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Date: Sat, 27 Jan 2024 21:43:45 -0600
From: Bjorn Andersson <andersson@kernel.org>
To: Maulik Shah <quic_mkshah@quicinc.com>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>, 
	linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, quic_eberman@quicinc.com, 
	quic_collinsd@quicinc.com, quic_lsrao@quicinc.com
Subject: Re: [PATCH v2] soc: qcom: rpmh-rsc: Enhance check for VREG in-flight
 request
Message-ID: <xjcefuurfbv7oquotsmm4iv4pnwzoone7jxrm42vjsnpfcgk4z@mnrsxec43bhp>
References: <20240119-rpmh-rsc-fixes-v2-1-e42c0a9e36f0@quicinc.com>
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In-Reply-To: <20240119-rpmh-rsc-fixes-v2-1-e42c0a9e36f0@quicinc.com>

On Fri, Jan 19, 2024 at 01:56:54PM +0530, Maulik Shah wrote:
> Each RPMh VREG accelerator resource has 3 or 4 contiguous 4-byte aligned
> addresses associated with it. These control voltage, enable state, mode,
> and in legacy targets, voltage headroom. The current in-flight request
> checking logic looks for exact address matches. Requests for different
> addresses of the same RPMh resource as thus not detected as in-flight.
> 
> Enhance the in-flight request check for VREG requests by ignoring the
> address offset. This ensures that only one request is allowed to be
> in-flight for a given VREG resource. This is needed to avoid scenarios
> where request commands are carried out by RPMh hardware out-of-order
> leading to LDO regulator over-current protection triggering.
> 
> Signed-off-by: Maulik Shah <quic_mkshah@quicinc.com>
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>

The s-o-b chain doesn't look right.

> ---
> Changes in v2:
> - Use GENMASK() and FIELD_GET()
> - Link to v1: https://lore.kernel.org/r/20240117-rpmh-rsc-fixes-v1-1-71ee4f8f72a4@quicinc.com
> ---
>  drivers/soc/qcom/rpmh-rsc.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> index a021dc71807b..e480cde783fe 100644
> --- a/drivers/soc/qcom/rpmh-rsc.c
> +++ b/drivers/soc/qcom/rpmh-rsc.c
> @@ -1,11 +1,13 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
>   * Copyright (c) 2016-2018, The Linux Foundation. All rights reserved.
> + * Copyright (c) 2023-2024, Qualcomm Innovation Center, Inc. All rights reserved.
>   */
>  
>  #define pr_fmt(fmt) "%s " fmt, KBUILD_MODNAME
>  
>  #include <linux/atomic.h>
> +#include <linux/bitfield.h>
>  #include <linux/cpu_pm.h>
>  #include <linux/delay.h>
>  #include <linux/interrupt.h>
> @@ -91,6 +93,15 @@ enum {
>  #define CMD_STATUS_ISSUED		BIT(8)
>  #define CMD_STATUS_COMPL		BIT(16)
>  
> +#define ACCL_TYPE(addr)			FIELD_GET(GENMASK(19, 16), addr)

Command DB is there so we don't have to make assumptions about the
addresses of resources. As such, I dislike this define.

> +#define VREG_ADDR(addr)			FIELD_GET(GENMASK(19, 4), addr)
> +
> +enum {
> +	HW_ACCL_CLK = 0x3,
> +	HW_ACCL_VREG,
> +	HW_ACCL_BUS,

We already define these in the kernel, but with different names:
CMD_DB_HW_ARC, CMD_DB_HW_VRM, CMD_DB_HW_BCM. I see no reason to use
different names for the same thing.

> +};
> +
>  /*
>   * Here's a high level overview of how all the registers in RPMH work
>   * together:
> @@ -557,7 +568,15 @@ static int check_for_req_inflight(struct rsc_drv *drv, struct tcs_group *tcs,
>  		for_each_set_bit(j, &curr_enabled, MAX_CMDS_PER_TCS) {
>  			addr = read_tcs_cmd(drv, drv->regs[RSC_DRV_CMD_ADDR], i, j);
>  			for (k = 0; k < msg->num_cmds; k++) {
> -				if (addr == msg->cmds[k].addr)
> +				/*
> +				 * Each RPMh VREG accelerator resource has 3 or 4 contiguous 4-byte
> +				 * aligned addresses associated with it. Ignore the offset to check
> +				 * for in-flight VREG requests.
> +				 */
> +				if (ACCL_TYPE(msg->cmds[k].addr) == HW_ACCL_VREG &&
> +				    VREG_ADDR(msg->cmds[k].addr) == VREG_ADDR(addr))

I'm sure this work, at least for some targets, but I don't fancy
encoding this information here. It feels like a hack.

Furthermore, I really would like TP_printk() of trace_rpmh_send_msg() to
be able to resolve the symbolic names for VRMs as well, and it would
need the same information...

Please consider how we can query command db for the type and/or grouping
information.

Regards,
Bjorn

> +					return -EBUSY;
> +				else if (addr == msg->cmds[k].addr)
>  					return -EBUSY;
>  			}
>  		}
> 
> ---
> base-commit: 943b9f0ab2cfbaea148dd6ac279957eb08b96904
> change-id: 20240117-rpmh-rsc-fixes-6c43c7051828
> 
> Best regards,
> -- 
> Maulik Shah <quic_mkshah@quicinc.com>
>