linux-kernel - Re: [PATCH v2] mailbox: qcom-ipcc: Reset CLEAR_ON_RECV

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Message-ID: <20250124075646.oc6ni5gp6c23ozp7@thinkpad>
Date: Fri, 24 Jan 2025 13:26:46 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
Cc: manivannan.sadhasivam@...aro.org, jassisinghbrar@...il.com,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mailbox: qcom-ipcc: Reset CLEAR_ON_RECV_RD if set
 from boot firmware

On Mon, Dec 30, 2024 at 01:24:25PM +0530, Mukesh Ojha wrote:
> For some SoCs, boot firmware is using the same IPCC instance used
> by Linux and it has kept CLEAR_ON_RECV_RD set which basically means
> interrupt pending registers are cleared when RECV_ID is read and the
> register automatically updates to the next pending interrupt/client
> status based on priority.
> 
> Clear the CLEAR_ON_RECV_RD if it is set from the boot firmware.
> 

Any user visible implications due to this?

> Signed-off-by: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
> ---
> Change in v2:
>  - Corrected email id in the Sob.
> 
>  drivers/mailbox/qcom-ipcc.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/mailbox/qcom-ipcc.c b/drivers/mailbox/qcom-ipcc.c
> index 14c7907c6632..0b17a38ea6bf 100644
> --- a/drivers/mailbox/qcom-ipcc.c
> +++ b/drivers/mailbox/qcom-ipcc.c
> @@ -14,6 +14,7 @@
>  #include <dt-bindings/mailbox/qcom-ipcc.h>
>  
>  /* IPCC Register offsets */
> +#define IPCC_REG_CONFIG			0x08
>  #define IPCC_REG_SEND_ID		0x0c
>  #define IPCC_REG_RECV_ID		0x10
>  #define IPCC_REG_RECV_SIGNAL_ENABLE	0x14
> @@ -21,6 +22,7 @@
>  #define IPCC_REG_RECV_SIGNAL_CLEAR	0x1c
>  #define IPCC_REG_CLIENT_CLEAR		0x38
>  
> +#define IPCC_CLEAR_ON_RECV_RD		BIT(0)
>  #define IPCC_SIGNAL_ID_MASK		GENMASK(15, 0)
>  #define IPCC_CLIENT_ID_MASK		GENMASK(31, 16)
>  
> @@ -274,6 +276,7 @@ static int qcom_ipcc_pm_resume(struct device *dev)
>  static int qcom_ipcc_probe(struct platform_device *pdev)
>  {
>  	struct qcom_ipcc *ipcc;
> +	u32 config_value;
>  	static int id;
>  	char *name;
>  	int ret;
> @@ -288,6 +291,19 @@ static int qcom_ipcc_probe(struct platform_device *pdev)
>  	if (IS_ERR(ipcc->base))
>  		return PTR_ERR(ipcc->base);
>  
> +	/*
> +	 * It is possible that boot firmware is using the same IPCC instance
> +	 * as of the HLOS and it has kept CLEAR_ON_RECV_RD set which basically
> +	 * means Interrupt pending registers are cleared when RECV_ID is read.
> +	 * The register automatically updates to the next pending interrupt/client
> +	 * status based on priority.
> +	 */
> +	config_value = readl(ipcc->base + IPCC_REG_CONFIG);
> +	if (config_value & IPCC_CLEAR_ON_RECV_RD) {

Can't you just clear this bit always?

- Mani

-- 
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