netdev - Re: [PATCH v3 02/11] net: stmmac: dwmac-stm32: Separate out external clock rate validation

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Date: Mon, 3 Jun 2024 16:27:06 +0200
From: Marek Vasut <marex@...x.de>
To: Christophe Roullier <christophe.roullier@...s.st.com>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Richard Cochran <richardcochran@...il.com>, Jose Abreu
 <joabreu@...opsys.com>, Liam Girdwood <lgirdwood@...il.com>,
 Mark Brown <broonie@...nel.org>, Sai Krishna Gajula <saikrishnag@...vell.com>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 02/11] net: stmmac: dwmac-stm32: Separate out external
 clock rate validation

On 6/3/24 11:27 AM, Christophe Roullier wrote:
> From: Marek Vasut <marex@...x.de>
> 
> Pull the external clock frequency validation into a separate function,
> to avoid conflating it with external clock DT property decoding and
> clock mux register configuration. This should make the code easier to
> read and understand.
> 
> This does change the code behavior slightly. The clock mux PMCR register
> setting now depends solely on the DT properties which configure the clock
> mux between external clock and internal RCC generated clock. The mux PMCR
> register settings no longer depend on the supplied clock frequency, that
> supplied clock frequency is now only validated, and if the clock frequency
> is invalid for a mode, it is rejected.
> 
> Previously, the code would switch the PMCR register clock mux to internal
> RCC generated clock if external clock couldn't provide suitable frequency,
> without checking whether the RCC generated clock frequency is correct. Such
> behavior is risky at best, user should have configured their clock correctly
> in the first place, so this behavior is removed here.
> 
> Signed-off-by: Marek Vasut <marex@...x.de>
> ---
>   .../net/ethernet/stmicro/stmmac/dwmac-stm32.c | 54 +++++++++++++++----
>   1 file changed, 44 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
> index c92dfc4ecf570..43340a5573c64 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
> @@ -157,25 +157,57 @@ static int stm32_dwmac_init(struct plat_stmmacenet_data *plat_dat, bool resume)
>   	return stm32_dwmac_clk_enable(dwmac, resume);
>   }
>   
> +static int stm32mp1_validate_ethck_rate(struct plat_stmmacenet_data *plat_dat)
> +{
> +	struct stm32_dwmac *dwmac = plat_dat->bsp_priv;
> +	const u32 clk_rate = clk_get_rate(dwmac->clk_eth_ck);

 From Sai in
Re: [net-next,RFC,PATCH 1/5] net: stmmac: dwmac-stm32: Separate out 
external clock rate validation

Please check reverse x-mass tree is followed for these variables, if 
possible.

> +	switch (plat_dat->mac_interface) {
> +	case PHY_INTERFACE_MODE_MII:
> +		if (clk_rate == ETH_CK_F_25M)
> +			return 0;
> +		break;
> +	case PHY_INTERFACE_MODE_GMII:
> +		if (clk_rate == ETH_CK_F_25M)
> +			return 0;
> +		break;

 From Sai in
Re: [net-next,RFC,PATCH 1/5] net: stmmac: dwmac-stm32: Separate out 
external clock rate validation

Please check, whether we can combine the two cases..

> +	case PHY_INTERFACE_MODE_RMII:
> +		if (clk_rate == ETH_CK_F_25M || clk_rate == ETH_CK_F_50M)
> +			return 0;
> +		break;
> +	case PHY_INTERFACE_MODE_RGMII:
> +	case PHY_INTERFACE_MODE_RGMII_ID:
> +	case PHY_INTERFACE_MODE_RGMII_RXID:
> +	case PHY_INTERFACE_MODE_RGMII_TXID:
> +		if (clk_rate == ETH_CK_F_25M || clk_rate == ETH_CK_F_125M)
> +			return 0;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	dev_err(dwmac->dev, "Mode %s does not match eth-ck frequency %d Hz",
> +		phy_modes(plat_dat->mac_interface), clk_rate);
> +	return -EINVAL;
> +}

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