Re: [PATCH v4 5/6] soc: qcom: Add LLCC support for multi channel DDR

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On 28/06/2023 11:45, Komal Bajaj wrote:

No HTML emails on public mailing lists, please.

> 
> 
> On 6/23/2023 7:56 PM, Dmitry Baryshkov wrote:
>> On Fri, 23 Jun 2023 at 17:19, Komal Bajaj<quic_kbajaj@quicinc.com>  wrote:
>>> Add LLCC support for multi channel DDR configuration
>>> based on a feature register. Reading DDR channel
>>> confiuration uses nvmem framework, so select the
>>> dependency in Kconfig. Without this, there will be
>>> errors while building the driver with COMPILE_TEST only.
>>>
>>> Signed-off-by: Komal Bajaj<quic_kbajaj@quicinc.com>
>>> ---
>>>   drivers/soc/qcom/Kconfig     |  2 ++
>>>   drivers/soc/qcom/llcc-qcom.c | 33 ++++++++++++++++++++++++++++++---
>>>   2 files changed, 32 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
>>> index a491718f8064..cc9ad41c63aa 100644
>>> --- a/drivers/soc/qcom/Kconfig
>>> +++ b/drivers/soc/qcom/Kconfig
>>> @@ -64,6 +64,8 @@ config QCOM_LLCC
>>>          tristate "Qualcomm Technologies, Inc. LLCC driver"
>>>          depends on ARCH_QCOM || COMPILE_TEST
>>>          select REGMAP_MMIO
>>> +       select NVMEM
>> No need to select NVMEM. The used functions are stubbed if NVMEM is disabled
> 
> With the previous patch, where this config was not selected, below error 
> was flagged by kernel test robot -
> 
>     drivers/soc/qcom/llcc-qcom.c: In function 'qcom_llcc_get_cfg_index':
>      >> drivers/soc/qcom/llcc-qcom.c:951:15: error: implicit declaration
>     of function 'nvmem_cell_read_u8'; did you mean
>     'nvmem_cell_read_u64'? [-Werror=implicit-function-declaration]
>           951 |         ret = nvmem_cell_read_u8(&pdev->dev,
>     "multi_chan_ddr", cfg_index);
>               |               ^~~~~~~~~~~~~~~~~~
>               |               nvmem_cell_read_u64
>         cc1: some warnings being treated as errors

Judging from the rest of nvmem-consumer.h, it appears that not having 
stubs for this function is an omission. Please fix the header instead.

> 
>>> +       select QCOM_SCM
>>>          help
>>>            Qualcomm Technologies, Inc. platform specific
>>>            Last Level Cache Controller(LLCC) driver for platforms such as,
>>> diff --git a/drivers/soc/qcom/llcc-qcom.c b/drivers/soc/qcom/llcc-qcom.c
>>> index 6cf373da5df9..3c29612da1c5 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;
>>> +
>>> +       ret = nvmem_cell_read_u8(&pdev->dev, "multi-chan-ddr", cfg_index);
>>> +       if (ret == -ENOENT) {
>> || ret == -EOPNOTSUPP ?
> 
> Okay
> 
>>> +               *cfg_index = 0;
>>> +               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 +1056,19 @@ 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++)
>>> +               ;
>> Please add num_cfgs to the configuration data instead.
> 
> Shall I create a new wrapper struct having a field num_cfg and a pointer 
> to those cfgs
> because configuration data is itself an instance of "struct 
> qcom_llcc_config" and
> we can have multiple instances of it.

A wrapper struct is a better approach in my opinion.

> 
> 
>>> +       if (cfg_index >= num_entries || cfg_index < 0) {
>> cfg_index is unsigned, so it can not be less than 0.
> 
> Okay.
> 
>>> +               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)
>>> --
>>> 2.40.1
>>>
> 

-- 
With best wishes
Dmitry