6.17: apply dmacoherent patch for arm64

[nicholasaiello]

Apply DMA patch and other improvements from raspberrypi#7072

[Copilot]

Pull Request Overview

This PR applies a DMA coherent patch specifically for ARM64 architecture to address memory coherency issues in the TTM (Translation Table Manager) module. The changes ensure proper DMA coherent memory mapping on ARM64 systems while simplifying buffer mapping logic.

• Modified ttm_prot_from_caching() to use pgprot_dmacoherent() for cached mappings on ARM64
• Simplified ttm_bo_kmap_ttm() by removing single-page optimization logic
• Removed unused variable declarations in the buffer mapping function

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
drivers/gpu/drm/ttm/ttm_module.c	Added ARM64-specific DMA coherent protection for cached mappings
drivers/gpu/drm/ttm/ttm_bo_util.c	Simplified buffer mapping by removing single-page optimization and unused variables

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[Copilot]

The ARM64-specific code path bypasses the fallback return tmp statement. Consider restructuring to avoid unreachable code or add a comment explaining why the general case still applies to other architectures.

Suggested change

	if (caching == ttm_cached)
	{
	#ifdef CONFIG_ARM64
	return pgprot_dmacoherent(tmp);
	#endif
	return tmp;
	}
	#ifdef CONFIG_ARM64
	if (caching == ttm_cached)
	return pgprot_dmacoherent(tmp);
	#else
	if (caching == ttm_cached)
	return tmp;
	#endif

[Copilot]

The opening brace appears to be orphaned after removing the conditional logic. This should likely be removed or the control flow restructured to maintain proper code organization.