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SubjectRe: [Patch v1 01/10] memory: tegra: add interconnect support for DRAM scaling in Tegra234
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On 21/12/22 22:13, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 21.12.2022 12:35, Sumit Gupta пишет:
>>
>>
>> On 20/12/22 23:40, Dmitry Osipenko wrote:
>>> External email: Use caution opening links or attachments
>>>
>>>
>>> 20.12.2022 19:02, Sumit Gupta пишет:
>>>> +static int tegra_emc_icc_get_init_bw(struct icc_node *node, u32
>>>> *avg, u32 *peak)
>>>> +{
>>>> + *avg = 0;
>>>> + *peak = 0;
>>>> +
>>>> + return 0;
>>>> +}
>>>
>>> Looks wrong, you should add ICC support to all the drivers first and
>>> only then enable ICC. I think you added this init_bw() to work around
>>> the fact that ICC isn't supported by T234 drivers.
>>
>> If get_bw hook is not added then max freq is set due to 'INT_MAX' below.
>>
>> void icc_node_add(struct icc_node *node, struct icc_provider *provider)
>> {
>> ....
>> /* get the initial bandwidth values and sync them with hardware */
>> if (provider->get_bw) {
>> provider->get_bw(node, &node->init_avg, &node->init_peak);
>> } else {
>> node->init_avg = INT_MAX;
>> node->init_peak = INT_MAX;
>> }
>>
>> So, will have to add the empty functions at least.
>>
>> static int tegra_emc_icc_get_init_bw(struct icc_node *node, u32 *avg,
>> u32 *peak)
>> {
>> - *avg = 0;
>> - *peak = 0;
>> -
>> return 0;
>> }
>>
>> Support to all the client drivers can't be added at once as there are
>> many drivers all with different requirements and handling. This patch
>> series is the beginning to add the basic interconnect support in new
>> Tegra SoC's. Support for more clients will be added later one by one or
>> in batch.
>
> This means that bandwidth management isn't working properly. You should
> leave the freq to INT_MAX and fix the missing integer overflows in the
> code if any, or read out the BW from FW.
>
> Once you'll enable ICC for all drivers, it will start working.
>

Referred the below patches and now understand what you mean.

https://patchwork.kernel.org/project/linux-arm-msm/cover/20200825170152.6434-1-georgi.djakov@linaro.org/
https://lore.kernel.org/all/20210912183009.6400-1-digetx@gmail.com/

There is no MRQ currently in BPMP-FW to get the bandwidth for a client.
So, can't add that in get_bw(). As explained earlier, we are in process
adding of adding support for all clients but that may take some time. We
can remove the get_bw() calls initializing "*bw = 0" once we have the
support added in all clients. Noticed that below drivers also do same.

$ grep -rB3 "*peak = 0" drivers/interconnect/*
drivers/interconnect/imx/imx.c-static int imx_icc_get_bw(struct
icc_node *node, u32 *avg, u32 *peak)
drivers/interconnect/imx/imx.c-{
drivers/interconnect/imx/imx.c- *avg = 0;
drivers/interconnect/imx/imx.c: *peak = 0;
--
drivers/interconnect/qcom/msm8974.c-static int msm8974_get_bw(struct
icc_node *node, u32 *avg, u32 *peak)
drivers/interconnect/qcom/msm8974.c-{
drivers/interconnect/qcom/msm8974.c- *avg = 0;
drivers/interconnect/qcom/msm8974.c: *peak = 0;

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