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

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 15/11/2016 13:17, Praveen Paneri wrote:
> 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.

Look in intel_device_info_runtime_init for how it is currently done 
(mkwrite_device_info).

Regards,

Tvrtko
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