linux-kernel - Re: [PATCH 4/6] mips: bmips: setup: make CBR address configurable

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Date: Fri, 3 May 2024 12:09:02 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Christian Marangi <ansuelsmth@...il.com>,
 Hauke Mehrtens <hauke@...ke-m.de>, Rafał Miłecki
 <zajec5@...il.com>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>,
 Álvaro Fernández Rojas <noltari@...il.com>,
 linux-mips@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Daniel González Cabanelas
 <dgcbueu@...il.com>
Subject: Re: [PATCH 4/6] mips: bmips: setup: make CBR address configurable

On 5/3/24 06:54, Christian Marangi wrote:
> Add support to provide CBR address from DT to handle broken
> SoC/Bootloader that doesn't correctly init it. This permits to use the
> RAC flush even in these condition.
> 
> To provide a CBR address from DT, the property "mips-cbr-reg" needs to
> be set in the "cpus" node. On DT init, this property presence will be
> checked and will set the bmips_cbr_addr value accordingly. Also
> bmips_rac_flush_disable will be set to false as RAC flush can be
> correctly supported.
> 
> The CBR address from DT will be applied only if the CBR address from the
> registers is 0, if the CBR address from the registers is not 0 and
> is not equal to the one set in DT (if provided) a WARN is printed.
> 
> To ALWAYS overwrite the CBR address the additional property
> "mips-broken-cbr-reg" needs to be set.
> 
> Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
> ---
>   arch/mips/bmips/setup.c | 30 +++++++++++++++++++++++++++---
>   1 file changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/mips/bmips/setup.c b/arch/mips/bmips/setup.c
> index 18561d426f89..bef84677248e 100644
> --- a/arch/mips/bmips/setup.c
> +++ b/arch/mips/bmips/setup.c
> @@ -34,7 +34,11 @@
>   #define REG_BCM6328_OTP		((void __iomem *)CKSEG1ADDR(0x1000062c))
>   #define BCM6328_TP1_DISABLED	BIT(9)
>   
> -/* CBR addr doesn't change and we can cache it */
> +/*
> + * CBR addr doesn't change and we can cache it.
> + * For broken SoC/Bootloader CBR addr might also be provided via DT
> + * with "mips-cbr-reg" in the "cpus" node.
> + */
>   void __iomem *bmips_cbr_addr;
>   extern bool bmips_rac_flush_disable;
>   
> @@ -212,8 +216,28 @@ void __init device_tree_init(void)
>   
>   	/* Disable SMP boot unless both CPUs are listed in DT and !disabled */
>   	np = of_find_node_by_name(NULL, "cpus");
> -	if (np && of_get_available_child_count(np) <= 1)
> -		bmips_smp_enabled = 0;
> +	if (np) {

Please reduce the indentation with early return/gotos. There might also 
be a need to do some validation that the CBR is at least outside of the 
DRAM window, that is we cannot blindly trust the DT to have gotten the 
CBR right IMHO.
-- 
Florian


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