Subject: RE: [PATCH v3 2/4] net: stmmac: dwc-qos: Add FSD EQoS support

From: "Swathi K S" <[email-masked]>
Date: Thu, 6 Jun 2024 14:44:40 +0530

> -----Original Message-----
> From: Krzysztof Kozlowski [mailto:[email-masked]]
> Sent: 18 August 2023 14:57
> To: Sriranjani P <[email-masked]>; [email-masked];
> [email-masked]; [email-masked]; [email-masked];
> [email-masked]; [email-masked];
> [email-masked]; [email-masked];
> [email-masked]; [email-masked];
> [email-masked]; [email-masked]; linux-
> [email-masked]; [email-masked]; [email-masked];
> [email-masked]
> Cc: [email-masked]; [email-masked]; linux-
> [email-masked]; [email-masked]; linux-arm-
> [email-masked]; 'Chandrasekar R' <[email-masked]>;
> 'Suresh Siddha' <[email-masked]>
> 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:[email-masked]]
> >> Sent: 15 August 2023 01:21
> >> To: Sriranjani P <[email-masked]>; [email-masked];
> >> [email-masked]; [email-masked]; [email-masked];
> >> [email-masked]; [email-masked];
> >> [email-masked]; [email-masked];
> >> [email-masked]; [email-masked];
> >> [email-masked]; [email-masked]; linux-
> >> [email-masked]; [email-masked]; [email-masked];
> >> [email-masked]
> >> Cc: [email-masked]; [email-masked]; linux-
> >> [email-masked]; [email-masked]; linux-arm-
> >> [email-masked]; Chandrasekar R <[email-masked]>;
> >> Suresh Siddha <[email-masked]>
> >> 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 <[email-masked]>
> >>> Signed-off-by: Suresh Siddha <[email-masked]>
> >>> Signed-off-by: Swathi K S <[email-masked]>
> >>> Signed-off-by: Sriranjani P <[email-masked]>
> >>> ---
> >>
> >>
> >>> +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.

> Best regards,
> Krzysztof

Regards,
Swathi