linux-kernel - Re: [PATCH 07/11] bus: mhi: host: core: Add overflow disable flag

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Message-ID: <vzmacvzafgrtxupg6cmm2bi5kxuzyeoeod56qzp5ftlnh4txlj@xni5cok2lj3j>
Date: Tue, 13 Jan 2026 13:44:00 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Sivareddy Surasani <sivareddy.surasani@....qualcomm.com>
Cc: Jonathan Corbet <corbet@....net>, Arnd Bergmann <arnd@...db.de>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, 
	Upal Kumar Saha <upal.saha@....qualcomm.com>, Himanshu Shukla <quic_himashuk@...cinc.com>, 
	Vivek Pernamitta <vivek.pernamitta@....qualcomm.com>
Subject: Re: [PATCH 07/11] bus: mhi: host: core: Add overflow disable flag

On Thu, Dec 11, 2025 at 01:37:39PM +0530, Sivareddy Surasani wrote:
> From: Vivek Pernamitta <vivek.pernamitta@....qualcomm.com>
> 
> When the client transfers a large packet, the host may set
> overflow events if the packet size exceeds the transfer ring
> element size. Add a flag to disable overflow events.
> 
> Scenario: A device sends a packet of 5000 bytes. The host has
> buffers of 2048 bytes, so the packet is split across three
> buffers. The host expects one event for the entire packet, but
> three events are generated: two marked as overflow and the
> third as end of packet. The client driver wants only one
> callback for the EOT event, not for overflow events. This
> change prevents host channels from generating overflow events.
> 
> Signed-off-by: Vivek Pernamitta <vivek.pernamitta@....qualcomm.com>

Great, you just broke bisectability. This patch should come before 06/11 which
uses this flag.

- Mani

> Signed-off-by: Sivareddy Surasani <sivareddy.surasani@....qualcomm.com>
> ---
>  drivers/bus/mhi/common.h        | 3 ++-
>  drivers/bus/mhi/host/init.c     | 3 +++
>  drivers/bus/mhi/host/internal.h | 1 +
>  include/linux/mhi.h             | 2 ++
>  4 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
> index 58f27c6ba63e..31ff4d2e6eba 100644
> --- a/drivers/bus/mhi/common.h
> +++ b/drivers/bus/mhi/common.h
> @@ -282,7 +282,8 @@ struct mhi_event_ctxt {
>  #define CHAN_CTX_CHSTATE_MASK		GENMASK(7, 0)
>  #define CHAN_CTX_BRSTMODE_MASK		GENMASK(9, 8)
>  #define CHAN_CTX_POLLCFG_MASK		GENMASK(15, 10)
> -#define CHAN_CTX_RESERVED_MASK		GENMASK(31, 16)
> +#define CHAN_CTX_OVF_DISABLE_MASK	GENMASK(17, 16)
> +#define CHAN_CTX_RESERVED_MASK		GENMASK(31, 18)
>  struct mhi_chan_ctxt {
>  	__le32 chcfg;
>  	__le32 chtype;
> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
> index 4c092490c9fd..50f96f2c823f 100644
> --- a/drivers/bus/mhi/host/init.c
> +++ b/drivers/bus/mhi/host/init.c
> @@ -340,6 +340,8 @@ static int mhi_init_dev_ctxt(struct mhi_controller *mhi_cntrl)
>  		tmp |= FIELD_PREP(CHAN_CTX_BRSTMODE_MASK, mhi_chan->db_cfg.brstmode);
>  		tmp &= ~CHAN_CTX_POLLCFG_MASK;
>  		tmp |= FIELD_PREP(CHAN_CTX_POLLCFG_MASK, mhi_chan->db_cfg.pollcfg);
> +		tmp &= ~CHAN_CTX_OVF_DISABLE_MASK;
> +		tmp |= FIELD_PREP(CHAN_CTX_OVF_DISABLE_MASK, mhi_chan->db_cfg.ovf_dis);
>  		chan_ctxt->chcfg = cpu_to_le32(tmp);
>  
>  		chan_ctxt->chtype = cpu_to_le32(mhi_chan->type);
> @@ -870,6 +872,7 @@ static int parse_ch_cfg(struct mhi_controller *mhi_cntrl,
>  
>  		mhi_chan->ee_mask = ch_cfg->ee_mask;
>  		mhi_chan->db_cfg.pollcfg = ch_cfg->pollcfg;
> +		mhi_chan->db_cfg.ovf_dis = ch_cfg->ovf_disable;
>  		mhi_chan->lpm_notify = ch_cfg->lpm_notify;
>  		mhi_chan->offload_ch = ch_cfg->offload_channel;
>  		mhi_chan->db_cfg.reset_req = ch_cfg->doorbell_mode_switch;
> diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
> index 97bf6a70b9fa..db00ede0aa48 100644
> --- a/drivers/bus/mhi/host/internal.h
> +++ b/drivers/bus/mhi/host/internal.h
> @@ -189,6 +189,7 @@ struct db_cfg {
>  	bool reset_req;
>  	bool db_mode;
>  	u32 pollcfg;
> +	bool ovf_dis;
>  	enum mhi_db_brst_mode brstmode;
>  	dma_addr_t db_val;
>  	void (*process_db)(struct mhi_controller *mhi_cntrl,
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index 299216b5e4de..926a20835467 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -215,6 +215,7 @@ enum mhi_db_brst_mode {
>   * @ee_mask: Execution Environment mask for this channel
>   * @pollcfg: Polling configuration for burst mode.  0 is default.  milliseconds
>  	     for UL channels, multiple of 8 ring elements for DL channels
> + * @ovf_disbale: Overflow disable flag
>   * @doorbell: Doorbell mode
>   * @lpm_notify: The channel master requires low power mode notifications
>   * @offload_channel: The client manages the channel completely
> @@ -232,6 +233,7 @@ struct mhi_channel_config {
>  	enum mhi_ch_type type;
>  	u32 ee_mask;
>  	u32 pollcfg;
> +	bool ovf_disable;
>  	enum mhi_db_brst_mode doorbell;
>  	bool lpm_notify;
>  	bool offload_channel;
> 
> -- 
> 2.34.1
> 

-- 
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