* [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
@ 2010-10-01 3:03 Philip Rakity
2010-10-05 2:34 ` Chris Ball
0 siblings, 1 reply; 5+ messages in thread
From: Philip Rakity @ 2010-10-01 3:03 UTC (permalink / raw)
To: linux-mmc@vger.kernel.org
>From 8136dcbf78b5f9914caffbedf0ac2bc86426002c Mon Sep 17 00:00:00 2001
From: Philip Rakity <prakity@marvell.com>
Date: Thu, 30 Sep 2010 15:34:24 -0700
Subject: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
The sd 3.0 host spec does not require the clock divider to be a power of 2.
Signed-off-by: Philip Rakity <prakity@marvell.com>
---
drivers/mmc/host/sdhci.c | 8 +++-----
1 files changed, 3 insertions(+), 5 deletions(-)
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 96c7f60..73a94fe 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1003,14 +1003,12 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
goto out;
if (host->version >= SDHCI_SPEC_300) {
- /* Version 3.00 divisors must be a multiple of 2. */
if (host->max_clk <= clock)
div = 1;
else {
- for (div = 2; div < SDHCI_MAX_DIV_SPEC_300; div += 2) {
- if ((host->max_clk / div) <= clock)
- break;
- }
+ div = host->max_clk/clock;
+ if (host->max_clk % clock)
+ div++;
}
} else {
/* Version 2.00 divisors must be a power of 2. */
--
1.6.0.4
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
2010-10-01 3:03 [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider Philip Rakity
@ 2010-10-05 2:34 ` Chris Ball
2010-10-05 17:22 ` Hein_Tibosch
2010-10-06 13:05 ` David Vrabel
0 siblings, 2 replies; 5+ messages in thread
From: Chris Ball @ 2010-10-05 2:34 UTC (permalink / raw)
To: David Vrabel, Philip Rakity; +Cc: linux-mmc@vger.kernel.org
Hi David,
On Thu, Sep 30, 2010 at 08:03:14PM -0700, Philip Rakity wrote:
> From: Philip Rakity <prakity@marvell.com>
> Date: Thu, 30 Sep 2010 15:34:24 -0700
> Subject: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
>
> The sd 3.0 host spec does not require the clock divider to be a power of 2.
>
> Signed-off-by: Philip Rakity <prakity@marvell.com>
> ---
> drivers/mmc/host/sdhci.c | 8 +++-----
> 1 files changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 96c7f60..73a94fe 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1003,14 +1003,12 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
> goto out;
>
> if (host->version >= SDHCI_SPEC_300) {
> - /* Version 3.00 divisors must be a multiple of 2. */
> if (host->max_clk <= clock)
> div = 1;
> else {
> - for (div = 2; div < SDHCI_MAX_DIV_SPEC_300; div += 2) {
> - if ((host->max_clk / div) <= clock)
> - break;
> - }
> + div = host->max_clk/clock;
> + if (host->max_clk % clock)
> + div++;
> }
> } else {
> /* Version 2.00 divisors must be a power of 2. */
> --
Would you mind reviewing this, please? I don't have access to the 3.0
spec.
Thanks very much,
--
Chris Ball <cjb@laptop.org> <http://printf.net/>
One Laptop Per Child
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
2010-10-05 2:34 ` Chris Ball
@ 2010-10-05 17:22 ` Hein_Tibosch
2010-10-06 13:05 ` David Vrabel
1 sibling, 0 replies; 5+ messages in thread
From: Hein_Tibosch @ 2010-10-05 17:22 UTC (permalink / raw)
To: Philip Rakity; +Cc: Chris Ball, David Vrabel, linux-mmc@vger.kernel.org
Hi Philip, Chris,
On 5-10-2010 10:34, Chris Ball wrote:
> Hi David,
>
> On Thu, Sep 30, 2010 at 08:03:14PM -0700, Philip Rakity wrote:
>> From: Philip Rakity <prakity@marvell.com>
>> Date: Thu, 30 Sep 2010 15:34:24 -0700
>> Subject: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
>>
>> The sd 3.0 host spec does not require the clock divider to be a power of 2.
The text and code for sd 3.0 was talking about a multiple of 2, not a power of 2
>> Signed-off-by: Philip Rakity <prakity@marvell.com>
>> ---
>> drivers/mmc/host/sdhci.c | 8 +++-----
>> 1 files changed, 3 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index 96c7f60..73a94fe 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -1003,14 +1003,12 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>> goto out;
>>
>> if (host->version >= SDHCI_SPEC_300) {
>> - /* Version 3.00 divisors must be a multiple of 2. */
>> if (host->max_clk <= clock)
>> div = 1;
>> else {
>> - for (div = 2; div < SDHCI_MAX_DIV_SPEC_300; div += 2) {
>> - if ((host->max_clk / div) <= clock)
>> - break;
>> - }
>> + div = host->max_clk/clock;
>> + if (host->max_clk % clock)
>> + div++;
If you mean to divide and round up, wouldn't :
+ div = DIV_ROUND_UP (host->max_clk, clock);
be nicer and cheaper?
Can SDHCI_MAX_DIV_SPEC_300 be dropped safely?
(don't have access to the sd 3.0 specs neither)
Hein
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
2010-10-05 2:34 ` Chris Ball
2010-10-05 17:22 ` Hein_Tibosch
@ 2010-10-06 13:05 ` David Vrabel
1 sibling, 0 replies; 5+ messages in thread
From: David Vrabel @ 2010-10-06 13:05 UTC (permalink / raw)
To: Chris Ball; +Cc: Philip Rakity, linux-mmc@vger.kernel.org
Chris Ball wrote:
> Hi David,
>
> On Thu, Sep 30, 2010 at 08:03:14PM -0700, Philip Rakity wrote:
>> From: Philip Rakity <prakity@marvell.com>
>> Date: Thu, 30 Sep 2010 15:34:24 -0700
>> Subject: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
>>
>> The sd 3.0 host spec does not require the clock divider to be a power of 2.
>>
>> Signed-off-by: Philip Rakity <prakity@marvell.com>
>> ---
>> drivers/mmc/host/sdhci.c | 8 +++-----
>> 1 files changed, 3 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index 96c7f60..73a94fe 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -1003,14 +1003,12 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>> goto out;
>>
>> if (host->version >= SDHCI_SPEC_300) {
>> - /* Version 3.00 divisors must be a multiple of 2. */
>> if (host->max_clk <= clock)
>> div = 1;
>> else {
>> - for (div = 2; div < SDHCI_MAX_DIV_SPEC_300; div += 2) {
>> - if ((host->max_clk / div) <= clock)
>> - break;
>> - }
>> + div = host->max_clk/clock;
>> + if (host->max_clk % clock)
>> + div++;
>> }
>> } else {
>> /* Version 2.00 divisors must be a power of 2. */
>> --
>
> Would you mind reviewing this, please? I don't have access to the 3.0
> spec.
NAK. The divisors for 3.00 controllers must be a multiple of two (the
register value N gives a divisor of 2N).
David
--
David Vrabel, Senior Software Engineer, Drivers
CSR, Churchill House, Cambridge Business Park, Tel: +44 (0)1223 692562
Cowley Road, Cambridge, CB4 0WZ http://www.csr.com/
Member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
@ 2010-10-05 23:30 Philip Rakity
0 siblings, 0 replies; 5+ messages in thread
From: Philip Rakity @ 2010-10-05 23:30 UTC (permalink / raw)
To: linux-mmc@vger.kernel.org; +Cc: Hein_Tibosch
>
>On 5-10-2010 10:34, Chris Ball wrote:
>> Hi David,
>>
>> On Thu, Sep 30, 2010 at 08:03:14PM -0700, Philip Rakity wrote:
>>> From: Philip Rakity <prakity@marvell.com>
>>> Date: Thu, 30 Sep 2010 15:34:24 -0700
>>> Subject: [PATCH] sdhci: adjust sd 3.0 host controller spec clock divider
>>>
>>> The sd 3.0 host spec does not require the clock divider to be a power of 2.
>
>The text and code for sd 3.0 was talking about a multiple of 2, not a power of 2
>
>>> Signed-off-by: Philip Rakity <prakity@marvell.com>
>>> ---
>>> drivers/mmc/host/sdhci.c | 8 +++-----
>>> 1 files changed, 3 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>> index 96c7f60..73a94fe 100644
>>> --- a/drivers/mmc/host/sdhci.c
>>> +++ b/drivers/mmc/host/sdhci.c
>>> @@ -1003,14 +1003,12 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>>> goto out;
>>>
>>> if (host->version >= SDHCI_SPEC_300) {
>>> - /* Version 3.00 divisors must be a multiple of 2. */
>>> if (host->max_clk <= clock)
>>> div = 1;
>>> else {
>>> - for (div = 2; div < SDHCI_MAX_DIV_SPEC_300; div += 2) {
>>> - if ((host->max_clk / div) <= clock)
>>> - break;
>>> - }
>>> + div = host->max_clk/clock;
>>> + if (host->max_clk % clock)
>>> + div++;
>If you mean to divide and round up, wouldn't :
>
>+ div = DIV_ROUND_UP (host->max_clk, clock);
>
>be nicer and cheaper?
nicer -- yes
cheaper -- code is executed normally to set the clock for f_min and then for max frequency.
>
>Can SDHCI_MAX_DIV_SPEC_300 be dropped safely?
I believe so -- code should not be called from mmc layerwith speed lower then f_min nor more then f_max
>
>(don't have access to the sd 3.0 specs neither)
>
>Hein
>
^ permalink raw reply [flat|nested] 5+ messages in thread
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2010-10-05 2:34 ` Chris Ball
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2010-10-06 13:05 ` David Vrabel
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