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

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Date: Wed, 10 Apr 2024 20:24:55 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Unnathi Chalicheemala <quic_uchalich@...cinc.com>,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Johan Hovold <johan+linaro@...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 4/2/24 21:34, Unnathi Chalicheemala wrote:
> 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).

b4 shazam <this series>

booting on 8250, I get:

[    2.794850] qcom-llcc 9200000.system-cache-controller: invalid resource (null)

which comes from lib/devres.c : __devm_ioremap_resource()

Now, this is gonna get you an angry Johan(+CC) response when he sees this land in
the next release. Perhaps, this warning could either be removed from libdevres,
or some sort of an _optional variant that doesn't print it could be introduced.

Konrad