mmc: andes: ftsdc010: Only MMC block commands use DMA mode for data transfer (torvalds#223)

Determine if DMA mode should be used for the current command.
DMA mode is preferred for block transfers to optimize performance,
but it may not be used in certain situations:
1. Only block transfer commands (CMD17, CMD18, CMD24, CMD25)
   will utilize DMA to minimize overhead for smaller commands.
2. PIO mode is used for CMD6 to avoid potential hangup issues
   during system resumes on specific FPGA implementations.

Signed-off-by: CL Wang <[email protected]>
Reviewed-on: https://gitea.andestech.com/RD-SW/linux/pulls/223
Reviewed-by: randolph <[email protected]>
Reviewed-by: Leo Yu-Chi Liang <[email protected]>
Reviewed-by: Locus Wei-Han Chen <[email protected]>
Reviewed-by: Tim Shih-Ting OuYang <[email protected]>
Co-authored-by: CL Wang <[email protected]>
Co-committed-by: CL Wang <[email protected]>

Author: CL Wang

drivers/mmc/host/ftsdc010.c

@@ -162,9 +162,32 @@ static void dbg_dumpregs(struct ftsdc_host *host, char *prefix)
 
 #endif /* CONFIG_MMC_DEBUG */
 
-static inline bool ftsdc_dmaexist(struct ftsdc_host *host)
+/**
+ * ftsdc_use_dma_by_cmd - Check if the current command can use DMA mode
+ * @host: The FTSDC host containing the current command and DMA channel status
+ *
+ * Returns true if the command can use DMA mode, false otherwise.
+ */
+static bool ftsdc_use_dma_by_cmd(struct ftsdc_host *host)
 {
-	return (host->dma.chan != NULL);
+	struct mmc_command *cmd = host->cmd_is_stop ? host->mrq->stop : host->mrq->cmd;
+
+	/*
+	 * Determine if DMA mode should be used for the current command.
+	 * DMA mode is preferred for block transfers to optimize performance,
+	 * but it may not be used in certain situations:
+	 * 1. Only block transfer commands (CMD17, CMD18, CMD24, CMD25)
+	 *    will utilize DMA to minimize overhead for smaller commands.
+	 * 2. PIO mode is used for CMD6 to avoid potential hangup issues
+	 *    during system resume on specific FPGA implementations.
+	 */
+	if (unlikely(!host->dma.chan))
+		return false;
+
+	return (cmd->opcode == MMC_READ_SINGLE_BLOCK ||
+		cmd->opcode == MMC_READ_MULTIPLE_BLOCK ||
+		cmd->opcode == MMC_WRITE_BLOCK ||
+		cmd->opcode == MMC_WRITE_MULTIPLE_BLOCK);
 }
 
 static inline u32 enable_imask(struct ftsdc_host *host, u32 imask)
@@ -724,13 +747,14 @@ static int ftsdc_setup_data(struct ftsdc_host *host, struct mmc_data *data)
 
 	/* enable data transfer which will be pended until cmd is send */
 	dcon |= SDC_DATA_CTRL_REG_DATA_EN;
-	if (ftsdc_dmaexist(host) &&
+	if (ftsdc_use_dma_by_cmd(host) &&
 			((data->blksz * data->blocks) & 0xf) == 0) {
 		newmask &= ~SDC_INT_MASK_REG_FIFO_OVERRUN;
 		dcon |= SDC_DATA_CTRL_REG_DMA_EN;
 		dcon |= SDC_DMA_TYPE_4;
 		host->dodma = true;
-
+	} else {
+		host->dodma = false;
 	}
 	REG_WRITE(dcon, SDC_DATA_CTRL_REG);
 	/* add to IMASK register */
@@ -1175,7 +1199,7 @@ static int ftsdc_state_show(struct seq_file *seq, void *v)
 	seq_printf(seq, "IRQ = %d\n", host->irq);
 	seq_printf(seq, "IRQ enabled = %d\n", host->irq_enabled);
 	seq_printf(seq, "complete what = %d\n", host->complete_what);
-	seq_printf(seq, "dma support = %d\n", ftsdc_dmaexist(host));
+	seq_printf(seq, "dma support = %d\n", host->dma.chan != NULL);
 	seq_printf(seq, "use dma = %d\n", host->dodma);
 
 	return 0;