Hi,
On Thu, 3 Mar 2011 09:07:22 +0800
"Jayaraman, Venkat" <[email protected]> wrote:
> Feng,
> The attached patch causes a panic. There is some bad pointer
> reference somewhere in the changed code. Also increasing the time to
> 10s still produces the message.
I guess it's a 10ms not 10s here?
And sorry for the panic, I didn't try the patch on my platform as the
error msg doesn't show up (I did see the msg before by myself).
Here is a updated one, which consider the driver init phase where
there is no valid spi_transfer yet.
--------------------
diff --git a/drivers/spi/dw_spi.c b/drivers/spi/dw_spi.c
index 0f7ed08..0262992 100644
--- a/drivers/spi/dw_spi.c
+++ b/drivers/spi/dw_spi.c
@@ -164,7 +164,16 @@ static inline void mrst_spi_debugfs_remove(struct dw_spi
*dws)
static void wait_till_not_busy(struct dw_spi *dws)
{
- unsigned long end = jiffies + 1 + usecs_to_jiffies(5000);
+ int end, wait_us;
+
+ if (dws->cur_chip) {
+ wait_us = dws->fifo_len * 16 * USEC_PER_SEC /
dws->cur_chip->speed_hz;
+ /* Give it a 50% safe buffer */
+ wait_us += wait_us >> 1;
+ } else
+ wait_us = 5000;
+
+ end = jiffies + 1 + usecs_to_jiffies(wait_us);
while (time_before(jiffies, end)) {
if (!(dw_readw(dws, sr) & SR_BUSY))
@@ -172,7 +181,8 @@ static void wait_till_not_busy(struct dw_spi *dws)
cpu_relax();
}
dev_err(&dws->master->dev,
- "DW SPI: Status keeps busy for 5000us after a read/write!\n");
+ "DW SPI: HW keeps busy for %d us after a read/write!\n",
+ wait_us);
}
static void flush(struct dw_spi *dws)
Thanks,
Feng
>
> Thanks
> Venkat
>
> -----Original Message-----
> From: Tang, Feng
> Sent: Tuesday, March 01, 2011 7:41 PM
> To: Tang, Feng
> Cc: Jayaraman, Venkat; [email protected]; [email protected]
> Subject: Re: [Meego-kernel] Question on Designware SPI Controller
> Driver
>
> On Wed, 2 Mar 2011 10:41:18 +0800
> "Tang, Feng" <[email protected]> wrote:
>
> > Hi Venkat,
> >
> > If you disable the "mrst" earlyprintk, then there is no conflict.
> >
> > As I said in last email, if you still randomly see it, it's fine.
> > The basic idea for the busy wait (code is listed here) is simple,
> > after write/read the FIFO wait till the HW register tell us it's
> > not busy
> >
> > static void wait_till_not_busy(struct dw_spi *dws) {
> > unsigned long end = jiffies + 1 + usecs_to_jiffies(5000);
> >
> > while (time_before(jiffies, end)) {
> > if (!(dw_readw(dws, sr) & SR_BUSY))
> > return;
> > cpu_relax();
> > }
> > dev_err(&dws->master->dev,
> > "DW SPI: Status keeps busy for 5000us after a
> > read/write!\n"); }
> >
> > 5000 us should be enough for dumping the DW spi controller's FIFO
> > (which is 40 words deep) even for a low speed UART slave device at
> > 115200 bps.
> >
> > If you still see lots of that message, can you enlarge that 5000 to
> > 100000 to check if it's gone?
> >
> > Thanks,
> > Feng
>
>
> Venkat,
>
> You can also try the attached debug patch, which adjust the wait time
> dynamically.
>
> ----------------------------------------------------------
> diff --git a/drivers/spi/dw_spi.c b/drivers/spi/dw_spi.c index
> 0f7ed08..e136897 100644 --- a/drivers/spi/dw_spi.c
> +++ b/drivers/spi/dw_spi.c
> @@ -164,7 +164,13 @@ static inline void
> mrst_spi_debugfs_remove(struct dw_spi *dws)
> static void wait_till_not_busy(struct dw_spi *dws) {
> - unsigned long end = jiffies + 1 + usecs_to_jiffies(5000);
> + int end, wait_us;
> +
> + wait_us = dws->fifo_len * 16 * USEC_PER_SEC /
> dws->cur_chip->speed_hz;
> + /* Give it a 50% safe buffer */
> + wait_us += wait_us >> 1;
> +
> + end = jiffies + 1 + usecs_to_jiffies(wait_us);
>
> while (time_before(jiffies, end)) {
> if (!(dw_readw(dws, sr) & SR_BUSY))
> @@ -172,7 +178,8 @@ static void wait_till_not_busy(struct dw_spi *dws)
> cpu_relax();
> }
> dev_err(&dws->master->dev,
> - "DW SPI: Status keeps busy for 5000us after a
> read/write!\n");
> + "DW SPI: HW keeps busy for %d us after a
> read/write!\n",
> + wait_us);
> }
>
> static void flush(struct dw_spi *dws)
>
>
> Thanks,
> Feng
>
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