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

[Komal Bajaj]

On 6/28/2023 4:43 PM, Konrad Dybcio wrote:
> On 28.06.2023 10:52, Komal Bajaj wrote:
> > On 6/23/2023 8:28 PM, Konrad Dybcio wrote:
> > > On 23.06.2023 16:18, Komal Bajaj 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@xxxxxxxxxxx>
> > > > ---
> > > >    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
> > > > +    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) {
> > > > +        *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++)
> > > > +        ;
> > > > +    if (cfg_index >= num_entries || cfg_index < 0) {
> > > cfg_index is an unsigned variable, it can never be < 0
> > Okay, will remove this condition.
> >
> > > > +        ret = -EINVAL;
> > > > +        goto err;
> > > > +    }
> > > > +
> > > if (cfg_index >= entry->size)? With that, you can also keep the config
> > > entries non-0-terminated in the previous patch, saving a whole lot of RAM.
> > entry->size represents the size of sct table whereas num_entries represents the number
> > of sct tables that we can have. And by this check we are validating the value read from the
> > fuse register. Am I understanding your comment correctly?
> Oh you're right.
>
> I still see room for improvement, though.
>
> For example, you duplicate assigning need_llcc_cfg, reg_offset
> and edac_reg_offset. You can add a new struct, like "sct_config" and add
> a pointer to sct_config[] & the length of this array to qcom_llcc_config.
>
> Konrad

Okay, will follow this approach.

> > > Konrad
> > > > +    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)