linux-kernel - Re: [PATCH] soc: qcom: llcc: Fix dis_cap_alloc and retain_on

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Message-ID: <5e83d947-c77f-9318-4a4c-377a8304b8fd@quicinc.com>
Date:   Mon, 6 Nov 2023 12:24:28 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Atul Dhudase <quic_adhudase@...cinc.com>
CC:     <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <swboyd@...omium.org>,
        <isaacm@...eaurora.org>, <dianders@...omium.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] soc: qcom: llcc: Fix dis_cap_alloc and retain_on_pc
 configuration



On 11/4/2023 1:03 AM, Bjorn Andersson wrote:
> On Fri, Nov 03, 2023 at 04:27:12PM +0530, Atul Dhudase wrote:
>> While programming dis_cap_alloc and retain_on_pc, set a bit
>> corresponding to a specific SCID without disturbing the
>> previously configured bits.
>>
> 
> As far as I can see, the only invocation of _qcom_llcc_cfg_program()
> comes from qcom_llcc_cfg_program(), which is only called once, from
> qcom_llcc_probe(), and here also seems to only be the single write to
> these two registers.

It does not look to be single write but the write is for each slice
in the same register which was overriding other slices values.

-Mukesh
> 
> This implies that "the previously configured bits" would be some unknown
> configuration provided to us either from the bootloader or by reset of
> the hardware. As such this changes the value of the two registers from
> being known, to having 31 unknown bits.
> 
> 
> I'm not saying that the change is wrong, but you're altering the
> behavior of every platform except SDM845.
> As such, I want the commit message to provide an actual problem
> description, and mention the fact that you're changing the logic to
> retain the state prior to Linux.
> 
> Regards,
> Bjorn
> 
>> Fixes: c14e64b46944 ("soc: qcom: llcc: Support chipsets that can write to llcc")
>> Signed-off-by: Atul Dhudase <quic_adhudase@...cinc.com>
>> ---
>>   drivers/soc/qcom/llcc-qcom.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/soc/qcom/llcc-qcom.c b/drivers/soc/qcom/llcc-qcom.c
>> index 674abd0d6700..509d972c1bd9 100644
>> --- a/drivers/soc/qcom/llcc-qcom.c
>> +++ b/drivers/soc/qcom/llcc-qcom.c
>> @@ -941,15 +941,15 @@ static int _qcom_llcc_cfg_program(const struct llcc_slice_config *config,
>>   		u32 disable_cap_alloc, retain_pc;
>>
>>   		disable_cap_alloc = config->dis_cap_alloc << config->slice_id;
>> -		ret = regmap_write(drv_data->bcast_regmap,
>> -				LLCC_TRP_SCID_DIS_CAP_ALLOC, disable_cap_alloc);
>> +		ret = regmap_update_bits(drv_data->bcast_regmap, LLCC_TRP_SCID_DIS_CAP_ALLOC,
>> +				BIT(config->slice_id), disable_cap_alloc);
>>   		if (ret)
>>   			return ret;
>>
>>   		if (drv_data->version < LLCC_VERSION_4_1_0_0) {
>>   			retain_pc = config->retain_on_pc << config->slice_id;
>> -			ret = regmap_write(drv_data->bcast_regmap,
>> -					LLCC_TRP_PCB_ACT, retain_pc);
>> +			ret = regmap_update_bits(drv_data->bcast_regmap, LLCC_TRP_PCB_ACT,
>> +					BIT(config->slice_id), retain_pc);
>>   			if (ret)
>>   				return ret;
>>   		}
>> --
>> 2.25.1
>>