Re: [PATCH v7 04/10] mhi: pci_generic: Add support for reset

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Mon, Jan 04, 2021 at 02:49:33PM +0100, Loic Poulain wrote:
> Add support for resetting the device, reset can be triggered in case
> of error or manually via sysfs (/sys/bus/pci/devices/*/reset).
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> ---
>  drivers/bus/mhi/pci_generic.c | 121 +++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 108 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/bus/mhi/pci_generic.c b/drivers/bus/mhi/pci_generic.c
> index 077595c..b2307e7 100644
> --- a/drivers/bus/mhi/pci_generic.c
> +++ b/drivers/bus/mhi/pci_generic.c
> @@ -8,6 +8,7 @@
>   * Copyright (C) 2020 Linaro Ltd <loic.poulain@linaro.org>
>   */
>  
> +#include <linux/delay.h>
>  #include <linux/device.h>
>  #include <linux/mhi.h>
>  #include <linux/module.h>
> @@ -15,6 +16,7 @@
>  
>  #define MHI_PCI_DEFAULT_BAR_NUM 0
>  
> +#define MHI_POST_RESET_DELAY_MS 500
>  /**
>   * struct mhi_pci_dev_info - MHI PCI device specific information
>   * @config: MHI controller configuration
> @@ -177,6 +179,16 @@ static const struct pci_device_id mhi_pci_id_table[] = {
>  };
>  MODULE_DEVICE_TABLE(pci, mhi_pci_id_table);
>  
> +enum mhi_pci_device_status {
> +	MHI_PCI_DEV_STARTED,
> +};
> +
> +struct mhi_pci_device {
> +	struct mhi_controller mhi_cntrl;
> +	struct pci_saved_state *pci_state;
> +	unsigned long status;
> +};
> +
>  static int mhi_pci_read_reg(struct mhi_controller *mhi_cntrl,
>  			    void __iomem *addr, u32 *out)
>  {
> @@ -196,6 +208,20 @@ static void mhi_pci_status_cb(struct mhi_controller *mhi_cntrl,
>  	/* Nothing to do for now */
>  }
>  
> +static bool mhi_pci_is_alive(struct mhi_controller *mhi_cntrl)
> +{
> +	struct pci_dev *pdev = to_pci_dev(mhi_cntrl->cntrl_dev);
> +	u16 vendor = 0;
> +
> +	if (pci_read_config_word(pdev, PCI_VENDOR_ID, &vendor))
> +		return false;
> +
> +	if (vendor == (u16) ~0 || vendor == 0)
> +		return false;
> +
> +	return true;
> +}
> +
>  static int mhi_pci_claim(struct mhi_controller *mhi_cntrl,
>  			 unsigned int bar_num, u64 dma_mask)
>  {
> @@ -291,16 +317,20 @@ static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  {
>  	const struct mhi_pci_dev_info *info = (struct mhi_pci_dev_info *) id->driver_data;
>  	const struct mhi_controller_config *mhi_cntrl_config;
> +	struct mhi_pci_device *mhi_pdev;
>  	struct mhi_controller *mhi_cntrl;
>  	int err;
>  
>  	dev_dbg(&pdev->dev, "MHI PCI device found: %s\n", info->name);
>  
> -	mhi_cntrl = mhi_alloc_controller();
> -	if (!mhi_cntrl)
> +	/* mhi_pdev.mhi_cntrl must be zero-initialized */
> +	mhi_pdev = devm_kzalloc(&pdev->dev, sizeof(*mhi_pdev), GFP_KERNEL);
> +	if (!mhi_pdev)
>  		return -ENOMEM;
>  
>  	mhi_cntrl_config = info->config;
> +	mhi_cntrl = &mhi_pdev->mhi_cntrl;
> +
>  	mhi_cntrl->cntrl_dev = &pdev->dev;
>  	mhi_cntrl->iova_start = 0;
>  	mhi_cntrl->iova_stop = DMA_BIT_MASK(info->dma_data_width);
> @@ -315,17 +345,21 @@ static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  
>  	err = mhi_pci_claim(mhi_cntrl, info->bar_num, DMA_BIT_MASK(info->dma_data_width));
>  	if (err)
> -		goto err_release;
> +		return err;
>  
>  	err = mhi_pci_get_irqs(mhi_cntrl, mhi_cntrl_config);
>  	if (err)
> -		goto err_release;
> +		return err;
> +
> +	pci_set_drvdata(pdev, mhi_pdev);
>  
> -	pci_set_drvdata(pdev, mhi_cntrl);
> +	/* Have stored pci confspace at hand for restore in sudden PCI error */
> +	pci_save_state(pdev);
> +	mhi_pdev->pci_state = pci_store_saved_state(pdev);
>  
>  	err = mhi_register_controller(mhi_cntrl, mhi_cntrl_config);
>  	if (err)
> -		goto err_release;
> +		return err;
>  
>  	/* MHI bus does not power up the controller by default */
>  	err = mhi_prepare_for_power_up(mhi_cntrl);
> @@ -340,33 +374,94 @@ static int mhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  		goto err_unprepare;
>  	}
>  
> +	set_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status);
> +
>  	return 0;
>  
>  err_unprepare:
>  	mhi_unprepare_after_power_down(mhi_cntrl);
>  err_unregister:
>  	mhi_unregister_controller(mhi_cntrl);
> -err_release:
> -	mhi_free_controller(mhi_cntrl);
>  
>  	return err;
>  }
>  
>  static void mhi_pci_remove(struct pci_dev *pdev)
>  {
> -	struct mhi_controller *mhi_cntrl = pci_get_drvdata(pdev);
> +	struct mhi_pci_device *mhi_pdev = pci_get_drvdata(pdev);
> +	struct mhi_controller *mhi_cntrl = &mhi_pdev->mhi_cntrl;
> +
> +	if (test_and_clear_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status)) {
> +		mhi_power_down(mhi_cntrl, true);
> +		mhi_unprepare_after_power_down(mhi_cntrl);
> +	}
>  
> -	mhi_power_down(mhi_cntrl, true);
> -	mhi_unprepare_after_power_down(mhi_cntrl);
>  	mhi_unregister_controller(mhi_cntrl);
> -	mhi_free_controller(mhi_cntrl);
>  }
>  
> +static void mhi_pci_reset_prepare(struct pci_dev *pdev)
> +{
> +	struct mhi_pci_device *mhi_pdev = pci_get_drvdata(pdev);
> +	struct mhi_controller *mhi_cntrl = &mhi_pdev->mhi_cntrl;
> +
> +	dev_info(&pdev->dev, "reset\n");
> +
> +	/* Clean up MHI state */
> +	if (test_and_clear_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status)) {
> +		mhi_power_down(mhi_cntrl, false);
> +		mhi_unprepare_after_power_down(mhi_cntrl);
> +	}
> +
> +	/* cause internal device reset */
> +	mhi_soc_reset(mhi_cntrl);
> +
> +	/* Be sure device reset has been executed */
> +	msleep(MHI_POST_RESET_DELAY_MS);
> +}
> +
> +static void mhi_pci_reset_done(struct pci_dev *pdev)
> +{
> +	struct mhi_pci_device *mhi_pdev = pci_get_drvdata(pdev);
> +	struct mhi_controller *mhi_cntrl = &mhi_pdev->mhi_cntrl;
> +	int err;
> +
> +	/* Restore initial known working PCI state */
> +	pci_load_saved_state(pdev, mhi_pdev->pci_state);
> +	pci_restore_state(pdev);
> +
> +	/* Is device status available ? */
> +	if (!mhi_pci_is_alive(mhi_cntrl)) {
> +		dev_err(&pdev->dev, "reset failed\n");
> +		return;
> +	}
> +
> +	err = mhi_prepare_for_power_up(mhi_cntrl);
> +	if (err) {
> +		dev_err(&pdev->dev, "failed to prepare MHI controller\n");
> +		return;
> +	}
> +
> +	err = mhi_sync_power_up(mhi_cntrl);
> +	if (err) {
> +		dev_err(&pdev->dev, "failed to power up MHI controller\n");
> +		mhi_unprepare_after_power_down(mhi_cntrl);
> +		return;
> +	}
> +
> +	set_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status);
> +}
> +
> +static const struct pci_error_handlers mhi_pci_err_handler = {
> +	.reset_prepare = mhi_pci_reset_prepare,
> +	.reset_done = mhi_pci_reset_done,
> +};
> +
>  static struct pci_driver mhi_pci_driver = {
>  	.name		= "mhi-pci-generic",
>  	.id_table	= mhi_pci_id_table,
>  	.probe		= mhi_pci_probe,
> -	.remove		= mhi_pci_remove
> +	.remove		= mhi_pci_remove,
> +	.err_handler	= &mhi_pci_err_handler,
>  };
>  module_pci_driver(mhi_pci_driver);
>  
> -- 
> 2.7.4
>