[PATCH 12/21] drm/tilcdc: Allow build without __iowmb()

[Tomi Valkeinen]

On 08/04/2024 20:04, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> __iowmb() isn't available on most architectures. Make
> its use optional so that the driver can be built on
> other architectures with COMPILE_TEST=y.
> 
> Cc: Jyri Sarha <jyri.sarha at iki.fi>
> Cc: Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>   drivers/gpu/drm/tilcdc/tilcdc_regs.h | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_regs.h b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
> index f90e2dc3457c..44e4ada30fba 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_regs.h
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
> @@ -125,7 +125,9 @@ static inline void tilcdc_write64(struct drm_device *dev, u32 reg, u64 data)
>   #if defined(iowrite64) && !defined(iowrite64_is_nonatomic)
>   	iowrite64(data, addr);
>   #else
> +#ifdef __iowmb
>   	__iowmb();
> +#endif
>   	/* This compiles to strd (=64-bit write) on ARM7 */
>   	*(volatile u64 __force *)addr = __cpu_to_le64(data);
>   #endif

As the memory barrier is an important part there, would it be better to 
ifdef based on COMPILE_TEST, to make it clear why it's being done?

  Tomi