at32ap700x spi: enable pullups on MISO

This is a minor tweak to the at32ap700x pin configuration for the SPI
input pin (MISO), enabling the on-chip weak pullup (typical 190K) to

  (a) ensure a fixed data value for missing or input-only slaves;

  (b) prevent power waste associated with inputs floating near VDDIO/2.

Atmel's boards have no external pullup or pulldown on these pins, so
it's unlikely other boards would address these issues with external
pulldowns.  Were there trouble, board-specific code could turn off
the relevant pullup(s).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>

diff --git a/arch/avr32/mach-at32ap/at32ap700x.c b/arch/avr32/mach-at32ap/at32ap700x.c
index a9ae7bb..a2e7b96 100644 (file)
--- a/arch/avr32/mach-at32ap/at32ap700x.c
+++ b/arch/avr32/mach-at32ap/at32ap700x.c
@@ -1181,7 +1181,8 @@ at32_add_device_spi(unsigned int id, struct spi_board_info *b, unsigned int n)
        switch (id) {
        case 0:
                pdev = &atmel_spi0_device;
-               select_peripheral(PA(0),  PERIPH_A, 0); /* MISO  */
+               /* pullup MISO so a level is always defined */
+               select_peripheral(PA(0),  PERIPH_A, AT32_GPIOF_PULLUP);
                select_peripheral(PA(1),  PERIPH_A, 0); /* MOSI  */
                select_peripheral(PA(2),  PERIPH_A, 0); /* SCK   */
                at32_spi_setup_slaves(0, b, n, spi0_pins);
@@ -1189,7 +1190,8 @@ at32_add_device_spi(unsigned int id, struct spi_board_info *b, unsigned int n)
 
        case 1:
                pdev = &atmel_spi1_device;
-               select_peripheral(PB(0),  PERIPH_B, 0); /* MISO  */
+               /* pullup MISO so a level is always defined */
+               select_peripheral(PB(0),  PERIPH_B, AT32_GPIOF_PULLUP);
                select_peripheral(PB(1),  PERIPH_B, 0); /* MOSI  */
                select_peripheral(PB(5),  PERIPH_B, 0); /* SCK   */
                at32_spi_setup_slaves(1, b, n, spi1_pins);