From: Aswath Govindraju a-govindraju@ti.com
[ Upstream commit 7b1d96813317358312440d0d07abbfbeb0ef8d22 ]
This reverts commit 13d515c796 (spi: omap2-mcspi: Switch to readl_poll_timeout()).
The amount of time spent polling for the MCSPI_CHSTAT bits to be set on AM335x-icev2 platform is less than 1us (about 0.6us) in most cases, with or without using DMA. So, in most cases the function need not sleep. Also, setting the sleep_usecs to zero would not be optimal here because ktime_add_us() used in readl_poll_timeout() is slower compared to the direct addition used after the revert. So, it is sub-optimal to use readl_poll_timeout in this case.
When DMA is not enabled, this revert results in an increase of about 27% in throughput and decrease of about 20% in CPU usage. However, the CPU usage and throughput are almost the same when used with DMA.
Therefore, fix this by reverting the commit which switched to using readl_poll_timeout().
Fixes: 13d515c796ad ("spi: omap2-mcspi: Switch to readl_poll_timeout()") Signed-off-by: Aswath Govindraju a-govindraju@ti.com Link: https://lore.kernel.org/r/20200910122624.8769-1-a-govindraju@ti.com Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/spi/spi-omap2-mcspi.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c index 1c9478e6e5d99..d4c9510af3931 100644 --- a/drivers/spi/spi-omap2-mcspi.c +++ b/drivers/spi/spi-omap2-mcspi.c @@ -24,7 +24,6 @@ #include <linux/of.h> #include <linux/of_device.h> #include <linux/gcd.h> -#include <linux/iopoll.h>
#include <linux/spi/spi.h>
@@ -348,9 +347,19 @@ static void omap2_mcspi_set_fifo(const struct spi_device *spi,
static int mcspi_wait_for_reg_bit(void __iomem *reg, unsigned long bit) { - u32 val; - - return readl_poll_timeout(reg, val, val & bit, 1, MSEC_PER_SEC); + unsigned long timeout; + + timeout = jiffies + msecs_to_jiffies(1000); + while (!(readl_relaxed(reg) & bit)) { + if (time_after(jiffies, timeout)) { + if (!(readl_relaxed(reg) & bit)) + return -ETIMEDOUT; + else + return 0; + } + cpu_relax(); + } + return 0; }
static int mcspi_wait_for_completion(struct omap2_mcspi *mcspi,