linux-kernel - Re: [PATCH 3/3] RDMA/hfi1: Use RMW accessors for changing LNKCTL2

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Message-ID: <26be3948-e687-f510-0612-abcac5d919af@linux.intel.com>
Date: Fri, 3 May 2024 13:18:35 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
cc: Alex Deucher <alexander.deucher@....com>, amd-gfx@...ts.freedesktop.org, 
    Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...il.com>, 
    Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>, 
    dri-devel@...ts.freedesktop.org, Jason Gunthorpe <jgg@...pe.ca>, 
    Leon Romanovsky <leon@...nel.org>, LKML <linux-kernel@...r.kernel.org>, 
    linux-rdma@...r.kernel.org, "Pan, Xinhui" <Xinhui.Pan@....com>, 
    Christian König <christian.koenig@....com>, 
    Lukas Wunner <lukas@...ner.de>, 
    Dean Luick <dean.luick@...nelisnetworks.com>
Subject: Re: [PATCH 3/3] RDMA/hfi1: Use RMW accessors for changing LNKCTL2

On Thu, 15 Feb 2024, Ilpo Järvinen wrote:

> Convert open coded RMW accesses for LNKCTL2 to use
> pcie_capability_clear_and_set_word() which makes its easier to
> understand what the code tries to do.
> 
> LNKCTL2 is not really owned by any driver because it is a collection of
> control bits that PCI core might need to touch. RMW accessors already
> have support for proper locking for a selected set of registers
> (LNKCTL2 is not yet among them but likely will be in the future) to
> avoid losing concurrent updates.
> 
> Suggested-by: Lukas Wunner <lukas@...ner.de>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Reviewed-by: Dean Luick <dean.luick@...nelisnetworks.com>

I found out from Linux RDMA and InfiniBand patchwork that this patch had 
been silently closed as "Not Applicable". Is there some reason for that?

I was sending this change independently out (among 2 similar ones that 
already got applied) so I wouldn't need to keep carrying it within my PCIe 
bandwidth controller series. It seemed useful enough as cleanups to stand 
on its own legs w/o requiring it to be part of PCIe bw controller series.

Should I resend the patch or do RDMA/IB maintainers prefer it to remain 
as a part of PCIe BW controller series?

-- 
 i.

> ---
>  drivers/infiniband/hw/hfi1/pcie.c | 30 ++++++++----------------------
>  1 file changed, 8 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/hfi1/pcie.c b/drivers/infiniband/hw/hfi1/pcie.c
> index 119ec2f1382b..7133964749f8 100644
> --- a/drivers/infiniband/hw/hfi1/pcie.c
> +++ b/drivers/infiniband/hw/hfi1/pcie.c
> @@ -1207,14 +1207,11 @@ int do_pcie_gen3_transition(struct hfi1_devdata *dd)
>  		    (u32)lnkctl2);
>  	/* only write to parent if target is not as high as ours */
>  	if ((lnkctl2 & PCI_EXP_LNKCTL2_TLS) < target_vector) {
> -		lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
> -		lnkctl2 |= target_vector;
> -		dd_dev_info(dd, "%s: ..new link control2: 0x%x\n", __func__,
> -			    (u32)lnkctl2);
> -		ret = pcie_capability_write_word(parent,
> -						 PCI_EXP_LNKCTL2, lnkctl2);
> +		ret = pcie_capability_clear_and_set_word(parent, PCI_EXP_LNKCTL2,
> +							 PCI_EXP_LNKCTL2_TLS,
> +							 target_vector);
>  		if (ret) {
> -			dd_dev_err(dd, "Unable to write to PCI config\n");
> +			dd_dev_err(dd, "Unable to change parent PCI target speed\n");
>  			return_error = 1;
>  			goto done;
>  		}
> @@ -1223,22 +1220,11 @@ int do_pcie_gen3_transition(struct hfi1_devdata *dd)
>  	}
>  
>  	dd_dev_info(dd, "%s: setting target link speed\n", __func__);
> -	ret = pcie_capability_read_word(dd->pcidev, PCI_EXP_LNKCTL2, &lnkctl2);
> +	ret = pcie_capability_clear_and_set_word(dd->pcidev, PCI_EXP_LNKCTL2,
> +						 PCI_EXP_LNKCTL2_TLS,
> +						 target_vector);
>  	if (ret) {
> -		dd_dev_err(dd, "Unable to read from PCI config\n");
> -		return_error = 1;
> -		goto done;
> -	}
> -
> -	dd_dev_info(dd, "%s: ..old link control2: 0x%x\n", __func__,
> -		    (u32)lnkctl2);
> -	lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
> -	lnkctl2 |= target_vector;
> -	dd_dev_info(dd, "%s: ..new link control2: 0x%x\n", __func__,
> -		    (u32)lnkctl2);
> -	ret = pcie_capability_write_word(dd->pcidev, PCI_EXP_LNKCTL2, lnkctl2);
> -	if (ret) {
> -		dd_dev_err(dd, "Unable to write to PCI config\n");
> +		dd_dev_err(dd, "Unable to change device PCI target speed\n");
>  		return_error = 1;
>  		goto done;
>  	}
>