netdev - Re: [PATCH v5 4/7] r8169: Coalesce mac ocp write and modify for 8168ep start to reduce spinlock contention

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Date: Mon, 30 Oct 2023 14:51:19 +0100
From: Heiner Kallweit <hkallweit1@...il.com>
To: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>,
 Jason Gunthorpe <jgg@...pe.ca>, Joerg Roedel <jroedel@...e.de>,
 Lu Baolu <baolu.lu@...ux.intel.com>, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>, nic_swsd@...ltek.com,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Marco Elver <elver@...gle.com>
Subject: Re: [PATCH v5 4/7] r8169: Coalesce mac ocp write and modify for
 8168ep start to reduce spinlock contention

On 29.10.2023 19:36, Mirsad Goran Todorovac wrote:
> Repeated calls to r8168_mac_ocp_write() and r8168_mac_ocp_modify() in
> the startup of RTL8168ep involve implicit spin_lock_irqsave() and
> spin_unlock_irqrestore() on each invocation.
> 
> Coalesced with the corresponding helpers into r8168_mac_ocp_write_seq() and
> r8168_mac_ocp_modify_seq() with a sinqle paired spin_lock_irqsave() and
> spin_unlock_irqrestore(), these calls help reduce overall spinlock contention.
> 
> Fixes: ef712ede3541d ("r8169: add helper r8168_mac_ocp_modify")
> Cc: Heiner Kallweit <hkallweit1@...il.com>
> Cc: Marco Elver <elver@...gle.com>
> Cc: nic_swsd@...ltek.com
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: netdev@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Link: https://lore.kernel.org/lkml/20231028005153.2180411-1-mirsad.todorovac@alu.unizg.hr/
> Link: https://lore.kernel.org/lkml/20231028110459.2644926-1-mirsad.todorovac@alu.unizg.hr/
> Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
> ---
> v5:
>  added unlocked primitives to allow mac ocs modify grouping
>  applied coalescing of mac ocp writes/modifies for 8168ep and 8117
>  some formatting fixes to please checkpatch.pl
> 
> v4:
>  fixed complaints as advised by Heiner and checkpatch.pl
>  split the patch into five sections to be more easily manipulated and reviewed
>  introduced r8168_mac_ocp_write_seq()
>  applied coalescing of mac ocp writes/modifies for 8168H, 8125 and 8125B
> 
> v3:
>  removed register/mask pair array sentinels, so using ARRAY_SIZE().
>  avoided duplication of RTL_W32() call code as advised by Heiner.
> 
>  drivers/net/ethernet/realtek/r8169_main.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index 29ee93b8b702..27016aaeb6a0 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -3326,6 +3326,12 @@ static void rtl_hw_start_8168ep_3(struct rtl8169_private *tp)
>  		{ 0x1e, 0x0000,	0x2000 },
>  	};
>  
> +	static const struct e_info_regmaskset e_info_8168ep_3_mod_1[] = {
> +		{ 0xd3e2, 0x0fff, 0x0271 },
> +		{ 0xd3e4, 0x00ff, 0x0000 },
> +		{ 0xe860, 0x0000, 0x0080 },
> +	};
> +
>  	rtl_ephy_init(tp, e_info_8168ep_3);
>  
>  	rtl_hw_start_8168ep(tp);
> @@ -3333,9 +3339,7 @@ static void rtl_hw_start_8168ep_3(struct rtl8169_private *tp)
>  	RTL_W8(tp, DLLPR, RTL_R8(tp, DLLPR) & ~PFM_EN);
>  	RTL_W8(tp, MISC_1, RTL_R8(tp, MISC_1) & ~PFM_D3COLD_EN);
>  
> -	r8168_mac_ocp_modify(tp, 0xd3e2, 0x0fff, 0x0271);
> -	r8168_mac_ocp_modify(tp, 0xd3e4, 0x00ff, 0x0000);
> -	r8168_mac_ocp_modify(tp, 0xe860, 0x0000, 0x0080);
> +	r8168_mac_ocp_modify_seq(tp, e_info_8168ep_3_mod_1);
>  }
>  
>  static void rtl_hw_start_8117(struct rtl8169_private *tp)

Same here, it' not worth it and makes the code harder to read.