linux-kernel - Re: [PATCH v1 4/4] PCI: brcmstb: Augment driver for MIPs SOCs

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Message-ID: <20220706214200.GA224369@bhelgaas>
Date:   Wed, 6 Jul 2022 16:42:00 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jim Quinlan <jim2101024@...il.com>
Cc:     linux-pci@...r.kernel.org, linux-mips@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kevin Cernekee <cernekee@...il.com>,
        bcm-kernel-feedback-list@...adcom.com, james.quinlan@...adcom.com,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1 4/4] PCI: brcmstb: Augment driver for MIPs SOCs

On Thu, Dec 09, 2021 at 03:47:25PM -0500, Jim Quinlan wrote:
> The current brcmstb driver works for Arm and Arm64.  A few things are
> modified here for us to support MIPs as well.
> 
>   o There are four outbound range register groups and each directs a window
>     of up to 128MB.  Even though there are four 128MB DT "ranges" in the
>     bmips PCIe DT node, these ranges are contiguous and are collapsed into
>     a single range by the OF range parser.  Now the driver assumes a single
>     range -- for MIPs only -- and splits it back into 128MB sizes.
> 
>   o For bcm7425, the config space accesses must be 32-bit reads or
>     writes.  In addition, the 4k config space register array is missing
>     and not used.
> 
>   o The registers for the upper 32-bits of the outbound window address do
>     not exist.
> 
>   o Burst size must be set to 256 (this refers to an internal bus).
> ...

> @@ -118,6 +118,7 @@
>  #define PCIE_MISC_HARD_PCIE_HARD_DEBUG					0x4204
>  #define  PCIE_MISC_HARD_PCIE_HARD_DEBUG_CLKREQ_DEBUG_ENABLE_MASK	0x2
>  #define  PCIE_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK		0x08000000
> +#define  PCIE_BMIPS_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK		0x00800000

> @@ -883,7 +937,10 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
>  	pcie->bridge_sw_init_set(pcie, 0);
>  
>  	tmp = readl(base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);
> -	tmp &= ~PCIE_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK;
> +	if (is_bmips(pcie))
> +		tmp &= ~PCIE_BMIPS_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK;
> +	else
> +		tmp &= ~PCIE_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK;
>  	writel(tmp, base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);
>  	/* Wait for SerDes to be stable */
>  	usleep_range(100, 200);

brcm_pcie_resume() has similar code that updates
PCIE_MISC_HARD_PCIE_HARD_DEBUG [1]:

  tmp = readl(base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);
  u32p_replace_bits(&tmp, 0, PCIE_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK);
  writel(tmp, base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);

  /* wait for serdes to be stable */
  udelay(100);

This patch didn't change brcm_pcie_resume() to check is_bmips().
Should it?

If so, it would be nice to use the same method for updating the value
(either u32p_replace_bits or plain C bitops) in both places.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/pcie-brcmstb.c?id=v5.18#n1452