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/* Copyright 2024-2025 Joshua Bakita
* Implementation of Kernel-specific function implementations
*/
#include "nvdebug_linux.h"
#include <asm/io.h> // For read[l,q] and write[l,q]
#include <linux/pm_runtime.h> // For pm_runtime_[enabled,get,put]()
u32 nvdebug_readl(struct nvdebug_state *s, u32 r) {
u32 ret;
// If this is an integrated ("platform") GPU, make sure that it's on first
// (pm_runtime_enabled() will return false until nvgpu is started. Once
// nvgpu is started, pm_runtime_get_sync() will attempt to resume the GPU.
// This still increments the usage counter on failure, so we undo that with
// pm_runtime_put_noidle(). We avoid pm_runtime_resume_and_get() as it was
// not added until Linux 5.9.11)
// This works to bring up the TX2, Xavier, and Orin, but not the TX1.
if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get_sync(s->dev) < 0)) {
printk(KERN_ERR "[nvdebug] nvdebug_readl: Unable to read; registers unavailable. Is GPU on?\n");
pm_runtime_put_noidle(s->dev); // No-op if !pm_runtime_enabled()
return -1;
}
ret = readl(s->regs + r);
// If an integrated GPU, allow it to suspend again (if idle)
if (s->platd)
pm_runtime_put(s->dev);
// According to open-gpu-kernel-modules, the GPU "will return 0xbad in the
// upper 3 nibbles when there is a possible issue". Further code uses the
// middle three nibbles as an error code, and ignores the bottom two.
if ((ret & 0xfff00000) == 0xbad00000) {
printk(KERN_ERR "[nvdebug] nvdebug_readl: Unable to read from register offset %#x; bad data of %#10x\n", r, ret);
// It would be best to check INTR_0_PRI_* error is pending, to verify
// that this was actually a bad read. Possible future work...
// Generally a failure here in the context of nvdebug indicates that a
// register does not exist on this platform, but one can know for sure
// by checking which NV_PPRIV_SYS_PRI_ERROR_CODE_* define the bad read
// matches.
return -1;
}
return ret;
}
// quadword (8-byte) version of nvdebug_readl()
u64 nvdebug_readq(struct nvdebug_state *s, u32 r) {
u64 ret;
// If this is an integrated ("platform") GPU, make sure that it's on first
if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get_sync(s->dev) < 0)) {
printk(KERN_ERR "[nvdebug] nvdebug_readq: Unable to read; registers unavailable. Is GPU on?\n");
pm_runtime_put_noidle(s->dev); // No-op if !pm_runtime_enabled()
return -1;
}
// readq seems to always (?) return the uppermost 32 bits as 0, so workaround with readl
ret = readl(s->regs + r);
ret |= ((u64)readl(s->regs + r + 4)) << 32;
// If an integrated GPU, allow it to suspend again (if idle)
if (s->platd)
pm_runtime_put(s->dev);
// See comment in nvdebug_readl() regarding error checking
if ((ret & 0xfff00000ull) == 0xbad00000ull) {
printk(KERN_ERR "[nvdebug] nvdebug_readq: Unable to read from register offset %#x; bad data of %#18llx\n", r, ret);
return -1;
}
return ret;
}
void nvdebug_writel(struct nvdebug_state *s, u32 r, u32 v) {
// If this is an integrated ("platform") GPU, make sure that it's on first
if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get_sync(s->dev) < 0)) {
printk(KERN_ERR "[nvdebug] nvdebug_writel: Unable to write; registers unavailable. Is GPU on?\n");
pm_runtime_put_noidle(s->dev); // No-op if !pm_runtime_enabled()
return;
}
writel_relaxed(v, s->regs + r);
wmb();
// If an integrated GPU, allow it to suspend again (if idle)
if (s->platd)
pm_runtime_put(s->dev);
}
// quadword (8-byte) version of nvdebug_writel()
// XXX: Not clear this works on all platforms
void nvdebug_writeq(struct nvdebug_state *s, u32 r, u64 v) {
// If this is an integrated ("platform") GPU, make sure that it's on first
if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get_sync(s->dev) < 0)) {
printk(KERN_ERR "[nvdebug] nvdebug_writeq: Unable to write; registers unavailable. Is GPU on?\n");
pm_runtime_put_noidle(s->dev); // No-op if !pm_runtime_enabled()
return;
}
writeq_relaxed(v, s->regs + r);
wmb();
// If an integrated GPU, allow it to suspend again (if idle)
if (s->platd)
pm_runtime_put(s->dev);
}
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