linux-kernel - Re: [PATCH v5 2/2] nvmem: sec-qfprom: Add Qualcomm secure QFPROM support

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Date:   Mon, 31 Jul 2023 09:35:57 -0700
From:   Bjorn Andersson <andersson@...nel.org>
To:     Mukesh Ojha <quic_mojha@...cinc.com>
Cc:     Komal Bajaj <quic_kbajaj@...cinc.com>, agross@...nel.org,
        konrad.dybcio@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        srinivas.kandagatla@...aro.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/2] nvmem: sec-qfprom: Add Qualcomm secure QFPROM
 support

On Thu, Jul 27, 2023 at 12:09:07PM +0530, Mukesh Ojha wrote:
> On 7/24/2023 2:08 PM, Komal Bajaj wrote:
[..]
> > diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
> > index f82431ec8aef..e248d3daadf3 100644
> > --- a/drivers/nvmem/Makefile
> > +++ b/drivers/nvmem/Makefile
> > @@ -44,6 +44,8 @@ obj-$(CONFIG_NVMEM_NINTENDO_OTP)	+= nvmem-nintendo-otp.o
> >   nvmem-nintendo-otp-y			:= nintendo-otp.o
> >   obj-$(CONFIG_NVMEM_QCOM_QFPROM)		+= nvmem_qfprom.o
> >   nvmem_qfprom-y				:= qfprom.o
> > +obj-$(CONFIG_NVMEM_QCOM_SEC_QFPROM)	+= nvmem_sec_qfprom.o
> > +nvmem_sec_qfprom-y			:= sec-qfprom.o
> 
> Are we just doing this for just renaming the object ?
> 

Correct.

> >   obj-$(CONFIG_NVMEM_RAVE_SP_EEPROM)	+= nvmem-rave-sp-eeprom.o
> >   nvmem-rave-sp-eeprom-y			:= rave-sp-eeprom.o
> >   obj-$(CONFIG_NVMEM_RMEM) 		+= nvmem-rmem.o
> > diff --git a/drivers/nvmem/sec-qfprom.c b/drivers/nvmem/sec-qfprom.c
[..]
> > +static int sec_qfprom_reg_read(void *context, unsigned int reg, void *_val, size_t bytes)
> > +{
> > +	struct sec_qfprom *priv = context;
> > +	unsigned int i;
> > +	u8 *val = _val;
> > +	u32 read_val;
> > +	u8 *tmp;
> > +
> > +	for (i = 0; i < bytes; i++, reg++) {
> > +		if (i == 0 || reg % 4 == 0) {
> > +			if (qcom_scm_io_readl(priv->base + (reg & ~3), &read_val)) {
> > +				dev_err(priv->dev, "Couldn't access fuse register\n");
> > +				return -EINVAL;
> > +			}
> > +			tmp = (u8 *)&read_val;
> > +		}
> > +
> > +		val[i] = tmp[reg & 3];
> > +	}
> 
> Getting secure read from fuse region is fine here, since we have to read
> 4 byte from trustzone, but this restriction of reading is also there
> for sm8{4|5}50 soc's where byte by byte reading is protected and granularity
> set to 4 byte (qfprom_reg_read() in drivers/nvmem/qfprom.c)
> is will result in abort, in  that case this function need to export this
> logic.
> 

If qfprom needs similar treatment, then let's land this first and then
consider generalizing (i.e. move to some library code) this - or if
infeasible, just fix qfprom_reg_read().

Regards,
Bjorn