Hi Steve,

On Wed, Mar 08, 2023 at 11:08:34AM -0800, Steve Clevenger wrote:

[...]

I'm familiar with this interface. The reason I chose not to use it is this solution is configured at compile time. The writeq_relaxed (used by etm4x_relaxed_write64) and readq_relaxed (used by etm4x_relaxed_read64) otherwise default to 64-bit access. I was uncertain how a compile time change would go over with the maintainers. Correct me, but compile time configurations in the kernel seem to be related to ARM64 erratum, versus manufacturer specific?

My take (based on limited knowledge) of the changes necessary to support a compile time decision seemed to exceed the changes compared with the implementation I submitted upstream. If this becomes a sticking point, let me know.

I am suggesting something like below:

#include <linux/io-64-nonatomic-hi-lo.h>

static inline u64 etm4x_relaxed_read64(struct csdev_access *csa, unsigned int offset) { if (csa->io_mem) { if (csa->no_quad_mmio) return hi_lo_readq_relaxed(csa->base + offset); else return readq_relaxed(csa->base + offset); } else { return read_etm4x_sysreg_offset(offset, true); } }

I'm not saying to play magic on {writeq|readq}_relaxed(), would it be fine to directly call hi_lo_readq_relaxed()?

Thanks, Leo