linux-kernel - Re: [PATCH v2 19/22] iommu/tegra241-cmdqv: Simplify deinit flow in tegra241_cmdqv_remove

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Message-ID: <aBFNQFVbxyr596gB@google.com>
Date: Tue, 29 Apr 2025 22:05:52 +0000
From: Pranjal Shrivastava <praan@...gle.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: jgg@...dia.com, kevin.tian@...el.com, corbet@....net, will@...nel.org,
	bagasdotme@...il.com, robin.murphy@....com, joro@...tes.org,
	thierry.reding@...il.com, vdumpa@...dia.com, jonathanh@...dia.com,
	shuah@...nel.org, jsnitsel@...hat.com, nathan@...nel.org,
	peterz@...radead.org, yi.l.liu@...el.com, mshavit@...gle.com,
	zhangzekun11@...wei.com, iommu@...ts.linux.dev,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
	linux-kselftest@...r.kernel.org, patches@...ts.linux.dev,
	mochs@...dia.com, alok.a.tiwari@...cle.com, vasant.hegde@....com
Subject: Re: [PATCH v2 19/22] iommu/tegra241-cmdqv: Simplify deinit flow in
 tegra241_cmdqv_remove_vintf()

On Fri, Apr 25, 2025 at 10:58:14PM -0700, Nicolin Chen wrote:
> The current flow of tegra241_cmdqv_remove_vintf() is:
>  1. For each LVCMDQ, tegra241_vintf_remove_lvcmdq():
>     a. Disable the LVCMDQ HW
>     b. Release the LVCMDQ SW resource
>  2. For current VINTF, tegra241_vintf_hw_deinit():
>     c. Disable all LVCMDQ HWs
>     d. Disable VINTF HW
> 
> Obviously, the step 1.a and the step 2.c are redundant.
> 
> Since tegra241_vintf_hw_deinit() disables all of its LVCMDQ HWs, it could
> simplify the flow in tegra241_cmdqv_remove_vintf() by calling that first:
>  1. For current VINTF, tegra241_vintf_hw_deinit():
>     a. Disable all LVCMDQ HWs
>     b. Disable VINTF HW
>  2. Release all LVCMDQ SW resources
> 
> Drop tegra241_vintf_remove_lvcmdq(), and move tegra241_vintf_free_lvcmdq()
> as the new step 2.
> 
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> index ba029f7d24ce..8d418c131b1b 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> @@ -628,24 +628,17 @@ static int tegra241_cmdqv_init_vintf(struct tegra241_cmdqv *cmdqv, u16 max_idx,
>  
>  /* Remove Helpers */
>  
> -static void tegra241_vintf_remove_lvcmdq(struct tegra241_vintf *vintf, u16 lidx)
> -{
> -	tegra241_vcmdq_hw_deinit(vintf->lvcmdqs[lidx]);
> -	tegra241_vintf_free_lvcmdq(vintf, lidx);
> -}
> -
>  static void tegra241_cmdqv_remove_vintf(struct tegra241_cmdqv *cmdqv, u16 idx)
>  {
>  	struct tegra241_vintf *vintf = cmdqv->vintfs[idx];
>  	u16 lidx;
>  
> +	tegra241_vintf_hw_deinit(vintf);
> +
>  	/* Remove LVCMDQ resources */
>  	for (lidx = 0; lidx < vintf->cmdqv->num_lvcmdqs_per_vintf; lidx++)
>  		if (vintf->lvcmdqs[lidx])
> -			tegra241_vintf_remove_lvcmdq(vintf, lidx);
> -
> -	/* Remove VINTF resources */
> -	tegra241_vintf_hw_deinit(vintf);
> +			tegra241_vintf_free_lvcmdq(vintf, lidx);
>  
>  	dev_dbg(cmdqv->dev, "VINTF%u: deallocated\n", vintf->idx);
>  	tegra241_cmdqv_deinit_vintf(cmdqv, idx);

I don't have access to a HW spec to verify HW behaviour, but the changes
make sense to me.

Acked-by: Pranjal Shrivastava <praan@...gle.com>

> -- 
> 2.43.0
>