mxc_spi: Round up clock divider

PATCH New Benoît Thébaudeau 2 participants 4 messages Aug 10, 2012 – Aug 20, 2012 1 message not in the archive

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Arm i.MX and Layerscape SPI

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Benoît Thébaudeau

author

2012-08-10 18:51 UTC #1 lore raw

PATCH 1/1 mxc_spi: Round up clock divider

Since the input frequency of the API is a maximum that should not be exceeded in order for the devices to operate properly, the SPI clock divider should be rounded up, not truncated.

Signed-off-by Beno?t Th?baudeau <[email protected]>

Cc Wolfgang Denk <[email protected]>

Cc Stefano Babic <[email protected]>

---
 .../drivers/spi/mxc_spi.c                          |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

drivers/spi/mxc_spi.c +2 -2

index 2e15318..cf1462f 100644
@@ -96,7 +96,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 
 	clk_src = mxc_get_clock(MXC_CSPI_CLK);
 
-	div = clk_src / max_hz;
+	div = DIV_ROUND_UP(clk_src, max_hz);
 	div = get_cspi_div(div);
 
 	debug("clk %d Hz, div %d, real clk %d Hz\n",

@@ -147,7 +147,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 	 * The following computation is taken directly from Freescale's code.
 	 */
 	if (clk_src > max_hz) {
-		pre_div = clk_src / max_hz;
+		pre_div = DIV_ROUND_UP(clk_src, max_hz);
 		if (pre_div > 16) {
 			post_div = pre_div / 16;
 			pre_div = 15;

Stefano Babic

2012-08-11 10:37 UTC #2 lore raw

PATCH 1/1 mxc_spi: Round up clock divider

Quoted 4 lines · Beno?t Th?baudeau

Since the input frequency of the API is a maximum that should not be exceeded in order for the devices to operate properly, the SPI clock divider should be rounded up, not truncated.

Hi Beno?t,

Quoted 22 lines

Signed-off-by Beno?t Th?baudeau <[email protected]>

Cc Wolfgang Denk <[email protected]>

Cc Stefano Babic <[email protected]>

---
 .../drivers/spi/mxc_spi.c                          |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

drivers/spi/mxc_spi.c +1 -1

index 2e15318..cf1462f 100644
@@ -96,7 +96,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 
 	clk_src = mxc_get_clock(MXC_CSPI_CLK);
 
-	div = clk_src / max_hz;
+	div = DIV_ROUND_UP(clk_src, max_hz);
 	div = get_cspi_div(div);
 
 	debug("clk %d Hz, div %d, real clk %d Hz\n",

drivers/spi/mxc_spi.c static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs, · line 153

Quoted 8 lines

drivers/spi/mxc_spi.c +1 -1

@@ -147,7 +147,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 	 * The following computation is taken directly from Freescale's code.
 	 */
 	if (clk_src > max_hz) {
-		pre_div = clk_src / max_hz;
+		pre_div = DIV_ROUND_UP(clk_src, max_hz);
 		if (pre_div > 16) {
 			post_div = pre_div / 16;
 			pre_div = 15;

Agree - do you also get a case where the divider was too low and the SPI does not work or it was only examining the code ?

Acked-by Stefano Babic <[email protected]>

Best regards,
Stefano Babic

Signature · 5 lines

=====================================================================
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-53 Fax: +49-8142-66989-80 Email: sbabic at denx.de
=====================================================================

Benoît Thébaudeau

author

2012-08-11 14:23 UTC #3 lore raw

PATCH 1/1 mxc_spi: Round up clock divider

Hi Stefano,

Quoted 40 lines · Stefano Babic

Quoted 6 lines · Beno?t Th?baudeau
Since the input frequency of the API is a maximum that should not be exceeded in
order for the devices to operate properly, the SPI clock divider should be
rounded up, not truncated.
Hi Beno?t,
Quoted 30 lines
Signed-off-by Beno?t Th?baudeau <[email protected]>
Cc Wolfgang Denk <[email protected]>
Cc Stefano Babic <[email protected]>
---
 .../drivers/spi/mxc_spi.c                          |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
(quoted diff) +0 -0
u-boot-4d3c95f/drivers/spi/mxc_spi.c
index 2e15318..cf1462f 100644
drivers/spi/mxc_spi.c +1 -1
@@ -96,7 +96,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave
 *mxcs, unsigned int cs,
 
 	clk_src = mxc_get_clock(MXC_CSPI_CLK);
 
-	div = clk_src / max_hz;
+	div = DIV_ROUND_UP(clk_src, max_hz);
 	div = get_cspi_div(div);
 
drivers/spi/mxc_spi.c +1 -1
 	debug("clk %d Hz, div %d, real clk %d Hz\n",
@@ -147,7 +147,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave
 *mxcs, unsigned int cs,
 	 * The following computation is taken directly from Freescale's
 	 code.
 	 */
 	if (clk_src > max_hz) {
-		pre_div = clk_src / max_hz;
+		pre_div = DIV_ROUND_UP(clk_src, max_hz);

Quoted 8 lines

drivers/spi/mxc_spi.c static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs, · line 153
Quoted 4 lines
drivers/spi/mxc_spi.c +0 -0
 		if (pre_div > 16) {
drivers/spi/mxc_spi.c +0 -0
 			post_div = pre_div / 16;
 			pre_div = 15;
Agree - do you also get a case where the divider was too low and the SPI
does not work or it was only examining the code ?

It was only examining the code. I had many clock issues on i.MX51, so I made a global review of clock usage that led to that. Most i.MX5 clock functions are broken. I have a series fixing these that I will post next week.

Quoted 4 lines

Acked-by Stefano Babic <[email protected]>
Best regards,
Stefano Babic

Best regards,
Beno?t

Stefano Babic

2012-08-20 07:54 UTC #4 lore raw

PATCH 1/1 mxc_spi: Round up clock divider

In reply to Benoît Thébaudeau

Quoted 26 lines · Beno?t Th?baudeau

Since the input frequency of the API is a maximum that should not be exceeded in order for the devices to operate properly, the SPI clock divider should be rounded up, not truncated.
Signed-off-by Beno?t Th?baudeau <[email protected]>
Cc Wolfgang Denk <[email protected]>
Cc Stefano Babic <[email protected]>
---
 .../drivers/spi/mxc_spi.c                          |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
drivers/spi/mxc_spi.c +1 -1
index 2e15318..cf1462f 100644
@@ -96,7 +96,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 
 	clk_src = mxc_get_clock(MXC_CSPI_CLK);
 
-	div = clk_src / max_hz;
+	div = DIV_ROUND_UP(clk_src, max_hz);
 	div = get_cspi_div(div);
 
 	debug("clk %d Hz, div %d, real clk %d Hz\n",

drivers/spi/mxc_spi.c static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs, · line 153

Quoted 8 lines

drivers/spi/mxc_spi.c +1 -1

@@ -147,7 +147,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 	 * The following computation is taken directly from Freescale's code.
 	 */
 	if (clk_src > max_hz) {
-		pre_div = clk_src / max_hz;
+		pre_div = DIV_ROUND_UP(clk_src, max_hz);
 		if (pre_div > 16) {
 			post_div = pre_div / 16;
 			pre_div = 15;

Applied to u-boot-imx, thanks.

Best regards,
Stefano Babic

Signature · 5 lines

=====================================================================
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-53 Fax: +49-8142-66989-80 Email: sbabic at denx.de
=====================================================================