rockchip: spi: add driver-data and a 'rxonly_manages_fifo' flag

The SPI controller's documentation (I only had access to the RK3399,
RK3368 and PX30 TRMs) specifies that, when operating in master-mode,
the controller will stop the SCLK to avoid RXFIFO overruns and TXFIFO
underruns.  Looks like my worries that we'd need to support DMA-330
(aka PL330) to make any further progress were unfounded.

This adds a driver-data structure to capture hardware-specific
settings of individual controller instances (after all, we don't know
if all versions are well-behaved) and adds a 'master_manages_fifo'
flag to it.  The first use of said flag is in the optimised
receive-only transfer-handler, which can now request 64Kframe
(i.e. 128KByte) bursts of data on each reprogramming of CTRLR1
(i.e. every time through the loop).

This improves throughput to 46.85MBit/s (a 94.65% bus-utilisation).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

diff --git a/drivers/spi/rk_spi.c b/drivers/spi/rk_spi.c
index fec41a42439fd78defd6c51a8fcefaac7f1bbcb1..7b39d1c9e7906bcf111c5e81c637b8715dfc2965 100644 (file)
--- a/drivers/spi/rk_spi.c
+++ b/drivers/spi/rk_spi.c
@@ -26,6 +26,11 @@
 /* Change to 1 to output registers at the start of each transaction */
 #define DEBUG_RK_SPI   0
 
+struct rockchip_spi_params {
+       /* RXFIFO overruns and TXFIFO underruns stop the master clock */
+       bool master_manages_fifo;
+};
+
 struct rockchip_spi_platdata {
 #if CONFIG_IS_ENABLED(OF_PLATDATA)
        struct dtd_rockchip_rk3288_spi of_plat;
@@ -364,6 +369,15 @@ static inline int rockchip_spi_16bit_reader(struct udevice *dev,
                return 0;
        }
 
+       /*
+        * If we know that the hardware will manage RXFIFO overruns
+        * (i.e. stop the SPI clock until there's space in the FIFO),
+        * we the allow largest possible chunk size that can be
+        * represented in CTRLR1.
+        */
+       if (data && data->master_manages_fifo)
+               max_chunk_size = 0x10000;
+
        // rockchip_spi_configure(dev, mode, size)
        rkspi_enable_chip(regs, false);
        clrsetbits_le32(&regs->ctrlr0,
@@ -524,10 +538,16 @@ static const struct dm_spi_ops rockchip_spi_ops = {
         */
 };
 
+const  struct rockchip_spi_params rk3399_spi_params = {
+       .master_manages_fifo = true,
+};
+
 static const struct udevice_id rockchip_spi_ids[] = {
        { .compatible = "rockchip,rk3288-spi" },
-       { .compatible = "rockchip,rk3368-spi" },
-       { .compatible = "rockchip,rk3399-spi" },
+       { .compatible = "rockchip,rk3368-spi",
+         .data = (ulong)&rk3399_spi_params },
+       { .compatible = "rockchip,rk3399-spi",
+         .data = (ulong)&rk3399_spi_params },
        { }
 };