[PATCH v2] mhi: pci_generic: No-Op for device_wake operations

[PATCH v2] mhi: pci_generic: No-Op for device_wake operations

[Loic Poulain]

The wake_db register presence is highly speculative and can fuze MHI
devices. Indeed, currently the wake_db register address is defined at
entry 127 of the 'Channel doorbell array', thus writing to this address
is equivalent to ringing the doorbell for channel 127, causing trouble
with some device that get an unexpected channel 127 doorbell interrupt.

This change fixes that issue by setting wake get/put as no-op for
pci_generic devices. The wake device sideband mechanism seems really
specific to each device, and is AFAIK no defined by the MHI spec.

It also removes zeroing initialization of wake_db register during MMIO
initialization, the register being set via wake_get/put accessors few
cycles later during M0 transition.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
---
 v2: add missing mhi core change

 drivers/bus/mhi/core/init.c   |  2 --
 drivers/bus/mhi/pci_generic.c | 18 ++++++++++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index 2159dbc..32eb90f 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -510,8 +510,6 @@ int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
 
 	/* Setup wake db */
 	mhi_cntrl->wake_db = base + val + (8 * MHI_DEV_WAKE_DB);
-	mhi_write_reg(mhi_cntrl, mhi_cntrl->wake_db, 4, 0);
-	mhi_write_reg(mhi_cntrl, mhi_cntrl->wake_db, 0, 0);
 	mhi_cntrl->wake_set = false;
 
 	/* Setup channel db address for each channel in tre_ring */
diff --git a/drivers/bus/mhi/pci_generic.c b/drivers/bus/mhi/pci_generic.c
index 4fc543c..d4e8c9c 100644
--- a/drivers/bus/mhi/pci_generic.c
+++ b/drivers/bus/mhi/pci_generic.c
@@ -347,6 +347,21 @@ static void mhi_pci_status_cb(struct mhi_controller *mhi_cntrl,
 	}
 }
 
+static void mhi_pci_wake_get_nop(struct mhi_controller *mhi_cntrl, bool force)
+{
+	/* no-op */
+}
+
+static void mhi_pci_wake_put_nop(struct mhi_controller *mhi_cntrl, bool override)
+{
+	/* no-op */
+}
+
+static void mhi_pci_wake_toggle_nop(struct mhi_controller *mhi_cntrl)
+{
+	/* no-op */
+}
+
 static bool mhi_pci_is_alive(struct mhi_controller *mhi_cntrl)
 {
 	struct pci_dev *pdev = to_pci_dev(mhi_cntrl->cntrl_dev);
@@ -550,6 +565,9 @@ static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	mhi_cntrl->status_cb = mhi_pci_status_cb;
 	mhi_cntrl->runtime_get = mhi_pci_runtime_get;
 	mhi_cntrl->runtime_put = mhi_pci_runtime_put;
+	mhi_cntrl->wake_get = mhi_pci_wake_get_nop;
+	mhi_cntrl->wake_put = mhi_pci_wake_put_nop;
+	mhi_cntrl->wake_toggle = mhi_pci_wake_toggle_nop;
 
 	err = mhi_pci_claim(mhi_cntrl, info->bar_num, DMA_BIT_MASK(info->dma_data_width));
 	if (err)
-- 
2.7.4

Re: [PATCH v2] mhi: pci_generic: No-Op for device_wake operations

[patchwork-bot+linux-arm-msm]

Hello:

This patch was applied to qcom/linux.git (refs/heads/for-next):

On Tue, 23 Feb 2021 17:13:01 +0100 you wrote:
> The wake_db register presence is highly speculative and can fuze MHI
> devices. Indeed, currently the wake_db register address is defined at
> entry 127 of the 'Channel doorbell array', thus writing to this address
> is equivalent to ringing the doorbell for channel 127, causing trouble
> with some device that get an unexpected channel 127 doorbell interrupt.
> 
> This change fixes that issue by setting wake get/put as no-op for
> pci_generic devices. The wake device sideband mechanism seems really
> specific to each device, and is AFAIK no defined by the MHI spec.
> 
> [...]

Here is the summary with links:
  - [v2] mhi: pci_generic: No-Op for device_wake operations
    https://git.kernel.org/qcom/c/e3e5e6508fc1

You are awesome, thank you!
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