Claude review: drm/xe/xe_hw_error: Add support for PVC SoC errors

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Bug: Correctable errors blindly clear all register bits**

```c
if (hw_err == HARDWARE_ERROR_CORRECTABLE) {
    xe_mmio_write32(mmio, SOC_GLOBAL_ERR_STAT_REG(master, hw_err), REG_GENMASK(31, 0));
    xe_mmio_write32(mmio, SOC_LOCAL_ERR_STAT_REG(master, hw_err), REG_GENMASK(31, 0));
    xe_mmio_write32(mmio, SOC_GLOBAL_ERR_STAT_REG(slave, hw_err), REG_GENMASK(31, 0));
    xe_mmio_write32(mmio, SOC_LOCAL_ERR_STAT_REG(slave, hw_err), REG_GENMASK(31, 0));
    goto unmask_gsysevtctl;
}
```

For correctable SoC errors, the registers are cleared without being read first. This means: (1) no counter is incremented for correctable SoC errors (the counter value reported via netlink will always be 0), and (2) no diagnostic log messages are emitted. This seems like a significant gap — the netlink interface claims to report soc-internal correctable errors but the value will never change.

**Concern: `log_soc_error` uses `strcmp` against string literal**

```c
if (strcmp(name, "Undefined")) {
    ...
    atomic_inc(&info[index].counter);
}
```

Using string comparison to decide whether to count an error is fragile. A sentinel value (NULL) or a bitmask approach would be more robust. If someone changes the "Undefined" string, the filter silently breaks.

**Concern: GSYSEVTCTL unmask value is magic number**

```c
xe_mmio_write32(mmio, SOC_GSYSEVTCTL_REG(master, slave, i),
                (HARDWARE_ERROR_MAX << 1) + 1);
```

`(HARDWARE_ERROR_MAX << 1) + 1` = `(3 << 1) + 1` = `7` = `0b111`. This magic number represents "enable all three error types." A define like `SOC_GSYSEVTCTL_UNMASK_ALL` would improve readability.

**Minor: Missing newline in drm_warn/drm_err format strings**

```c
drm_warn(&xe->drm, "%s SOC %s detected", name, severity_str);
drm_err_ratelimited(&xe->drm, "%s SOC %s detected", name, severity_str);
```

These format strings lack a trailing `\n`. While `drm_warn`/`drm_err` may add one internally, it's inconsistent with all other log calls in this file which include `\n`.

**Minor: `slave` variable in `soc_hw_error_handler` is unused after initialization**

```c
u32 master, slave, regbit;
...
master = SOC_PVC_MASTER_BASE;
slave = SOC_PVC_SLAVE_BASE;
```

`slave` is only used in the `SOC_GSYSEVTCTL_REG` macro calls and in the correctable error clearing path. The variable is needed but could be `const` for clarity.

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Generated by Claude Code Patch Reviewer