Re: [PATCH v3 04/13] drm/i915/gen9: Remove csr.state, csr_lock and related code.

[Animesh Manna <animesh.manna@xxxxxxxxx>]

On 10/29/2015 3:28 AM, Imre Deak wrote:
> From: Daniel Vetter <daniel.vetter@xxxxxxxxx>
>
> This removes two anti-patterns:
> - Locking shouldn't be used to synchronize with async work (of any
>    form, whether callbacks, workers or other threads). This is what the
>    mutex_lock/unlock seems to have been for in intel_csr_load_program.
>    Instead ordering should be ensured with the generic
>    wait_for_completion()/complete(). Or more specific functions
>    provided by the core kernel like e.g.
>    flush_work()/cancel_work_sync() in the case of synchronizing with a
>    work item.
>
> - Don't invent own completion like the following code did with the
>    (already removed) wait_for(csr_load_status_get()) pattern - it's
>    really hard to get these right when you want them to be _really_
>    correct (and be fast) in all cases. Furthermore it's easier to read
>    code using the well-known primitives than new ones using
>    non-standard names.
>
> Before enabling/disabling DC6 check if the firmware is loaded
> successfully. This is guaranteed during runtime s/r, since otherwise we
> don't enable RPM, but not during system s/r.
Yes as DC5 and DC6 display low power state is coupled with dmc firmware 
so it is a safe
to have a check before enable/disable dc5/dc6.
> Note that it's still unclear whether we need to enable/disable DC6
> during system s/r, until that's clarified, keep the current behavior and
> enable/disable DC6.
>
> Also after this patch there is a race during system s/r where the
> firmware may not be loaded yet, that's addressed in an upcoming patch.
>
> Cc: Damien Lespiau <damien.lespiau@xxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxx>
> Cc: Sunil Kamath <sunil.kamath@xxxxxxxxx>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> Signed-off-by: Animesh Manna <animesh.manna@xxxxxxxxx>
> [imre: added code and note about checking if the firmware loaded ok,
>   before enabling/disabling it]
Reviewed-by: Animesh Manna <animesh.manna@xxxxxxxxx>
> ---
>   drivers/gpu/drm/i915/i915_dma.c         |  1 -
>   drivers/gpu/drm/i915/i915_drv.c         | 11 ++------
>   drivers/gpu/drm/i915/i915_drv.h         | 10 -------
>   drivers/gpu/drm/i915/i915_gpu_error.c   |  2 +-
>   drivers/gpu/drm/i915/intel_csr.c        | 46 +--------------------------------
>   drivers/gpu/drm/i915/intel_drv.h        |  3 ---
>   drivers/gpu/drm/i915/intel_runtime_pm.c | 17 ++----------
>   7 files changed, 6 insertions(+), 84 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 5d68942..621914c 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -897,7 +897,6 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
>   	spin_lock_init(&dev_priv->mmio_flip_lock);
>   	mutex_init(&dev_priv->sb_lock);
>   	mutex_init(&dev_priv->modeset_restore_lock);
> -	mutex_init(&dev_priv->csr_lock);
>   	mutex_init(&dev_priv->av_mutex);
>   
>   	intel_pm_setup(dev);
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 121c539..7efc798 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1050,18 +1050,11 @@ static int i915_pm_resume(struct device *dev)
>   
>   static int skl_suspend_complete(struct drm_i915_private *dev_priv)
>   {
> -	enum csr_state state;
>   	/* Enabling DC6 is not a hard requirement to enter runtime D3 */
>   
>   	skl_uninit_cdclk(dev_priv);
>   
> -	/* TODO: wait for a completion event or
> -	 * similar here instead of busy
> -	 * waiting using wait_for function.
> -	 */
> -	wait_for((state = intel_csr_load_status_get(dev_priv)) !=
> -			FW_UNINITIALIZED, 1000);
> -	if (state == FW_LOADED)
> +	if (dev_priv->csr.dmc_payload)
>   		skl_enable_dc6(dev_priv);
>   
>   	return 0;
> @@ -1110,7 +1103,7 @@ static int skl_resume_prepare(struct drm_i915_private *dev_priv)
>   {
>   	struct drm_device *dev = dev_priv->dev;
>   
> -	if (intel_csr_load_status_get(dev_priv) == FW_LOADED)
> +	if (dev_priv->csr.dmc_payload)
>   		skl_disable_dc6(dev_priv);
>   
>   	skl_init_cdclk(dev_priv);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 0bee438..0aeac06 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -738,12 +738,6 @@ struct intel_uncore {
>   #define CSR_VERSION_MAJOR(version)	((version) >> 16)
>   #define CSR_VERSION_MINOR(version)	((version) & 0xffff)
>   
> -enum csr_state {
> -	FW_UNINITIALIZED = 0,
> -	FW_LOADED,
> -	FW_FAILED
> -};
> -
>   struct intel_csr {
>   	const char *fw_path;
>   	uint32_t *dmc_payload;
> @@ -752,7 +746,6 @@ struct intel_csr {
>   	uint32_t mmio_count;
>   	uint32_t mmioaddr[8];
>   	uint32_t mmiodata[8];
> -	enum csr_state state;
>   };
>   
>   #define DEV_INFO_FOR_EACH_FLAG(func, sep) \
> @@ -1724,9 +1717,6 @@ struct drm_i915_private {
>   
>   	struct intel_csr csr;
>   
> -	/* Display CSR-related protection */
> -	struct mutex csr_lock;
> -
>   	struct intel_gmbus gmbus[GMBUS_NUM_PINS];
>   
>   	/** gmbus_mutex protects against concurrent usage of the single hw gmbus
> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> index aaf4a1f..25dc4f1 100644
> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> @@ -370,7 +370,7 @@ int i915_error_state_to_str(struct drm_i915_error_state_buf *m,
>   	if (HAS_CSR(dev)) {
>   		struct intel_csr *csr = &dev_priv->csr;
>   
> -		err_printf(m, "DMC load state: %d\n", csr->state);
> +		err_printf(m, "DMC loaded: %s\n", yesno(csr->dmc_payload));
>   		err_printf(m, "DMC fw version: %d.%d\n",
>   			   CSR_VERSION_MAJOR(csr->version),
>   			   CSR_VERSION_MINOR(csr->version));
> diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
> index cd6fb58d..eddad62 100644
> --- a/drivers/gpu/drm/i915/intel_csr.c
> +++ b/drivers/gpu/drm/i915/intel_csr.c
> @@ -203,40 +203,6 @@ static char intel_get_substepping(struct drm_device *dev)
>   }
>   
>   /**
> - * intel_csr_load_status_get() - to get firmware loading status.
> - * @dev_priv: i915 device.
> - *
> - * This function helps to get the firmware loading status.
> - *
> - * Return: Firmware loading status.
> - */
> -enum csr_state intel_csr_load_status_get(struct drm_i915_private *dev_priv)
> -{
> -	enum csr_state state;
> -
> -	mutex_lock(&dev_priv->csr_lock);
> -	state = dev_priv->csr.state;
> -	mutex_unlock(&dev_priv->csr_lock);
> -
> -	return state;
> -}
> -
> -/**
> - * intel_csr_load_status_set() - help to set firmware loading status.
> - * @dev_priv: i915 device.
> - * @state: enumeration of firmware loading status.
> - *
> - * Set the firmware loading status.
> - */
> -void intel_csr_load_status_set(struct drm_i915_private *dev_priv,
> -			enum csr_state state)
> -{
> -	mutex_lock(&dev_priv->csr_lock);
> -	dev_priv->csr.state = state;
> -	mutex_unlock(&dev_priv->csr_lock);
> -}
> -
> -/**
>    * intel_csr_load_program() - write the firmware from memory to register.
>    * @dev: drm device.
>    *
> @@ -264,7 +230,6 @@ void intel_csr_load_program(struct drm_device *dev)
>   	if (I915_READ(CSR_PROGRAM(0)))
>   		return;
>   
> -	mutex_lock(&dev_priv->csr_lock);
>   	fw_size = dev_priv->csr.dmc_fw_size;
>   	for (i = 0; i < fw_size; i++)
>   		I915_WRITE(CSR_PROGRAM(i), payload[i]);
> @@ -273,9 +238,6 @@ void intel_csr_load_program(struct drm_device *dev)
>   		I915_WRITE(dev_priv->csr.mmioaddr[i],
>   			dev_priv->csr.mmiodata[i]);
>   	}
> -
> -	dev_priv->csr.state = FW_LOADED;
> -	mutex_unlock(&dev_priv->csr_lock);
>   }
>   
>   static void finish_csr_load(const struct firmware *fw, void *context)
> @@ -415,8 +377,6 @@ out:
>   			 CSR_VERSION_MAJOR(csr->version),
>   			 CSR_VERSION_MINOR(csr->version));
>   	} else {
> -		intel_csr_load_status_set(dev_priv, FW_FAILED);
> -
>   		i915_firmware_load_error_print(csr->fw_path, 0);
>   	}
>   
> @@ -445,7 +405,6 @@ void intel_csr_ucode_init(struct drm_device *dev)
>   		csr->fw_path = I915_CSR_BXT;
>   	else {
>   		DRM_ERROR("Unexpected: no known CSR firmware for platform\n");
> -		intel_csr_load_status_set(dev_priv, FW_FAILED);
>   		return;
>   	}
>   
> @@ -462,10 +421,8 @@ void intel_csr_ucode_init(struct drm_device *dev)
>   				&dev_priv->dev->pdev->dev,
>   				GFP_KERNEL, dev_priv,
>   				finish_csr_load);
> -	if (ret) {
> +	if (ret)
>   		i915_firmware_load_error_print(csr->fw_path, ret);
> -		intel_csr_load_status_set(dev_priv, FW_FAILED);
> -	}
>   }
>   
>   /**
> @@ -482,6 +439,5 @@ void intel_csr_ucode_fini(struct drm_device *dev)
>   	if (!HAS_CSR(dev))
>   		return;
>   
> -	intel_csr_load_status_set(dev_priv, FW_FAILED);
>   	kfree(dev_priv->csr.dmc_payload);
>   }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 3d1c744..2e48b3f 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1206,9 +1206,6 @@ u32 skl_plane_ctl_rotation(unsigned int rotation);
>   
>   /* intel_csr.c */
>   void intel_csr_ucode_init(struct drm_device *dev);
> -enum csr_state intel_csr_load_status_get(struct drm_i915_private *dev_priv);
> -void intel_csr_load_status_set(struct drm_i915_private *dev_priv,
> -					enum csr_state state);
>   void intel_csr_load_program(struct drm_device *dev);
>   void intel_csr_ucode_fini(struct drm_device *dev);
>   
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index 92746e1..30b5801 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -664,8 +664,7 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
>   	} else {
>   		if (enable_requested) {
>   			if (IS_SKYLAKE(dev) &&
> -				(power_well->data == SKL_DISP_PW_1) &&
> -				(intel_csr_load_status_get(dev_priv) == FW_LOADED))
> +				(power_well->data == SKL_DISP_PW_1))
>   				DRM_DEBUG_KMS("Not Disabling PW1, dmc will handle\n");
>   			else {
>   				I915_WRITE(HSW_PWR_WELL_DRIVER,	tmp & ~req_mask);
> @@ -674,20 +673,8 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
>   			}
>   
>   			if (GEN9_ENABLE_DC5(dev) &&
> -				power_well->data == SKL_DISP_PW_2) {
> -				enum csr_state state;
> -				/* TODO: wait for a completion event or
> -				 * similar here instead of busy
> -				 * waiting using wait_for function.
> -				 */
> -				wait_for((state = intel_csr_load_status_get(dev_priv)) !=
> -						FW_UNINITIALIZED, 1000);
> -				if (state != FW_LOADED)
> -					DRM_DEBUG("CSR firmware not ready (%d)\n",
> -							state);
> -				else
> +				power_well->data == SKL_DISP_PW_2)
>   					gen9_enable_dc5(dev_priv);
> -			}
>   		}
>   	}
>   

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