Re: [PATCH v1] spi: spi-mtk-nor: Optimize timeout for dma read
From: AngeloGioacchino Del Regno
Date: Fri Nov 11 2022 - 04:16:48 EST
Il 11/11/22 05:16, Bayi Cheng (程八意) ha scritto:
On Fri, 2022-11-04 at 07:53 +0000, Bayi Cheng (程八意) wrote:
On Thu, 2022-11-03 at 22:35 +0000, David Laight wrote:
From: AngeloGioacchino Del Regno
Sent: 03 November 2022 09:44
Il 03/11/22 06:28, Bayi Cheng ha scritto:
From: bayi cheng <bayi.cheng@xxxxxxxxxxxx>
The timeout value of the current dma read is unreasonable. For
example,
If the spi flash clock is 26Mhz, It will takes about 1.3ms to
read a
4KB data in spi mode. But the actual measurement exceeds 50s
when
a
dma read timeout is encountered.
In order to be more accurately, It is necessary to use
msecs_to_jiffies,
After modification, the measured timeout value is about 130ms.
Signed-off-by: bayi cheng <bayi.cheng@xxxxxxxxxxxx>
---
drivers/spi/spi-mtk-nor.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/spi/spi-mtk-nor.c b/drivers/spi/spi-mtk-
nor.c
index d167699a1a96..3d989db80ee9 100644
--- a/drivers/spi/spi-mtk-nor.c
+++ b/drivers/spi/spi-mtk-nor.c
@@ -354,7 +354,7 @@ static int mtk_nor_dma_exec(struct mtk_nor
*sp, u32 from, unsigned int length,
dma_addr_t dma_addr)
{
int ret = 0;
- ulong delay;
+ ulong delay, timeout;
u32 reg;
writel(from, sp->base + MTK_NOR_REG_DMA_FADR);
@@ -376,15 +376,16 @@ static int mtk_nor_dma_exec(struct
mtk_nor
*sp, u32 from, unsigned int length,
mtk_nor_rmw(sp, MTK_NOR_REG_DMA_CTL, MTK_NOR_DMA_START,
0);
delay = CLK_TO_US(sp, (length + 5) * BITS_PER_BYTE);
+ timeout = (delay + 1) * 100;
if (sp->has_irq) {
if (!wait_for_completion_timeout(&sp->op_done,
- (delay + 1) *
100))
+ msecs_to_jiffies(max_t(size_t, timeout /
1000,
10))))
You're giving a `size_t` variable to msecs_to_jiffies(), but
checking `jiffies.h`,
this function takes a `const unsigned int` param.
Please change the type to match that.
The type shouldn't matter at all.
What matters is the domain of the value.
Quite why you need to use max_t(size_t, ...) is another matter.
timeout is ulong so max(timeout/1000, 10ul) should be fine.
But is ulong even right?
The domain of the value is almost certainly the same on 32bit and
64bit.
So you almost certainly need u32 or u64.
David
Hi David & Angelo
Thank you for your comments!
To sum up, I think the next version will make the following two
changes:
1, The timeout value will not exceed u32, so the type of timeout will
be changed from ulong to u32.
2, Change msecs_to_jiffies(max_t(size_t, timeout / 1000, 10)) to be
msecs_to_jiffies(max(timeout / 1000, 10U)).
If you think these changes are not enough, please let me know,
Thanks！
Best Regards,
Bayi
Hi Angelo, Hi David,
Just a gentle ping on this.
Could you please review this patch and give us some suggestion?
PS: With your permission, I will make the following changes in the next
version:
Change in v2:
-Change the type of "timeout" from ulong to u32.
-Replace max_t with max.
I still recommend to use usecs_to_jiffies() when appropriate, instead of
converting usecs to msecs and using msecs_to_jiffies().
As for the rest in your list: yes, please.
Regards,
Angelo
Thanks.
BRs,
Bayi Cheng
Aside from that, your `timeout` variable contains a timeout in
microseconds and
this means that actually using msecs_to_jiffies() is suboptimal
here.
Please use usecs_to_jiffies() instead.
Regards,
Angelo
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