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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Yixun Lan , Maxime Coquelin , Alexandre Torgue , Richard Cochran , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , "Russell King (Oracle)" , Yao Zi , Yanteng Si , Lad Prabhakar , Maxime Chevallier , Choong Yong Liang , Chen-Yu Tsai , Shangjuan Wei , Boon Khai Ng , Quentin Schulz , Giuseppe Cavallaro , Jose Abreu Cc: netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, spacemit@lists.linux.dev, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, Longbin Li Subject: Re: [PATCH net-next v3 3/3] net: stmmac: Add glue layer for Spacemit K3 SoC Message-ID: References: <20260128072931.875041-1-inochiama@gmail.com> <20260128072931.875041-4-inochiama@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Jan 28, 2026 at 05:16:46PM +0800, Vivian Wang wrote: > Hi Inochi, > > I have some comments below. > > On 1/28/26 15:29, Inochi Amaoto wrote: > > The etherenet controller on Spacemit K3 SoC is Synopsys DesignWare > Typo: etherenet -> ethernet > > MAC (version 5.40a), with the following special point: > Nit: point -> points  Thanks > > 1. The rate of the tx clock line is auto changed when the mac speed > > rate is changed, and no need for changing the input tx clock. > > 2. This controller require a extra syscon device to configure the > > interface type, enable wake up interrupt and delay configuration > > if needed. > > > > Add Spacemit dwmac driver support on the Spacemit K3 SoC. > > > > Signed-off-by: Inochi Amaoto > > --- > > drivers/net/ethernet/stmicro/stmmac/Kconfig | 12 + > > drivers/net/ethernet/stmicro/stmmac/Makefile | 1 + > > .../ethernet/stmicro/stmmac/dwmac-spacemit.c | 218 ++++++++++++++++++ > > 3 files changed, 231 insertions(+) > > create mode 100644 drivers/net/ethernet/stmicro/stmmac/dwmac-spacemit.c > > > > [...] > > > > + > > +/* dline register bits */ > > +#define RGMII_RX_DLINE_EN BIT(0) > > +#define RGMII_RX_DLINE_STEP GENMASK(5, 4) > > +#define RGMII_RX_DLINE_CODE GENMASK(15, 8) > > +#define RGMII_TX_DLINE_EN BIT(16) > > +#define RGMII_TX_DLINE_STEP GENMASK(21, 20) > > +#define RGMII_TX_DLINE_CODE GENMASK(31, 24) > > + > > +#define MAX_DLINE_DELAY_CODE 0xff > > +#define MAX_WORKED_DELAY 2800 > > + > > +/* Note: the delay step value is at 0.1ps */ > > +static const unsigned int k3_delay_step_10x[4] = { > > + 367, 493, 559, 685 > > +}; > > + > > +static int spacemit_dwmac_set_delay(struct regmap *apmu, > > + unsigned int dline_offset, > > + unsigned int tx_code, unsigned int tx_config, > > + unsigned int rx_code, unsigned int rx_config) > > +{ > > + unsigned int mask, val; > > + > > + mask = RGMII_TX_DLINE_STEP | RGMII_TX_DLINE_CODE | RGMII_TX_DLINE_EN | > > + RGMII_RX_DLINE_STEP | RGMII_RX_DLINE_CODE | RGMII_RX_DLINE_EN; > > + val = FIELD_PREP(RGMII_TX_DLINE_STEP, tx_config) | > > + FIELD_PREP(RGMII_TX_DLINE_CODE, tx_code) | RGMII_TX_DLINE_EN | > > + FIELD_PREP(RGMII_RX_DLINE_STEP, rx_config) | > > + FIELD_PREP(RGMII_RX_DLINE_CODE, rx_code) | RGMII_RX_DLINE_EN; > > + > > + return regmap_update_bits(apmu, dline_offset, mask, val); > > +} > > + > > +static int spacemit_dwmac_detected_delay_value(unsigned int delay, > > + unsigned int *config) > > +{ > > + unsigned int best_delay = 0; > > + unsigned int best_config = 0; > > + int best_code = 0; > > + int i; > > + > > + if (delay == 0) > > + return 0; > > + > > + if (delay > MAX_WORKED_DELAY) > > + return -EINVAL; > > + > > + /* > > + * Note K3 require a specific factor for calculate > > + * the delay, in this scenario it is 0.9. So the > > + * formula is code * step / 10 * 0.9 > > + */ > > + for (i = 0; i < ARRAY_SIZE(k3_delay_step_10x); i++) { > > + unsigned int step = k3_delay_step_10x[i]; > > + int code = DIV_ROUND_CLOSEST(delay * 10 * 10, step * 9); > > + unsigned int tmp = code * step * 9 / 10 / 10; > > + > > + if (abs(tmp - delay) < abs(best_delay - delay)) { > > + best_code = code; > > + best_delay = tmp; > > + best_config = i; > > + } > > + } > > + > > + *config = best_config; > > + > > + return best_code; > > Is this really necessary? For K1 I just used the smallest step size. > > It seems to me you have, for the smallest step size, about 36.7ps * 0.9 > = 33ps per step. Theoretically speaking that lets you fine tune the > delay to within 1% of the 2ns total required RGMII delay (MAC + PCB + > PHY). In practice this number shouldn't be that marginal.  > I think it is reasonable, I will take you advice and use the smallest step size. Regards, Inochi