linux-kernel - Re: [PATCH v2 07/35] brcmfmac: pcie: Read Apple OTP information

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Message-ID: <3dfb1a06-4474-4614-08e5-b09f0977e03c@broadcom.com>
Date:   Thu, 6 Jan 2022 13:37:12 +0100
From:   Arend van Spriel <arend.vanspriel@...adcom.com>
To:     Hector Martin <marcan@...can.st>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Arend van Spriel <aspriel@...il.com>,
        Franky Lin <franky.lin@...adcom.com>,
        Hante Meuleman <hante.meuleman@...adcom.com>,
        Chi-hsien Lin <chi-hsien.lin@...ineon.com>,
        Wright Feng <wright.feng@...ineon.com>,
        Dmitry Osipenko <digetx@...il.com>
Cc:     Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Mark Kettenis <kettenis@...nbsd.org>,
        Rafał Miłecki <zajec5@...il.com>,
        Pieter-Paul Giesberts <pieter-paul.giesberts@...adcom.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hans de Goede <hdegoede@...hat.com>,
        "John W. Linville" <linville@...driver.com>,
        "brian m. carlson" <sandals@...stytoothpaste.net>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, brcm80211-dev-list.pdl@...adcom.com,
        SHA-cyfmac-dev-list@...ineon.com
Subject: Re: [PATCH v2 07/35] brcmfmac: pcie: Read Apple OTP information

On 1/4/2022 8:26 AM, Hector Martin wrote:
> On Apple platforms, the One Time Programmable ROM in the Broadcom chips
> contains information about the specific board design (module, vendor,
> version) that is required to select the correct NVRAM file. Parse this
> OTP ROM and extract the required strings.
> 
> Note that the user OTP offset/size is per-chip. This patch does not add
> any chips yet.

Reviewed-by: Arend van Spriel <arend.vanspriel@...adcom.com>
> Signed-off-by: Hector Martin <marcan@...can.st>
> ---
>   .../broadcom/brcm80211/brcmfmac/pcie.c        | 219 ++++++++++++++++++
>   include/linux/bcma/bcma_driver_chipcommon.h   |   1 +
>   2 files changed, 220 insertions(+)
> 
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
> index a52a6f8081eb..74c9a4f74813 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c

[...]

> +static int brcmf_pcie_read_otp(struct brcmf_pciedev_info *devinfo)
> +{
> +	const struct pci_dev *pdev = devinfo->pdev;
> +	struct brcmf_bus *bus = dev_get_drvdata(&pdev->dev);
> +	u32 coreid, base, words, idx, sromctl;
> +	u16 *otp;
> +	struct brcmf_core *core;
> +	int ret;
> +
> +	switch (devinfo->ci->chip) {
> +	default:
> +		/* OTP not supported on this chip */
> +		return 0;
> +	}

Does not seem this code is put to work yet. Will dive into it later on.

> +	core = brcmf_chip_get_core(devinfo->ci, coreid);
> +	if (!core) {
> +		brcmf_err(bus, "No OTP core\n");
> +		return -ENODEV;
> +	}
> +
> +	if (coreid == BCMA_CORE_CHIPCOMMON) {
> +		/* Chips with OTP accessed via ChipCommon need additional
> +		 * handling to access the OTP
> +		 */
> +		brcmf_pcie_select_core(devinfo, coreid);
> +		sromctl = READCC32(devinfo, sromcontrol);
> +
> +		if (!(sromctl & BCMA_CC_SROM_CONTROL_OTP_PRESENT)) {
> +			/* Chip lacks OTP, try without it... */
> +			brcmf_err(bus,
> +				  "OTP unavailable, using default firmware\n");
> +			return 0;
> +		}
> +
> +		/* Map OTP to shadow area */
> +		WRITECC32(devinfo, sromcontrol,
> +			  sromctl | BCMA_CC_SROM_CONTROL_OTPSEL);
> +	}
> +
> +	otp = kzalloc(sizeof(u16) * words, GFP_KERNEL);
> +
> +	/* Map bus window to SROM/OTP shadow area in core */
> +	base = brcmf_pcie_buscore_prep_addr(devinfo->pdev, base + core->base);

I guess this changes the bar window...

> +	brcmf_dbg(PCIE, "OTP data:\n");
> +	for (idx = 0; idx < words; idx++) {
> +		otp[idx] = brcmf_pcie_read_reg16(devinfo, base + 2 * idx);
> +		brcmf_dbg(PCIE, "[%8x] 0x%04x\n", base + 2 * idx, otp[idx]);
> +	}
> +
> +	if (coreid == BCMA_CORE_CHIPCOMMON) {
> +		brcmf_pcie_select_core(devinfo, coreid);

... which is why you need to reselect the core. Otherwise it makes no 
sense to me.

> +		WRITECC32(devinfo, sromcontrol, sromctl);
> +	}
> +
> +	ret = brcmf_pcie_parse_otp(devinfo, (u8 *)otp, 2 * words);
> +	kfree(otp);
> +
> +	return ret;
> +}

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