Re: [PATCH v7 01/10] bus: mhi: core: Add device hardware reset support

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

On Mon, Jan 04, 2021 at 02:49:30PM +0100, Loic Poulain wrote:
> The MHI specification allows to perform a hard reset of the device
> when writing to the SOC_RESET register. It can be used to completely
> restart the device (e.g. in case of unrecoverable MHI error).
> 
> This is up to the MHI controller driver to determine when this hard
> reset should be used, and in case of MHI errors, should be used as
> a reset of last resort (after standard MHI stack reset).
> 
> This function is a stateless function, the MHI layer do nothing except
> triggering the reset by writing into the right register(s), this is up
> to the caller to ensure right mhi_controller state (e.g. unregister the
> controller if necessary).
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>

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

Thanks,
Mani

> ---
>  drivers/bus/mhi/core/main.c | 13 +++++++++++++
>  include/linux/mhi.h         |  9 +++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index a353d1e..c181a85 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -142,6 +142,19 @@ enum mhi_state mhi_get_mhi_state(struct mhi_controller *mhi_cntrl)
>  }
>  EXPORT_SYMBOL_GPL(mhi_get_mhi_state);
>  
> +void mhi_soc_reset(struct mhi_controller *mhi_cntrl)
> +{
> +	if (mhi_cntrl->reset) {
> +		mhi_cntrl->reset(mhi_cntrl);
> +		return;
> +	}
> +
> +	/* Generic MHI SoC reset */
> +	mhi_write_reg(mhi_cntrl, mhi_cntrl->regs, MHI_SOC_RESET_REQ_OFFSET,
> +		      MHI_SOC_RESET_REQ);
> +}
> +EXPORT_SYMBOL_GPL(mhi_soc_reset);
> +
>  int mhi_map_single_no_bb(struct mhi_controller *mhi_cntrl,
>  			 struct mhi_buf_info *buf_info)
>  {
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index 04cf7f3..7ddbcd7 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -355,6 +355,7 @@ struct mhi_controller_config {
>   * @unmap_single: CB function to destroy TRE buffer
>   * @read_reg: Read a MHI register via the physical link (required)
>   * @write_reg: Write a MHI register via the physical link (required)
> + * @reset: Controller specific reset function (optional)
>   * @buffer_len: Bounce buffer length
>   * @index: Index of the MHI controller instance
>   * @bounce_buf: Use of bounce buffer
> @@ -445,6 +446,7 @@ struct mhi_controller {
>  			u32 *out);
>  	void (*write_reg)(struct mhi_controller *mhi_cntrl, void __iomem *addr,
>  			  u32 val);
> +	void (*reset)(struct mhi_controller *mhi_cntrl);
>  
>  	size_t buffer_len;
>  	int index;
> @@ -681,6 +683,13 @@ enum mhi_ee_type mhi_get_exec_env(struct mhi_controller *mhi_cntrl);
>  enum mhi_state mhi_get_mhi_state(struct mhi_controller *mhi_cntrl);
>  
>  /**
> + * mhi_soc_reset - Trigger a device reset. This can be used as a last resort
> + *		   to reset and recover a device.
> + * @mhi_cntrl: MHI controller
> + */
> +void mhi_soc_reset(struct mhi_controller *mhi_cntrl);
> +
> +/**
>   * mhi_device_get - Disable device low power mode
>   * @mhi_dev: Device associated with the channel
>   */
> -- 
> 2.7.4
>