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Mon, 02 Mar 2026 07:14:00 -0800 (PST) From: Iker Pedrosa Date: Mon, 02 Mar 2026 16:13:28 +0100 Subject: [PATCH 07/10] mmc: sdhci-of-k1: add comprehensive SDR tuning support Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260302-orangepi-sd-card-uhs-v1-7-89c219973c0c@gmail.com> References: <20260302-orangepi-sd-card-uhs-v1-0-89c219973c0c@gmail.com> In-Reply-To: <20260302-orangepi-sd-card-uhs-v1-0-89c219973c0c@gmail.com> To: Ulf Hansson , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Yixun Lan , Adrian Hunter , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti Cc: Michael Opdenacker , Javier Martinez Canillas , linux-mmc@vger.kernel.org, devicetree@vger.kernel.org, linux-riscv@lists.infradead.org, spacemit@lists.linux.dev, linux-kernel@vger.kernel.org, Iker Pedrosa X-Mailer: b4 0.14.2 Implement software tuning algorithm to enable UHS-I SDR modes for SD card operation. This adds both TX and RX delay line tuning based on the SpacemiT K1 controller capabilities. Key features: - Conditional tuning: only tune when SD card is present and for high-speed modes (=E2=89=A5100MHz) - TX tuning: configure transmit delay line with default values (dline_reg=3D0, delaycode=3D127) to ensure optimal signal output timing - RX tuning: test full delay range (0-255) with window detection algorithm to find optimal receive timing - Retry mechanism: multiple fallback delays within optimal window for improved reliability - Complete register support: add delay line control and configuration register definitions for fine-grained timing control Signed-off-by: Iker Pedrosa --- drivers/mmc/host/sdhci-of-k1.c | 118 +++++++++++++++++++++++++++++++++++++= ++++ 1 file changed, 118 insertions(+) diff --git a/drivers/mmc/host/sdhci-of-k1.c b/drivers/mmc/host/sdhci-of-k1.c index 34a1b9c359193be7dd5f07d1f3d6565b5f40e7ff..95b016bfb5598acea4166257d12= af54d945a0c13 100644 --- a/drivers/mmc/host/sdhci-of-k1.c +++ b/drivers/mmc/host/sdhci-of-k1.c @@ -88,6 +88,12 @@ #define SDHC_TX_DLINE_REG_MASK GENMASK(23, 16) =20 #define SPACEMIT_RX_DLINE_REG 9 +#define SPACEMIT_RX_TUNE_DELAY_MIN 0x0 +#define SPACEMIT_RX_TUNE_DELAY_MAX 0xFF +#define SPACEMIT_RX_TUNE_DELAY_STEP 0x1 + +#define SPACEMIT_TX_TUNING_DLINE_REG 0x00 +#define SPACEMIT_TX_TUNING_DELAYCODE 127 =20 struct spacemit_sdhci_host { struct clk *clk_core; @@ -256,6 +262,118 @@ static unsigned int spacemit_sdhci_clk_get_max_clock(= struct sdhci_host *host) return clk_get_rate(pltfm_host->clk); } =20 +static int spacemit_sdhci_execute_tuning(struct sdhci_host *host, u32 opco= de) +{ + int ret =3D 0; + int i; + bool pass_window[SPACEMIT_RX_TUNE_DELAY_MAX + 1] =3D {false}; + int pass_len =3D 0, pass_start =3D 0, max_pass_len =3D 0, max_pass_start = =3D 0; + u8 final_delay; + struct mmc_host *mmc =3D host->mmc; + struct mmc_ios ios =3D mmc->ios; + + /* + * Tuning is required for SDR50/SDR104, HS200/HS400 cards and + * if clock frequency is greater than 100MHz in these modes. + */ + if (host->clock < 100 * 1000 * 1000 || + !(ios.timing =3D=3D MMC_TIMING_MMC_HS200 || + ios.timing =3D=3D MMC_TIMING_UHS_SDR50 || + ios.timing =3D=3D MMC_TIMING_UHS_SDR104)) + return 0; + + if (!(mmc->caps2 & MMC_CAP2_NO_SD) && !mmc->ops->get_cd(mmc)) + return 0; + + if (mmc->caps2 & MMC_CAP2_NO_MMC) { + spacemit_sdhci_set_tx_dline_reg(host, SPACEMIT_TX_TUNING_DLINE_REG); + spacemit_sdhci_set_tx_delay(host, SPACEMIT_TX_TUNING_DELAYCODE); + spacemit_sdhci_tx_tuning_prepare(host); + + dev_dbg(mmc_dev(host->mmc), "TX tuning: dline_reg=3D%d, delaycode=3D%d\n= ", + SPACEMIT_TX_TUNING_DLINE_REG, SPACEMIT_TX_TUNING_DELAYCODE); + } + + spacemit_sdhci_prepare_tuning(host); + + for (i =3D SPACEMIT_RX_TUNE_DELAY_MIN; i <=3D SPACEMIT_RX_TUNE_DELAY_MAX; + i +=3D SPACEMIT_RX_TUNE_DELAY_STEP) { + spacemit_sdhci_set_rx_delay(host, i); + + ret =3D mmc_send_tuning(host->mmc, opcode, NULL); + pass_window[i] =3D (ret =3D=3D 0); + + dev_dbg(mmc_dev(host->mmc), "RX delay %d: %s\n", + i, pass_window[i] ? "pass" : "fail"); + } + + for (i =3D SPACEMIT_RX_TUNE_DELAY_MIN; i <=3D SPACEMIT_RX_TUNE_DELAY_MAX; + i +=3D SPACEMIT_RX_TUNE_DELAY_STEP) { + if (pass_window[i]) { + if (pass_len =3D=3D 0) + pass_start =3D i; + pass_len++; + } else { + if (pass_len > max_pass_len) { + max_pass_len =3D pass_len; + max_pass_start =3D pass_start; + } + pass_len =3D 0; + } + } + + if (pass_len > max_pass_len) { + max_pass_len =3D pass_len; + max_pass_start =3D pass_start; + } + + if (max_pass_len < 3) { + dev_err(mmc_dev(host->mmc), "Tuning failed: no stable window found\n"); + return -EIO; + } + + final_delay =3D max_pass_start + max_pass_len / 2; + spacemit_sdhci_set_rx_delay(host, final_delay); + ret =3D mmc_send_tuning(host->mmc, opcode, NULL); + if (ret) { + u8 retry_delays[] =3D { + max_pass_start + max_pass_len / 4, + max_pass_start + (3 * max_pass_len) / 4, + max_pass_start, + max_pass_start + max_pass_len - 1 + }; + int retry_count =3D ARRAY_SIZE(retry_delays); + + dev_warn(mmc_dev(mmc), "Primary delay %d failed, trying alternatives\n", + final_delay); + + for (i =3D 0; i < retry_count; i++) { + if (retry_delays[i] >=3D SPACEMIT_RX_TUNE_DELAY_MIN && + retry_delays[i] <=3D SPACEMIT_RX_TUNE_DELAY_MAX) { + spacemit_sdhci_set_rx_delay(host, retry_delays[i]); + ret =3D mmc_send_tuning(host->mmc, opcode, NULL); + if (!ret) { + final_delay =3D retry_delays[i]; + dev_info(mmc_dev(mmc), "Retry successful with delay %d\n", + final_delay); + break; + } + } + } + + if (ret) { + dev_err(mmc_dev(mmc), "All retry attempts failed\n"); + return -EIO; + } + } + + dev_dbg(mmc_dev(host->mmc), + "Tuning successful: window %d-%d, using delay %d\n", + max_pass_start, max_pass_start + max_pass_len - 1, final_delay); + + return 0; +} + static int spacemit_sdhci_pre_select_hs400(struct mmc_host *mmc) { struct sdhci_host *host =3D mmc_priv(mmc); --=20 2.53.0