Re: [PATCH v4] drm/i915/bxt: Broxton decoupled MMIO

[Praveen Paneri <praveen.paneri@intel.com>]

Hi Chris,

On Tuesday 15 November 2016 03:37 PM, Chris Wilson wrote:
> On Tue, Nov 15, 2016 at 09:36:34AM +0000, Tvrtko Ursulin wrote:
>>
>> On 15/11/2016 06:40, Praveen Paneri wrote:
>>> Decoupled MMIO is an alternative way to access forcewake domain
>>> registers, which requires less cycles for a single read/write and
>>> avoids frequent software forcewake.
>>> This certainly gives advantage over the forcewake as this new
>>> mechanism “decouples” CPU cycles and allow them to complete even
>>> when GT is in a CPD (frequency change) or C6 state.
>>>
>>> This can co-exist with forcewake and we will continue to use forcewake
>>> as appropriate. E.g. 64-bit register writes to avoid writing 2 dwords
>>> separately and land into funny situations.
>>>
>>> v2:
>>> - Moved platform check out of the function and got rid of duplicate
>>> functions to find out decoupled power domain (Chris)
>>> - Added a check for forcewake already held and skipped decoupled
>>> access (Chris)
>>> - Skipped writing 64 bit registers through decoupled MMIO (Chris)
>>>
>>> v3:
>>> - Improved commit message with more info on decoupled mmio (Tvrtko)
>>> - Changed decoupled operation to enum and used u32 instead of
>>> uint_32 data type for register offset (Tvrtko)
>>> - Moved HAS_DECOUPLED_MMIO to device info (Tvrtko)
>>> - Added lookup table for converting fw_engine to pd_engine (Tvrtko)
>>> - Improved __gen9_decoupled_read and __gen9_decoupled_write
>>> routines (Tvrtko)
>>>
>>> v4:
>>> - Fixed alignment and variable names (Chris)
>>> - Write GEN9_DECOUPLED_REG0_DW1 register in just one go (Zhe Wang)
>>>
>>> Signed-off-by: Zhe Wang <zhe1.wang@intel.com>
>>> Signed-off-by: Praveen Paneri <praveen.paneri@intel.com>
>>> ---
>>> drivers/gpu/drm/i915/i915_drv.h     |  18 +++++-
>>> drivers/gpu/drm/i915/i915_pci.c     |   1 +
>>> drivers/gpu/drm/i915/i915_reg.h     |   7 +++
>>> drivers/gpu/drm/i915/intel_uncore.c | 109 ++++++++++++++++++++++++++++++++++++
>>> 4 files changed, 134 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>>> index 4e7148a..158f05c 100644
>>> --- a/drivers/gpu/drm/i915/i915_drv.h
>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>>> @@ -549,6 +549,18 @@ enum forcewake_domains {
>>> #define FW_REG_READ  (1)
>>> #define FW_REG_WRITE (2)
>>>
>>> +enum decoupled_power_domain {
>>> +	GEN9_DECOUPLED_PD_BLITTER = 0,
>>> +	GEN9_DECOUPLED_PD_RENDER,
>>> +	GEN9_DECOUPLED_PD_MEDIA,
>>> +	GEN9_DECOUPLED_PD_ALL
>>> +};
>>> +
>>> +enum decoupled_ops {
>>> +	GEN9_DECOUPLED_OP_WRITE = 0,
>>> +	GEN9_DECOUPLED_OP_READ
>>> +};
>>> +
>>> enum forcewake_domains
>>> intel_uncore_forcewake_for_reg(struct drm_i915_private *dev_priv,
>>> 			       i915_reg_t reg, unsigned int op);
>>> @@ -683,7 +695,8 @@ struct intel_csr {
>>> 	func(cursor_needs_physical); \
>>> 	func(hws_needs_physical); \
>>> 	func(overlay_needs_physical); \
>>> -	func(supports_tv)
>>> +	func(supports_tv); \
>>> +	func(has_decoupled_mmio)
>>>
>>> struct sseu_dev_info {
>>> 	u8 slice_mask;
>>> @@ -2652,6 +2665,9 @@ struct drm_i915_cmd_table {
>>> #define GT_FREQUENCY_MULTIPLIER 50
>>> #define GEN9_FREQ_SCALER 3
>>>
>>> +#define HAS_DECOUPLED_MMIO(dev) (INTEL_INFO(dev)->has_decoupled_mmio \
>>> +		&& IS_BXT_REVID(dev, BXT_REVID_C0, REVID_FOREVER))
>>> +
>>
>> Looks like I've missed this before, but Would you mind renaming the
>> dev argument to dev_priv?
>
> And whilst you are there, fix up the code to set
> info->has_decoupled_mmio = false when santizing.
> -Chris
but dev_priv->info is declared as const.

Praveen
>
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