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

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Date:   Wed, 14 Jun 2023 12:00:41 +0530
From:   Komal Bajaj <quic_kbajaj@...cinc.com>
To:     Bjorn Andersson <andersson@...nel.org>
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 6/13/2023 10:41 PM, Bjorn Andersson wrote:
> 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.

Noted.

>
>> +
>> +	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?

No, if nvmem_cell_read_u8() fails with any error, cfg_index will not be 
changed.

Thanks
Komal
>> +		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
>>