netdev - Re: [PATCH 09/10] stmmac: MDC clock dynamically based on the csr clock input

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Date:	Mon, 02 Apr 2012 13:17:22 +0200
From:	Giuseppe CAVALLARO <peppe.cavallaro@...com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	srinivas.kandagatla@...com, deepak.sikri@...com,
	spear-devel@...t.st.com, shiraz.hashim@...com, viresh.kumar@...com,
	bhutchings@...arflare.com
Subject: Re: [PATCH 09/10] stmmac: MDC clock dynamically based on the csr
 clock input

On 3/23/2012 10:53 AM, David Laight wrote:
>  
> 
>> -----Original Message-----
>> From: netdev-owner@...r.kernel.org 
>> [mailto:netdev-owner@...r.kernel.org] On Behalf Of Giuseppe CAVALLARO
>> Sent: 23 March 2012 09:09
>> To: netdev@...r.kernel.org
>> Cc: davem@...emloft.net; srinivas.kandagatla@...com; 
>> deepak.sikri@...com; spear-devel@...t.st.com; 
>> shiraz.hashim@...com; viresh.kumar@...com; 
>> bhutchings@...arflare.com; Giuseppe Cavallaro
>> Subject: [PATCH 09/10] stmmac: MDC clock dynamically based on 
>> the csr clock input
>>
>> If a specific clk_csr value is passed from the platform
>> this means that the CSR Clock Range selection cannot be
>> changed at run-time and it is fixed (as reported in the driver
>> documentation). Viceversa the driver will try to set the MDC
>> clock dynamically according to the actual clock input.
>>
>> Signed-off-by: Deepak Sikri <deepak.sikri@...com>
>> Reviewed-by: Francesco Virlinzi <francesco.virlinzi@...com>
>> Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@...com>
>> ---
>>  Documentation/networking/stmmac.txt               |    2 +-
>>  drivers/net/ethernet/stmicro/stmmac/common.h      |   10 +++++
>>  drivers/net/ethernet/stmicro/stmmac/stmmac.h      |    1 +
>>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |   40 
>> +++++++++++++++++++++
>>  drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c |    4 +-
>>  5 files changed, 54 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/networking/stmmac.txt 
>> b/Documentation/networking/stmmac.txt
>> index eacb640..ab1e8d7 100644
>> --- a/Documentation/networking/stmmac.txt
>> +++ b/Documentation/networking/stmmac.txt
>> @@ -137,7 +137,7 @@ Where:
>>   o pbl: the Programmable Burst Length is maximum number of beats to
>>         be transferred in one DMA transaction.
>>         GMAC also enables the 4xPBL by default.
>> - o clk_csr: CSR Clock range selection.
>> + o clk_csr: fixed CSR Clock range selection.
>>   o has_gmac: uses the GMAC core.
>>   o enh_desc: if sets the MAC will use the enhanced 
>> descriptor structure.
>>   o tx_coe: core is able to perform the tx csum in HW.
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h 
>> b/drivers/net/ethernet/stmicro/stmmac/common.h
>> index f4df1eb..312e3f1 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/common.h
>> +++ b/drivers/net/ethernet/stmicro/stmmac/common.h
>> @@ -97,6 +97,16 @@ struct stmmac_extra_stats {
>>  	unsigned long normal_irq_n;
>>  };
>>  
>> +/* CSR Frequency Access Defines*/
>> +#define CSR_F_35M	35000000
>> +#define CSR_F_60M	60000000
>> +#define CSR_F_100M	100000000
>> +#define CSR_F_150M	150000000
>> +#define CSR_F_250M	50000000
>> +#define CSR_F_300M	300000000
> 
> The value of CSR_F_250M looks like a typo.

yes you are right, I'll fix it and re-send the all patches.

> These defines look rather pointless to me though!
> 
> Another patch has:
>> -----------------------------------------
>> 	Selection	MDC Clock
>> -----------------------------------------
>> 	1000 		clk_csr_i/4
>> 	1001 		clk_csr_i/6
>> 	1010 		clk_csr_i/8
>> 	1011 		clk_csr_i/10
>> 	1100 		clk_csr_i/12
>> 	1101	 	clk_csr_i/14
>> 	1110 		clk_csr_i/16
>> 	1111 		clk_csr_i/18
> I detect a pattern ...

On this mac, the MDC clock can be set by user in several ways.
if the bit Reg4 bit 5 is 0 so the clock divisor will be driven according
to a fixed range of frq (CSR_F_35M & CO).
If the bit 5 is set then "custom" divisors can be used.
I know it's quite tricky but these patches (from SPEAr) that I reviewed,
indeed, added an useful fix to  dynamically set the MDC clock according
to the actual clock source. This also helped somebody on custom boards.

Peppe

> 
> 	David
> 
> 
> 
> 

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