mmc: atmel-mci: add support for odd clock dividers

Add an odd clock divider capability available from v5xx. It also involves
changing the clock divider calculation, and changing the switch-case
statement to use top-down fallthrough.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

2 files changed, 30 insertions, 19 deletions

diff --git a/drivers/mmc/host/atmel-mci-regs.h b/drivers/mmc/host/atmel-mci-regs.h
index 000b3ad0f5ca..787aba1682bb 100644
--- a/drivers/mmc/host/atmel-mci-regs.h
+++ b/drivers/mmc/host/atmel-mci-regs.h
@@ -31,6 +31,7 @@
 # define ATMCI_MR_PDCFBYTE              (  1 << 13)     /* Force Byte Transfer */
 # define ATMCI_MR_PDCPADV               (  1 << 14)     /* Padding Value */
 # define ATMCI_MR_PDCMODE               (  1 << 15)     /* PDC-oriented Mode */
+# define ATMCI_MR_CLKODD(x)             ((x) << 16)     /* LSB of Clock Divider */
 #define ATMCI_DTOR                      0x0008  /* Data Timeout */
 # define ATMCI_DTOCYC(x)                ((x) <<  0)     /* Data Timeout Cycles */
 # define ATMCI_DTOMUL(x)                ((x) <<  4)     /* Data Timeout Multiplier */
diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
index c56edc4a8e26..e94476beca18 100644
--- a/drivers/mmc/host/atmel-mci.c
+++ b/drivers/mmc/host/atmel-mci.c
@@ -77,6 +77,7 @@ struct atmel_mci_caps {
         bool    has_cstor_reg;
         bool    has_highspeed;
         bool    has_rwproof;
+        bool    has_odd_clk_div;
 };
 
 struct atmel_mci_dma {
@@ -1134,16 +1135,27 @@ static void atmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
                 }
 
                 /* Calculate clock divider */
-                clkdiv = DIV_ROUND_UP(host->bus_hz, 2 * clock_min) - 1;
-                if (clkdiv > 255) {
-                        dev_warn(&mmc->class_dev,
-                                "clock %u too slow; using %lu\n",
-                                clock_min, host->bus_hz / (2 * 256));
-                        clkdiv = 255;
+                if (host->caps.has_odd_clk_div) {
+                        clkdiv = DIV_ROUND_UP(host->bus_hz, clock_min) - 2;
+                        if (clkdiv > 511) {
+                                dev_warn(&mmc->class_dev,
+                                         "clock %u too slow; using %lu\n",
+                                         clock_min, host->bus_hz / (511 + 2));
+                                clkdiv = 511;
+                        }
+                        host->mode_reg = ATMCI_MR_CLKDIV(clkdiv >> 1)
+                                         | ATMCI_MR_CLKODD(clkdiv & 1);
+                } else {
+                        clkdiv = DIV_ROUND_UP(host->bus_hz, 2 * clock_min) - 1;
+                        if (clkdiv > 255) {
+                                dev_warn(&mmc->class_dev,
+                                         "clock %u too slow; using %lu\n",
+                                         clock_min, host->bus_hz / (2 * 256));
+                                clkdiv = 255;
+                        }
+                        host->mode_reg = ATMCI_MR_CLKDIV(clkdiv);
                 }
 
-                host->mode_reg = ATMCI_MR_CLKDIV(clkdiv);
-
                 /*
                  * WRPROOF and RDPROOF prevent overruns/underruns by
                  * stopping the clock when the FIFO is full/empty.
@@ -2014,37 +2026,35 @@ static void __init atmci_get_cap(struct atmel_mci *host)
                         "version: 0x%x\n", version);
 
         host->caps.has_dma = 0;
-        host->caps.has_pdc = 0;
+        host->caps.has_pdc = 1;
         host->caps.has_cfg_reg = 0;
         host->caps.has_cstor_reg = 0;
         host->caps.has_highspeed = 0;
         host->caps.has_rwproof = 0;
+        host->caps.has_odd_clk_div = 0;
 
         /* keep only major version number */
         switch (version & 0xf00) {
-        case 0x100:
-                host->caps.has_pdc = 1;
-                break;
-        case 0x200:
-                host->caps.has_pdc = 1;
-                host->caps.has_rwproof = 1;
-                break;
-        case 0x300:
-        case 0x400:
         case 0x500:
+                host->caps.has_odd_clk_div = 1;
+        case 0x400:
+        case 0x300:
 #ifdef CONFIG_AT_HDMAC
                 host->caps.has_dma = 1;
 #else
-                host->caps.has_dma = 0;
                 dev_info(&host->pdev->dev,
                         "has dma capability but dma engine is not selected, then use pio\n");
 #endif
+                host->caps.has_pdc = 0;
                 host->caps.has_cfg_reg = 1;
                 host->caps.has_cstor_reg = 1;
                 host->caps.has_highspeed = 1;
+        case 0x200:
                 host->caps.has_rwproof = 1;
+        case 0x100:
                 break;
         default:
+                host->caps.has_pdc = 0;
                 dev_warn(&host->pdev->dev,
                                 "Unmanaged mci version, set minimum capabilities\n");
                 break;