linux-kernel - Re: [PATCH v2 1/2] nvmem: qfprom: Ensure access to qfprom is word aligned

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Message-ID: <60068361-ddb7-4906-84ca-195e5eb13a0f@linaro.org>
Date: Mon, 9 Dec 2024 09:55:14 +0000
From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Naman Jain <quic_namajain@...cinc.com>
Subject: Re: [PATCH v2 1/2] nvmem: qfprom: Ensure access to qfprom is word
 aligned



On 26/10/2024 23:42, Dmitry Baryshkov wrote:
> From: Naman Jain <quic_namajain@...cinc.com>
> 
> Add logic for alignment of address for reading in qfprom driver to avoid
> NOC error issues due to unaligned access. The problem manifests on the
> SAR2130P platform, but in msm-5.x kernels the fix is applied

Is this only issue with SAR2130P?

> uncoditionally. Follow this approach and uncoditionally perform aligned
> reads.

If there is a need of having proper register alignment this should go as 
part of the nvmem_config->stride and word_size configuration and not in 
reg_read callbacks.


--srini

> 
> Fixes: 4ab11996b489 ("nvmem: qfprom: Add Qualcomm QFPROM support.")
> Signed-off-by: Naman Jain <quic_namajain@...cinc.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>   drivers/nvmem/qfprom.c | 19 ++++++++++++++++---
>   1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
> index 116a39e804c70b4a0374f8ea3ac6ba1dd612109d..cad319e7bfcf34c9b9ab15eb331efda822699cce 100644
> --- a/drivers/nvmem/qfprom.c
> +++ b/drivers/nvmem/qfprom.c
> @@ -322,15 +322,28 @@ static int qfprom_reg_read(void *context,
>   {
>   	struct qfprom_priv *priv = context;
>   	u8 *val = _val;
> -	int i = 0, words = bytes;
> +	int buf_start, buf_end, index, i = 0;
>   	void __iomem *base = priv->qfpcorrected;
> +	char *buffer = NULL;
> +	u32 read_val;
>   
>   	if (read_raw_data && priv->qfpraw)
>   		base = priv->qfpraw;
> +	buf_start = ALIGN_DOWN(reg, 4);
> +	buf_end = ALIGN(reg + bytes, 4);
> +	buffer = kzalloc(buf_end - buf_start, GFP_KERNEL);
> +	if (!buffer) {
> +		pr_err("memory allocation failed in %s\n", __func__);
> +		return -ENOMEM;
> +	}
>   
> -	while (words--)
> -		*val++ = readb(base + reg + i++);
> +	for (index = buf_start; index < buf_end; index += 4, i += 4) {
> +		read_val = readl_relaxed(base + index);
> +		memcpy(buffer + i, &read_val, 4);
> +	}
>   
> +	memcpy(val, buffer + reg % 4, bytes);
> +	kfree(buffer);
>   	return 0;
>   }
>   
>