[Intel-gfx] [PATCH 2/2] drm/i915: Add lmem_bar_size modparam

[Matthew Auld]

On 15/06/2022 06:43, priyanka.dandamudi at intel.com wrote:
> From: Priyanka Dandamudi <priyanka.dandamudi at intel.com>
> 
> lmem_bar_size is used to resize lmem bar.
> It sets to only one of the supported sizes.
> Setting this param will be in MB unit.

Maybe add some more information here for why we want to add this?

Something like:

"For testing purposes, support forcing the lmem_bar size through a new 
modparam. In CI we only have a limited number of configurations for DG2, 
but we still need to be reasonably sure we get a usable device (also 
verifying we report the correct values for things like 
probed_cpu_visible_size etc) with all the potential lmem_bar sizes that 
we might expect see in the wild."

?

> 
> Cc: Matthew Auld <matthew.auld at intel.com>
> Signed-off-by: Priyanka Dandamudi <priyanka.dandamudi at intel.com>
> ---
>   drivers/gpu/drm/i915/gt/intel_region_lmem.c |  3 +++
>   drivers/gpu/drm/i915/i915_driver.c          | 25 ++++++++++++++++++++-
>   drivers/gpu/drm/i915/i915_params.c          |  2 ++
>   drivers/gpu/drm/i915/i915_params.h          |  1 +
>   4 files changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
> index 119e53f5d9b1..d73d8b2adfa2 100644
> --- a/drivers/gpu/drm/i915/gt/intel_region_lmem.c
> +++ b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
> @@ -132,6 +132,9 @@ static struct intel_memory_region *setup_lmem(struct intel_gt *gt)
>   				  mul_u32_u32(i915->params.lmem_size, SZ_1M));
>   	}
>   
> +	if (i915->params.lmem_bar_size > 0)
> +		lmem_size = pci_resource_len(pdev, 2);

This is just a temporary hack until we have all the small-bar stuff 
landed, right? If so, maybe annotate with:

/* XXX: remove once we land small-bar uapi bits */

So we don't forget to remove this.

> +
>   	io_start = pci_resource_start(pdev, 2);
>   	io_size = min(pci_resource_len(pdev, 2), lmem_size);
>   	if (!io_size)
> diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
> index 8d33a6a31675..2f5d7a1f1a7b 100644
> --- a/drivers/gpu/drm/i915/i915_driver.c
> +++ b/drivers/gpu/drm/i915/i915_driver.c
> @@ -371,7 +371,30 @@ static void i915_resize_lmem_bar(struct drm_i915_private *i915)
>   	u32 pci_cmd;
>   	int i;
>   
> -	if (!rebar_size)
> +	if (i915->params.lmem_bar_size > 0) {
> +		u32 lmem_bar_size;
> +		u32 set_bit;
> +		u32 rebar;
> +		u32 msb;
> +		int k;
> +
> +		lmem_bar_size = i915->params.lmem_bar_size;
> +		rebar = pci_rebar_get_possible_sizes(pdev, LMEM_BAR_NUM);
> +		msb = __fls(rebar);
> +
> +		for (k = msb; k >= 0; k--) {
> +			set_bit = (1 << k);
> +
> +			if (set_bit & rebar)
> +				if (set_bit == lmem_bar_size) {
> +					rebar_size = 1ULL << (__fls(lmem_bar_size) + BAR_SIZE_SHIFT);
> +
> +					if (rebar_size == pci_resource_len(pdev, LMEM_BAR_NUM))
> +						return;
> +					break;
> +				}
> +		}
> +	} else if (!rebar_size)
>   		return;
>   
>   	/* Find out if root bus contains 64bit memory addressing */
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index 701fbc98afa0..6fc475a5db61 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -204,6 +204,8 @@ i915_param_named_unsafe(request_timeout_ms, uint, 0600,
>   
>   i915_param_named_unsafe(lmem_size, uint, 0400,
>   			"Set the lmem size(in MiB) for each region. (default: 0, all memory)");
> +i915_param_named_unsafe(lmem_bar_size, uint, 0400,
> +			"Set the lmem bar size(in MiB).");
>   
>   static __always_inline void _print_param(struct drm_printer *p,
>   					 const char *name,
> diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> index b5e7ea45d191..2733cb6cfe09 100644
> --- a/drivers/gpu/drm/i915/i915_params.h
> +++ b/drivers/gpu/drm/i915/i915_params.h
> @@ -74,6 +74,7 @@ struct drm_printer;
>   	param(char *, force_probe, CONFIG_DRM_I915_FORCE_PROBE, 0400) \
>   	param(unsigned int, request_timeout_ms, CONFIG_DRM_I915_REQUEST_TIMEOUT, CONFIG_DRM_I915_REQUEST_TIMEOUT ? 0600 : 0) \
>   	param(unsigned int, lmem_size, 0, 0400) \
> +	param(unsigned int, lmem_bar_size, 0, 0400) \
>   	/* leave bools at the end to not create holes */ \
>   	param(bool, enable_hangcheck, true, 0600) \
>   	param(bool, load_detect_test, false, 0600) \