linux-kernel - Re: [PATCH v4 08/10] PCI: brcmstb: Adjust PHY PLL setup to use a 54MHz input refclk

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Message-ID: <4bbdf9ed-f429-411b-8f5f-e51857f0f9d0@broadcom.com>
Date: Mon, 9 Dec 2024 17:52:56 -0500
From: James Quinlan <james.quinlan@...adcom.com>
To: Stanimir Varbanov <svarbanov@...e.de>, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rpi-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
 Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Florian Fainelli <florian.fainelli@...adcom.com>,
 Jim Quinlan <jim2101024@...il.com>,
 Nicolas Saenz Julienne <nsaenz@...nel.org>,
 Bjorn Helgaas <bhelgaas@...gle.com>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>, kw@...ux.com,
 Philipp Zabel <p.zabel@...gutronix.de>,
 Andrea della Porta <andrea.porta@...e.com>,
 Phil Elwell <phil@...pberrypi.com>, Jonathan Bell
 <jonathan@...pberrypi.com>, "Jim(248)Quinlan" <james.quinlan@...adcom.com>
Subject: Re: [PATCH v4 08/10] PCI: brcmstb: Adjust PHY PLL setup to use a
 54MHz input refclk

On 10/25/24 08:45, Stanimir Varbanov wrote:
> The default input reference clock for the PHY PLL is 100Mhz, except for
> some devices where it is 54Mhz like bcm2712C1 and bcm2712D0.
>
> To implement this adjustments introduce a new .post_setup op in
> pcie_cfg_data and call it at the end of brcm_pcie_setup function.
>
> The bcm2712 .post_setup callback implements the required MDIO writes that
> switch the PLL refclk and also change PHY PM clock period.
>
> Without this RPi5 PCIex1 is unable to enumerate endpoint devices on
> the expansion connector.
>
> Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>
> ---
> v3 -> v4:
>   - Improved patch description (Florian)
>
>   drivers/pci/controller/pcie-brcmstb.c | 42 +++++++++++++++++++++++++++
>   1 file changed, 42 insertions(+)
>
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index d970a76aa9ef..2571dcc14560 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -55,6 +55,10 @@
>   #define PCIE_RC_DL_MDIO_WR_DATA				0x1104
>   #define PCIE_RC_DL_MDIO_RD_DATA				0x1108
>   
> +#define PCIE_RC_PL_PHY_CTL_15				0x184c
> +#define  PCIE_RC_PL_PHY_CTL_15_DIS_PLL_PD_MASK		0x400000
> +#define  PCIE_RC_PL_PHY_CTL_15_PM_CLK_PERIOD_MASK	0xff
> +
>   #define PCIE_MISC_MISC_CTRL				0x4008
>   #define  PCIE_MISC_MISC_CTRL_PCIE_RCB_64B_MODE_MASK	0x80
>   #define  PCIE_MISC_MISC_CTRL_PCIE_RCB_MPS_MODE_MASK	0x400
> @@ -251,6 +255,7 @@ struct pcie_cfg_data {
>   	u8 num_inbound_wins;
>   	int (*perst_set)(struct brcm_pcie *pcie, u32 val);
>   	int (*bridge_sw_init_set)(struct brcm_pcie *pcie, u32 val);
> +	int (*post_setup)(struct brcm_pcie *pcie);
>   };
>   
>   struct subdev_regulators {
> @@ -826,6 +831,36 @@ static int brcm_pcie_perst_set_generic(struct brcm_pcie *pcie, u32 val)
>   	return 0;
>   }
>   
> +static int brcm_pcie_post_setup_bcm2712(struct brcm_pcie *pcie)
> +{
> +	const u16 data[] = { 0x50b9, 0xbda1, 0x0094, 0x97b4, 0x5030, 0x5030, 0x0007 };
> +	const u8 regs[] = { 0x16, 0x17, 0x18, 0x19, 0x1b, 0x1c, 0x1e };
> +	int ret, i;
> +	u32 tmp;
> +
> +	/* Allow a 54MHz (xosc) refclk source */
> +	ret = brcm_pcie_mdio_write(pcie->base, MDIO_PORT0, SET_ADDR_OFFSET, 0x1600);
> +	if (ret < 0)
> +		return ret;
> +
> +	for (i = 0; i < ARRAY_SIZE(regs); i++) {
> +		ret = brcm_pcie_mdio_write(pcie->base, MDIO_PORT0, regs[i], data[i]);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	usleep_range(100, 200);
> +
> +	/* Fix for L1SS errata */
> +	tmp = readl(pcie->base + PCIE_RC_PL_PHY_CTL_15);
> +	tmp &= ~PCIE_RC_PL_PHY_CTL_15_PM_CLK_PERIOD_MASK;
> +	/* PM clock period is 18.52ns (round down) */
> +	tmp |= 0x12;
> +	writel(tmp, pcie->base + PCIE_RC_PL_PHY_CTL_15);

Hi Stan,

Can you please say more about where this errata came from?  I asked the 
7712 PCIe HW folks and they said that there best guess was that it was a 
old workaround for a particular Broadcom Wifi endpoint.  Do you know its 
origin?

Thanks,

Jim Quinlan

Broadcom STB/CM

> +
> +	return 0;
> +}
> +
>   static void add_inbound_win(struct inbound_win *b, u8 *count, u64 size,
>   			    u64 cpu_addr, u64 pci_offset)
>   {
> @@ -1189,6 +1224,12 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
>   		PCIE_RC_CFG_VENDOR_VENDOR_SPECIFIC_REG1_ENDIAN_MODE_BAR2_MASK);
>   	writel(tmp, base + PCIE_RC_CFG_VENDOR_VENDOR_SPECIFIC_REG1);
>   
> +	if (pcie->cfg->post_setup) {
> +		ret = pcie->cfg->post_setup(pcie);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
>   	return 0;
>   }
>   
> @@ -1761,6 +1802,7 @@ static const struct pcie_cfg_data bcm2712_cfg = {
>   	.soc_base	= BCM7712,
>   	.perst_set	= brcm_pcie_perst_set_7278,
>   	.bridge_sw_init_set = brcm_pcie_bridge_sw_init_set_generic,
> +	.post_setup	= brcm_pcie_post_setup_bcm2712,
>   	.quirks		= CFG_QUIRK_AVOID_BRIDGE_SHUTDOWN,
>   	.num_inbound_wins = 10,
>   };