2000 0xf00> range is
full of addresses that trigger this same error. Also note that as per Florian's
comments[1]: "AVS_RO_REGISTERS_0: 0x7d5d2200 - 0x7d5d22e3." But from what I can
tell, at least 0x7d5d22b0 seems to be faulty too.

Any ideas/comments? My guess is that those addresses are marked somehow as
secure, and only for VC4 to access (VC4 is RPi4's co-processor). Ultimately,
the solution is to narrow the register range exposed by avs-monitor to whatever
bcm2711-thermal needs (which is ATM a single 32bit register).

Yeah, that's what I tried but wasn't sure if that's the correct approach or
if there was something wrong with the DTB (which I know virtually nothing
about).

With [1] I get seemingly the correct behavior:

# cat /sys/kernel/debug/regmap/dummy-avs-monitor\@fd5d2200/range 
0-0
# cat /sys/kernel/debug/regmap/dummy-avs-monitor\@fd5d2200/registers 
0: 000106fa
# cat /sys/class/thermal/thermal_zone0/temp 
39433

On a different note, how did you come up with that address range in the DTB?
Is that public information?

...Juerg


[1]

diff --git a/arch/arm/boot/dts/bcm2711.dtsi b/arch/arm/boot/dts/bcm2711.dtsi
index 4847dd305317..a7059967aab1 100644
--- a/arch/arm/boot/dts/bcm2711.dtsi
+++ b/arch/arm/boot/dts/bcm2711.dtsi

@@ -65,10 +65,10 @@ gicv2: interrupt-controller@40041000 {
                                                 IRQ_TYPE_LEVEL_HIGH)>;
                };
 
-               avs_monitor: avs-monitor@7d5d2000 {
+               avs_monitor: avs-monitor@7d5d2200 {
                        compatible = "brcm,bcm2711-avs-monitor",
                                     "syscon", "simple-mfd";
-                       reg = <0x7d5d2000 0xf00>;
+                       reg = <0x7d5d2200 0x4>;
 
                        thermal: thermal {
                                compatible = "brcm,bcm2711-thermal";

diff --git a/drivers/thermal/broadcom/bcm2711_thermal.c b/drivers/thermal/broadcom/bcm2711_thermal.c
index 67c2a737bc9d..3b5a84402b89 100644
--- a/drivers/thermal/broadcom/bcm2711_thermal.c
+++ b/drivers/thermal/broadcom/bcm2711_thermal.c

@@ -22,7 +22,7 @@
 
 #include "../thermal_hwmon.h"
 
-#define AVS_RO_TEMP_STATUS             0x200
+#define AVS_RO_TEMP_STATUS             0x0 /* address 0x7d5d2200 */
 #define AVS_RO_TEMP_STATUS_VALID_MSK   (BIT(16) | BIT(10))
 #define AVS_RO_TEMP_STATUS_DATA_MSK    GENMASK(9, 0)

Regards,
Nicolas

[1] https://lore.kernel.org/linux-pm/82125042-684a-b4e2-fbaa-45a393b2ce5e@gmx.net/ (local)

quoted

[   62.857671] CPU: 1 PID: 478 Comm: cat Not tainted 5.11.0-rc7 #4
[   62.857674] Hardware name: Raspberry Pi 4 Model B Rev 1.2 (DT)
[   62.857676] pstate: 20000085 (nzCv daIf -PAN -UAO -TCO BTYPE=--)
[   62.857679] pc : regmap_mmio_read32le+0x1c/0x34
[   62.857681] lr : regmap_mmio_read+0x50/0x80
[   62.857682] sp : ffff8000105c3c00
[   62.857685] x29: ffff8000105c3c00 x28: 0000000000000014 
[   62.857694] x27: 0000000000000014 x26: ffffd2ea1c2060b0 
[   62.857699] x25: ffff4e34408ecc00 x24: 0000000000000efc 
[   62.857704] x23: ffff8000105c3e20 x22: ffff8000105c3d3c 
[   62.857710] x21: ffff8000105c3d3c x20: 0000000000000014 
[   62.857715] x19: ffff4e344037a900 x18: 0000000000000020 
[   62.857720] x17: 0000000000000000 x16: 0000000000000000 
[   62.857725] x15: ffff4e3447ac40f0 x14: 0000000000000003 
[   62.857730] x13: ffff4e34422c0000 x12: ffff4e34422a0046 
[   62.857735] x11: ffffd2ea1c8765e0 x10: 0000000000000000 
[   62.857741] x9 : ffffd2ea1b9495a0 x8 : ffff4e34429ef980 
[   62.857746] x7 : 000000000000000f x6 : ffff4e34422a004b 
[   62.857751] x5 : 00000000fffffff9 x4 : 0000000000000000 
[   62.857757] x3 : ffffd2ea1b949550 x2 : ffffd2ea1b949330 
[   62.857761] x1 : 0000000000000014 x0 : 0000000000000000 
[   62.857767] Kernel panic - not syncing: Asynchronous SError Interrupt
[   62.857770] CPU: 1 PID: 478 Comm: cat Not tainted 5.11.0-rc7 #4
[   62.857773] Hardware name: Raspberry Pi 4 Model B Rev 1.2 (DT)
[   62.857775] Call trace:
[   62.857777]  dump_backtrace+0x0/0x1e0
[   62.857778]  show_stack+0x24/0x70
[   62.857780]  dump_stack+0xd0/0x12c
[   62.857782]  panic+0x168/0x370
[   62.857783]  nmi_panic+0x98/0xa0
[   62.857786]  arm64_serror_panic+0x8c/0x98
[   62.857787]  do_serror+0x3c/0x6c
[   62.857789]  el1_error+0x78/0xf0
[   62.857791]  regmap_mmio_read32le+0x1c/0x34
[   62.857793]  _regmap_bus_reg_read+0x24/0x30
[   62.857795]  _regmap_read+0x6c/0x17c
[   62.857797]  regmap_read+0x58/0x84
[   62.857799]  regmap_read_debugfs+0x138/0x3f4
[   62.857801]  regmap_map_read_file+0x34/0x40
[   62.857803]  full_proxy_read+0x6c/0xc0
[   62.857805]  vfs_read+0xb8/0x1e4
[   62.857807]  ksys_read+0x78/0x10c
[   62.857809]  __arm64_sys_read+0x28/0x34
[   62.857811]  el0_svc_common.constprop.0+0x7c/0x194
[   62.857813]  do_el0_svc+0x30/0x9c
[   62.857814]  el0_svc+0x20/0x30
[   62.857816]  el0_sync_handler+0x1a4/0x1b0
[   62.857818]  el0_sync+0x174/0x180
[   62.857842] SMP: stopping secondary CPUs
[   62.857845] Kernel Offset: 0x52ea0b080000 from 0xffff800010000000
[   62.857847] PHYS_OFFSET: 0xffffb1cc00000000
[   62.857849] CPU features: 0x00240022,61806000
[   62.857851] Memory Limit: none

Sprinkling printks around regmap_read [1] shows that reading from 0x14 (20)
seems to cause the issue:


[   40.456230] map=ffff020a069c9c00, from=0, to=3836, count=131072
[   40.462520] map=ffff020a069c9c00, i=0
[   40.466319] ret=0, val=0
[   40.468922] map=ffff020a069c9c00, i=4
[   40.472684] ret=0, val=0
[   40.475292] map=ffff020a069c9c00, i=8
[   40.479048] ret=0, val=0
[   40.481649] map=ffff020a069c9c00, i=12
[   40.485492] ret=0, val=0
[   40.488080] map=ffff020a069c9c00, i=16
[   40.491922] ret=0, val=0
[   40.494523] map=ffff020a069c9c00, i=20
[   40.498497] SError Interrupt on CPU0, code 0xbf000002 -- SError
[   40.498499] CPU: 0 PID: 486 Comm: cat Not tainted 5.11.0-rc7+ #8
[   40.498501] Hardware name: Raspberry Pi 4 Model B Rev 1.2 (DT)


...Juerg

[1]

diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index ff2ee87987c7..9465f5a2f3b8 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c

@@ -229,6 +229,7 @@ static ssize_t regmap_read_debugfs(struct regmap *map, unsigned int from,

        if (count > (PAGE_SIZE << (MAX_ORDER - 1)))
                count = PAGE_SIZE << (MAX_ORDER - 1);
 

+       printk("map=%px, from=%d, to=%d, count=%ld\n", map, from, to, count);
        buf = kmalloc(count, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

@@ -253,7 +254,9 @@ static ssize_t regmap_read_debugfs(struct regmap *map, unsigned int from,

                        buf_pos += map->debugfs_reg_len + 2;
 

                        /* Format the value, write all X if we can't read */
+                       printk("map=%px, i=%d\n", map, i);
                        ret = regmap_read(map, i, &val);
+                       printk("ret=%ld, val=%x\n", ret, val);
                        if (ret == 0)
                                snprintf(buf + buf_pos, count - buf_pos,
                                         "%.*x", map->debugfs_val_len, val);