mmc: tmio: avoid glitches when resetting

If we reset because of an error, we need to preserve values for the
clock frequency. Otherwise, glitches may be seen on the bus.

To achieve that, we introduce a 'preserve' parameter to the reset
function and the IP core specific reset callbacks to handle everything
accordingly.

Reported-by: Yoshihiro Shimoda <[e-mail]>
Signed-off-by: Wolfram Sang <[e-mail]>
Tested-by: Yoshihiro Shimoda <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/mmc/host/renesas_sdhi_core.c

···
 #define HOST_MODE_GEN3_32BIT	(HOST_MODE_GEN3_WMODE | HOST_MODE_GEN3_BUSWIDTH)
 #define HOST_MODE_GEN3_64BIT	0
 
-#define CTL_SDIF_MODE	0xe6
-#define SDIF_MODE_HS400		BIT(0)
-
 #define SDHI_VER_GEN2_SDR50	0x490c
 #define SDHI_VER_RZ_A1		0x820b
 /* very old datasheets said 0x490c for SDR104, too. They are wrong! */
···
 }
 
 /* only populated for TMIO_MMC_MIN_RCAR2 */
-static void renesas_sdhi_reset(struct tmio_mmc_host *host)
+static void renesas_sdhi_reset(struct tmio_mmc_host *host, bool preserve)
 {
 	struct renesas_sdhi *priv = host_to_priv(host);
 	int ret;
 	u16 val;
 
-	if (priv->rstc) {
-		reset_control_reset(priv->rstc);
-		/* Unknown why but without polling reset status, it will hang */
-		read_poll_timeout(reset_control_status, ret, ret == 0, 1, 100,
-				  false, priv->rstc);
-		/* At least SDHI_VER_GEN2_SDR50 needs manual release of reset */
-		sd_ctrl_write16(host, CTL_RESET_SD, 0x0001);
-		priv->needs_adjust_hs400 = false;
-		renesas_sdhi_set_clock(host, host->clk_cache);
-	} else if (priv->scc_ctl) {
-		renesas_sdhi_scc_reset(host, priv);
+	if (!preserve) {
+		if (priv->rstc) {
+			reset_control_reset(priv->rstc);
+			/* Unknown why but without polling reset status, it will hang */
+			read_poll_timeout(reset_control_status, ret, ret == 0, 1, 100,
+					  false, priv->rstc);
+			/* At least SDHI_VER_GEN2_SDR50 needs manual release of reset */
+			sd_ctrl_write16(host, CTL_RESET_SD, 0x0001);
+			priv->needs_adjust_hs400 = false;
+			renesas_sdhi_set_clock(host, host->clk_cache);
+		} else if (priv->scc_ctl) {
+			renesas_sdhi_scc_reset(host, priv);
+		}
 	}
 
 	if (sd_ctrl_read16(host, CTL_VERSION) >= SDHI_VER_GEN3_SD) {

drivers/mmc/host/tmio_mmc.c

···
 	tmio_mmc_clk_start(host);
 }
 
-static void tmio_mmc_reset(struct tmio_mmc_host *host)
+static void tmio_mmc_reset(struct tmio_mmc_host *host, bool preserve)
 {
 	sd_ctrl_write16(host, CTL_RESET_SDIO, 0x0000);
 	usleep_range(10000, 11000);

drivers/mmc/host/tmio_mmc.h

···
 #define CTL_DMA_ENABLE 0xd8
 #define CTL_RESET_SD 0xe0
 #define CTL_VERSION 0xe2
+#define CTL_SDIF_MODE 0xe6 /* only known on R-Car 2+ */
 
 /* Definitions for values the CTL_STOP_INTERNAL_ACTION register can take */
 #define TMIO_STOP_STP		BIT(0)
···
 
 /* Definitions for values the CTL_DMA_ENABLE register can take */
 #define DMA_ENABLE_DMASDRW	BIT(1)
+
+/* Definitions for values the CTL_SDIF_MODE register can take */
+#define SDIF_MODE_HS400		BIT(0) /* only known on R-Car 2+ */
 
 /* Define some IRQ masks */
 /* This is the mask used at reset by the chip */
···
 	int (*multi_io_quirk)(struct mmc_card *card,
 			      unsigned int direction, int blk_size);
 	int (*write16_hook)(struct tmio_mmc_host *host, int addr);
-	void (*reset)(struct tmio_mmc_host *host);
+	void (*reset)(struct tmio_mmc_host *host, bool preserve);
 	bool (*check_retune)(struct tmio_mmc_host *host, struct mmc_request *mrq);
 	void (*fixup_request)(struct tmio_mmc_host *host, struct mmc_request *mrq);
 	unsigned int (*get_timeout_cycles)(struct tmio_mmc_host *host);

drivers/mmc/host/tmio_mmc_core.c

···
 	sd_ctrl_write16(host, CTL_SD_MEM_CARD_OPT, reg);
 }
 
-static void tmio_mmc_reset(struct tmio_mmc_host *host)
+static void tmio_mmc_reset(struct tmio_mmc_host *host, bool preserve)
 {
+	u16 card_opt, clk_ctrl, sdif_mode;
+
+	if (preserve) {
+		card_opt = sd_ctrl_read16(host, CTL_SD_MEM_CARD_OPT);
+		clk_ctrl = sd_ctrl_read16(host, CTL_SD_CARD_CLK_CTL);
+		if (host->pdata->flags & TMIO_MMC_MIN_RCAR2)
+			sdif_mode = sd_ctrl_read16(host, CTL_SDIF_MODE);
+	}
+
 	/* FIXME - should we set stop clock reg here */
 	sd_ctrl_write16(host, CTL_RESET_SD, 0x0000);
 	usleep_range(10000, 11000);
···
 	tmio_mmc_abort_dma(host);
 
 	if (host->reset)
-		host->reset(host);
+		host->reset(host, preserve);
 
 	sd_ctrl_write32_as_16_and_16(host, CTL_IRQ_MASK, host->sdcard_irq_mask_all);
 	host->sdcard_irq_mask = host->sdcard_irq_mask_all;
···
 	if (host->pdata->flags & TMIO_MMC_SDIO_IRQ) {
 		sd_ctrl_write16(host, CTL_SDIO_IRQ_MASK, host->sdio_irq_mask);
 		sd_ctrl_write16(host, CTL_TRANSACTION_CTL, 0x0001);
+	}
+
+	if (preserve) {
+		sd_ctrl_write16(host, CTL_SD_MEM_CARD_OPT, card_opt);
+		sd_ctrl_write16(host, CTL_SD_CARD_CLK_CTL, clk_ctrl);
+		if (host->pdata->flags & TMIO_MMC_MIN_RCAR2)
+			sd_ctrl_write16(host, CTL_SDIF_MODE, sdif_mode);
 	}
 
 	if (host->mmc->card)
···
 
 	spin_unlock_irqrestore(&host->lock, flags);
 
-	tmio_mmc_reset(host);
+	tmio_mmc_reset(host, true);
 
 	/* Ready for new calls */
 	host->mrq = NULL;
···
 		tmio_mmc_power_off(host);
 		/* For R-Car Gen2+, we need to reset SDHI specific SCC */
 		if (host->pdata->flags & TMIO_MMC_MIN_RCAR2)
-			tmio_mmc_reset(host);
+			tmio_mmc_reset(host, false);
 
 		host->set_clock(host, 0);
 		break;
···
 		_host->sdcard_irq_mask_all = TMIO_MASK_ALL;
 
 	_host->set_clock(_host, 0);
-	tmio_mmc_reset(_host);
+	tmio_mmc_reset(_host, false);
 
 	spin_lock_init(&_host->lock);
 	mutex_init(&_host->ios_lock);
···
 	struct tmio_mmc_host *host = dev_get_drvdata(dev);
 
 	tmio_mmc_clk_enable(host);
-	tmio_mmc_reset(host);
+	tmio_mmc_reset(host, false);
 
 	if (host->clk_cache)
 		host->set_clock(host, host->clk_cache);