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Date: Thu, 6 Jun 2024 14:16:55 +0200
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Subject: Re: [PATCH v3 2/4] net: stmmac: dwc-qos: Add FSD EQoS support
To: Swathi K S <swathi.ks@samsung.com>, davem@davemloft.net,
 edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, robh+dt@kernel.org,
 krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
 richardcochran@gmail.com, alexandre.torgue@foss.st.com,
 joabreu@synopsys.com, mcoquelin.stm32@gmail.com, alim.akhtar@samsung.com,
 linux-fsd@tesla.com, pankaj.dubey@samsung.com, ravi.patel@samsung.com
Cc: netdev@vger.kernel.org, devicetree@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
 linux-arm-kernel@lists.infradead.org, 'Chandrasekar R'
 <rcsekar@samsung.com>, 'Suresh Siddha' <ssiddha@tesla.com>
References: <20230814112539.70453-1-sriranjani.p@samsung.com>
 <CGME20230814112612epcas5p275cffb4d3dae86c6090ca246083631c4@epcas5p2.samsung.com>
 <20230814112539.70453-3-sriranjani.p@samsung.com>
 <b224ccaf-d70f-8f65-4b2f-6f4798841558@linaro.org>
 <001201d9d00c$5413a9a0$fc3afce0$@samsung.com>
 <baa64cff-885a-2ecb-8a0f-3b820e55e1b8@linaro.org>
 <000101dab7f2$1aa41320$4fec3960$@samsung.com>
From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
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On 06/06/2024 11:14, Swathi K S wrote:
> 
> 
>> -----Original Message-----
>> From: Krzysztof Kozlowski [mailto:krzysztof.kozlowski@linaro.org]
>> Sent: 18 August 2023 14:57
>> To: Sriranjani P <sriranjani.p@samsung.com>; davem@davemloft.net;
>> edumazet@google.com; kuba@kernel.org; pabeni@redhat.com;
>> robh+dt@kernel.org; krzysztof.kozlowski+dt@linaro.org;
>> conor+dt@kernel.org; richardcochran@gmail.com;
>> alexandre.torgue@foss.st.com; joabreu@synopsys.com;
>> mcoquelin.stm32@gmail.com; alim.akhtar@samsung.com; linux-
>> fsd@tesla.com; pankaj.dubey@samsung.com; swathi.ks@samsung.com;
>> ravi.patel@samsung.com
>> Cc: netdev@vger.kernel.org; devicetree@vger.kernel.org; linux-
>> kernel@vger.kernel.org; linux-samsung-soc@vger.kernel.org; linux-arm-
>> kernel@lists.infradead.org; 'Chandrasekar R' <rcsekar@samsung.com>;
>> 'Suresh Siddha' <ssiddha@tesla.com>
>> Subject: Re: [PATCH v3 2/4] net: stmmac: dwc-qos: Add FSD EQoS support
>>
>> On 16/08/2023 08:38, Sriranjani P wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: Krzysztof Kozlowski [mailto:krzysztof.kozlowski@linaro.org]
>>>> Sent: 15 August 2023 01:21
>>>> To: Sriranjani P <sriranjani.p@samsung.com>; davem@davemloft.net;
>>>> edumazet@google.com; kuba@kernel.org; pabeni@redhat.com;
>>>> robh+dt@kernel.org; krzysztof.kozlowski+dt@linaro.org;
>>>> conor+dt@kernel.org; richardcochran@gmail.com;
>>>> alexandre.torgue@foss.st.com; joabreu@synopsys.com;
>>>> mcoquelin.stm32@gmail.com; alim.akhtar@samsung.com; linux-
>>>> fsd@tesla.com; pankaj.dubey@samsung.com; swathi.ks@samsung.com;
>>>> ravi.patel@samsung.com
>>>> Cc: netdev@vger.kernel.org; devicetree@vger.kernel.org; linux-
>>>> kernel@vger.kernel.org; linux-samsung-soc@vger.kernel.org; linux-arm-
>>>> kernel@lists.infradead.org; Chandrasekar R <rcsekar@samsung.com>;
>>>> Suresh Siddha <ssiddha@tesla.com>
>>>> Subject: Re: [PATCH v3 2/4] net: stmmac: dwc-qos: Add FSD EQoS
>>>> support
>>>>
>>>> On 14/08/2023 13:25, Sriranjani P wrote:
>>>>> The FSD SoC contains two instance of the Synopsys DWC ethernet QOS
>>>>> IP
>>>> core.
>>>>> The binding that it uses is slightly different from existing ones
>>>>> because of the integration (clocks, resets).
>>>>>
>>>>> For FSD SoC, a mux switch is needed between internal and external
>> clocks.
>>>>> By default after reset internal clock is used but for receiving
>>>>> packets properly, external clock is needed. Mux switch to external
>>>>> clock happens only when the external clock is present.
>>>>>
>>>>> Signed-off-by: Chandrasekar R <rcsekar@samsung.com>
>>>>> Signed-off-by: Suresh Siddha <ssiddha@tesla.com>
>>>>> Signed-off-by: Swathi K S <swathi.ks@samsung.com>
>>>>> Signed-off-by: Sriranjani P <sriranjani.p@samsung.com>
>>>>> ---
>>>>
>>>>
>>>>> +static int dwc_eqos_setup_rxclock(struct platform_device *pdev, int
>>>>> +ins_num) {
>>>>> +	struct device_node *np = pdev->dev.of_node;
>>>>> +	struct regmap *syscon;
>>>>> +	unsigned int reg;
>>>>> +
>>>>> +	if (np && of_property_read_bool(np, "fsd-rx-clock-skew")) {
>>>>> +		syscon = syscon_regmap_lookup_by_phandle_args(np,
>>>>> +							      "fsd-rx-clock-
>>>> skew",
>>>>> +							      1, &reg);
>>>>> +		if (IS_ERR(syscon)) {
>>>>> +			dev_err(&pdev->dev,
>>>>> +				"couldn't get the rx-clock-skew syscon!\n");
>>>>> +			return PTR_ERR(syscon);
>>>>> +		}
>>>>> +
>>>>> +		regmap_write(syscon, reg, rx_clock_skew_val[ins_num]);
>>>>> +	}
>>>>> +
>>>>> +	return 0;
>>>>> +}
>>>>> +
>>>>> +static int fsd_eqos_clk_init(struct fsd_eqos_plat_data *plat,
>>>>> +			     struct plat_stmmacenet_data *data) {
>>>>> +	int ret = 0, i;
>>>>> +
>>>>> +	const struct fsd_eqos_variant *fsd_eqos_v_data =
>>>>> +						plat->fsd_eqos_inst_var;
>>>>> +
>>>>> +	plat->clks = devm_kcalloc(plat->dev, fsd_eqos_v_data->num_clks,
>>>>> +				  sizeof(*plat->clks), GFP_KERNEL);
>>>>> +	if (!plat->clks)
>>>>> +		return -ENOMEM;
>>>>> +
>>>>> +	for (i = 0; i < fsd_eqos_v_data->num_clks; i++)
>>>>> +		plat->clks[i].id = fsd_eqos_v_data->clk_list[i];
>>>>> +
>>>>> +	ret = devm_clk_bulk_get(plat->dev, fsd_eqos_v_data->num_clks,
>>>>> +				plat->clks);
>>>>
>>>> Instead of duplicating entire clock management with existing code,
>>>> you should extend/rework existing one.
>>>>
>>>> This code is unfortunately great example how not to stuff vendor code
>>>> into upstream project. :(
>>>
>>> I will check again if I can extend existing one to support FSD platform
>> specific requirement.
>>>
>>>>
>>>>> +
>>>>> +	return ret;
>>>>> +}
>>>>> +
>>>>> +static int fsd_clks_endisable(void *priv, bool enabled) {
>>>>> +	int ret, num_clks;
>>>>> +	struct fsd_eqos_plat_data *plat = priv;
>>>>> +
>>>>> +	num_clks = plat->fsd_eqos_inst_var->num_clks;
>>>>> +
>>>>> +	if (enabled) {
>>>>> +		ret = clk_bulk_prepare_enable(num_clks, plat->clks);
>>>>> +		if (ret) {
>>>>> +			dev_err(plat->dev, "Clock enable failed, err = %d\n",
>>>> ret);
>>>>> +			return ret;
>>>>> +		}
>>>>> +	} else {
>>>>> +		clk_bulk_disable_unprepare(num_clks, plat->clks);
>>>>> +	}
>>>>> +
>>>>> +	return 0;
>>>>> +}
>>>>> +
>>>>> +static int fsd_eqos_probe(struct platform_device *pdev,
>>>>> +			  struct plat_stmmacenet_data *data,
>>>>> +			  struct stmmac_resources *res)
>>>>> +{
>>>>> +	struct fsd_eqos_plat_data *priv_plat;
>>>>> +	struct device_node *np = pdev->dev.of_node;
>>>>> +	int ret = 0;
>>>>> +
>>>>> +	priv_plat = devm_kzalloc(&pdev->dev, sizeof(*priv_plat),
>>>> GFP_KERNEL);
>>>>> +	if (!priv_plat) {
>>>>> +		ret = -ENOMEM;
>>>>
>>>> return -ENOMEM
>>>
>>> Will fix this in v4.
>>>
>>>>
>>>>> +		goto error;
>>>>> +	}
>>>>> +
>>>>> +	priv_plat->dev = &pdev->dev;
>>>>> +	data->bus_id = of_alias_get_id(np, "eth");
>>>>
>>>> No, you cannot do like this. Aliases are board specific and are based
>>>> on labeling on the board.
>>>
>>> So if I understood this correctly, I need to move alias in the board
>>> specific DTS file
>>
>> This part: yes
>>
>>> and I can use this, because we have to handle rx-clock-skew differently for
>> the two instances in the FSD platform.
>>
>> Not really. Do you expect it to work correctly if given EQoS instance receives
>> different alias, e.g. 5?
>>
>>> Another approach we took in v1, by specifying the value to be programmed
>> in rx-clock-skew property itself, but it seems it is not a preferred approach.
>>> I can see that in drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>> +436 common code is already using this API and getting alias id, so I can
>> probably use the same rather getting same again here, but I have to specify
>> alias in DTS file.
>>
>> Getting alias ID is okay in general. It is used to provide user-visible ID of the
>> devices (see mmc). Using such alias to configure hardware is abuse of the
>> alias, because of the reasons I said - how is it supposed to work if alias is 5
>> (this is perfectly valid alias)?
>>
>> I suspect that all this is to substitute missing abstractions, like clocks, phys or
>> resets...
> 
> Will avoid using the API to get alias id to configure the HW. Will share the new implementation in v4.

That was August 2023, almost year ago.

Whatever you plan, expect having same questions in the discussion
because we forgot everything said that year ago...

Best regards,
Krzysztof