linux-kernel - Re: [PATCH v4 2/5] soc: qcom: llcc: Add regmap for Broadcast

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Date: Tue, 2 Apr 2024 12:34:57 -0700
From: Unnathi Chalicheemala <quic_uchalich@...cinc.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Bjorn Andersson
	<andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring
	<robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>
CC: <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <kernel@...cinc.com>
Subject: Re: [PATCH v4 2/5] soc: qcom: llcc: Add regmap for Broadcast_AND
 region

On 3/30/2024 4:46 AM, Krzysztof Kozlowski wrote:
> On 29/03/2024 22:53, Unnathi Chalicheemala wrote:
>> Define new regmap structure for Broadcast_AND region and initialize
>> this regmap when HW block version is greater than 4.1, otherwise
>> initialize as a NULL pointer for backwards compatibility.
>>
> 
>> +	struct regmap *regmap;
>>  	u32 act_ctrl_reg;
>>  	u32 act_clear_reg;
>>  	u32 status_reg;
>> @@ -849,7 +850,8 @@ static int llcc_update_act_ctrl(u32 sid,
>>  		return ret;
>>  
>>  	if (drv_data->version >= LLCC_VERSION_4_1_0_0) {
>> -		ret = regmap_read_poll_timeout(drv_data->bcast_regmap, status_reg,
>> +		regmap = drv_data->bcast_and_regmap ?: drv_data->bcast_regmap;
>> +		ret = regmap_read_poll_timeout(regmap, status_reg,
>>  				      slice_status, (slice_status & ACT_COMPLETE),
>>  				      0, LLCC_STATUS_READ_DELAY);
>>  		if (ret)
>> @@ -1284,6 +1286,16 @@ static int qcom_llcc_probe(struct platform_device *pdev)
>>  
>>  	drv_data->version = version;
>>  
>> +	/* Applicable only when drv_data->version >= 4.1 */
>> +	drv_data->bcast_and_regmap = qcom_llcc_init_mmio(pdev, i + 1, "llcc_broadcast_and_base");
>> +	if (IS_ERR(drv_data->bcast_and_regmap)) {
> 
> I am pretty sure this breaks all users. Can you please explain how do
> you maintain ABI and that IS_ERR() is applied only for version >= 4.1?
> 
> Best regards,
> Krzysztof
> 
IS_ERR() check is done for all versions.
If new register isn't defined in DT(for version < 4.1) it simply sets bcast_and_regmap to NULL.
Otherwise, for version >= 4.1, it goes to err(in the case bcast_and_regmap isn't set properly).

Thank you for reviewing Krzysztof!