linux-kernel - Re: [PATCH v3 06/10] soc: qcom: Add LLCC support for multi channel DDR

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Date:   Tue, 13 Jun 2023 10:11:10 -0700
From:   Bjorn Andersson <andersson@...nel.org>
To:     Komal Bajaj <quic_kbajaj@...cinc.com>
Cc:     Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3 06/10] soc: qcom: Add LLCC support for multi channel
 DDR

On Fri, May 12, 2023 at 05:51:30PM +0530, Komal Bajaj wrote:
> Add LLCC support for multi channel DDR configuration
> based on a feature register.
> 
> Signed-off-by: Komal Bajaj <quic_kbajaj@...cinc.com>
> ---
>  drivers/soc/qcom/llcc-qcom.c | 32 +++++++++++++++++++++++++++++---
>  1 file changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/soc/qcom/llcc-qcom.c b/drivers/soc/qcom/llcc-qcom.c
> index 6cf373da5df9..1da337e7a378 100644
> --- a/drivers/soc/qcom/llcc-qcom.c
> +++ b/drivers/soc/qcom/llcc-qcom.c
> @@ -12,6 +12,7 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
> +#include <linux/nvmem-consumer.h>
>  #include <linux/of.h>
>  #include <linux/of_device.h>
>  #include <linux/regmap.h>
> @@ -943,6 +944,19 @@ static int qcom_llcc_cfg_program(struct platform_device *pdev,
>  	return ret;
>  }
> 
> +static int qcom_llcc_get_cfg_index(struct platform_device *pdev, u8 *cfg_index)
> +{
> +	int ret = 0;

First use is an assignment, no need to initialize here.

> +
> +	ret = nvmem_cell_read_u8(&pdev->dev, "multi_chan_ddr", cfg_index);
> +	if (ret == -ENOENT) {
> +		*cfg_index = 0;

Does nvmem_cell_read_u8() cahnge cfg_index when it fails with -ENOENT?

> +		return 0;
> +	}
> +
> +	return ret;
> +}
> +
>  static int qcom_llcc_remove(struct platform_device *pdev)
>  {
>  	/* Set the global pointer to a error code to avoid referencing it */
> @@ -975,11 +989,13 @@ static int qcom_llcc_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	int ret, i;
>  	struct platform_device *llcc_edac;
> -	const struct qcom_llcc_config *cfg;
> +	const struct qcom_llcc_config *cfg, *entry;
>  	const struct llcc_slice_config *llcc_cfg;
>  	u32 sz;
> +	u8 cfg_index;
>  	u32 version;
>  	struct regmap *regmap;
> +	u32 num_entries = 0;
> 
>  	drv_data = devm_kzalloc(dev, sizeof(*drv_data), GFP_KERNEL);
>  	if (!drv_data) {
> @@ -1040,8 +1056,18 @@ static int qcom_llcc_probe(struct platform_device *pdev)
> 
>  	drv_data->version = version;
> 
> -	llcc_cfg = cfg[0]->sct_data;
> -	sz = cfg[0]->size;
> +	ret = qcom_llcc_get_cfg_index(pdev, &cfg_index);
> +	if (ret)
> +		goto err;
> +
> +	for (entry = cfg; entry->sct_data; entry++, num_entries++);

This is not readable, move the increment of num_entries out of there.

> +	if (cfg_index >= num_entries || cfg_index < 0) {

How can cfg_index be negative?

Regards,
Bjorn

> +		ret = -EINVAL;
> +		goto err;
> +	}
> +
> +	llcc_cfg = cfg[cfg_index].sct_data;
> +	sz = cfg[cfg_index].size;
> 
>  	for (i = 0; i < sz; i++)
>  		if (llcc_cfg[i].slice_id > drv_data->max_slices)
> --
> 2.17.1
>