linux-kernel - Re: [PATCH 6/7] staging: fsl-mc: rewrite mc command send/receive to work on 32-bits

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Date:   Mon, 17 Jul 2017 14:53:54 +0000
From:   Laurentiu Tudor <laurentiu.tudor@....com>
To:     Robin Murphy <robin.murphy@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "stuyoder@...il.com" <stuyoder@...il.com>
CC:     "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "Ruxandra Ioana Radulescu" <ruxandra.radulescu@....com>,
        "arnd@...db.de" <arnd@...db.de>,
        "marc.zyngier@....com" <marc.zyngier@....com>,
        Roy Pledge <roy.pledge@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "agraf@...e.de" <agraf@...e.de>,
        "Catalin Horghidan" <catalin.horghidan@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Leo Li <leoyang.li@....com>,
        Bharat Bhushan <bharat.bhushan@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 6/7] staging: fsl-mc: rewrite mc command send/receive to
 work on 32-bits

Hi Robin,

On 07/17/2017 04:43 PM, Robin Murphy wrote:
> On 17/07/17 14:26, laurentiu.tudor@....com wrote:
>> From: Laurentiu Tudor <laurentiu.tudor@....com>
>>
>> Split the 64-bit accesses in 32-bit accesses because there's no real
>> constrain in MC to do only atomic 64-bit. There's only one place
>> where ordering is important: when writing the MC command header the
>> first 32-bit part of the header must be written last.
>> We do this switch in order to allow compiling the driver on 32-bit.
>
> #include <linux/io-64-nonatomic-hi-lo.h>
>
> Then you can just use writeq()/writeq_relaxed()/readq_relaxed() on
> 32-bit platforms as well.
>

Thanks, didn't knew of the header. This should take care of the 
compilation errors i was seeing. There's one problem though: these 
handle byte-ordering and i need raw accessors. :-(

---
Best Regards, Laurentiu

>> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
>> ---
>>   drivers/staging/fsl-mc/bus/mc-sys.c | 31 ++++++++++++-------------------
>>   1 file changed, 12 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/staging/fsl-mc/bus/mc-sys.c b/drivers/staging/fsl-mc/bus/mc-sys.c
>> index 195d9f3..dd2828e 100644
>> --- a/drivers/staging/fsl-mc/bus/mc-sys.c
>> +++ b/drivers/staging/fsl-mc/bus/mc-sys.c
>> @@ -124,14 +124,15 @@ static inline void mc_write_command(struct mc_command __iomem *portal,
>>   {
>>   	int i;
>>
>> -	/* copy command parameters into the portal */
>> -	for (i = 0; i < MC_CMD_NUM_OF_PARAMS; i++)
>> -		__raw_writeq(cmd->params[i], &portal->params[i]);
>> -	/* ensure command params are committed before submitting it */
>> -	wmb();
>> -
>> -	/* submit the command by writing the header */
>> -	__raw_writeq(cmd->header, &portal->header);
>> +	/*
>> +	 * copy command parameters into the portal. Final write
>> +	 * triggers the submission of the command.
>> +	 */
>> +	for (i = sizeof(struct mc_command) / sizeof(u32) - 1; i >= 0; i--) {
>> +		__raw_writel(((u32 *)cmd)[i], &((u32 *)portal)[i]);
>> +		/* ensure command params are committed before submitting it */
>> +		wmb();
>> +	}
>>   }
>>
>>   /**
>> @@ -148,19 +149,11 @@ static inline enum mc_cmd_status mc_read_response(struct mc_command __iomem *
>>   						  struct mc_command *resp)
>>   {
>>   	int i;
>> -	enum mc_cmd_status status;
>> -
>> -	/* Copy command response header from MC portal: */
>> -	resp->header = __raw_readq(&portal->header);
>> -	status = mc_cmd_hdr_read_status(resp);
>> -	if (status != MC_CMD_STATUS_OK)
>> -		return status;
>>
>> -	/* Copy command response data from MC portal: */
>> -	for (i = 0; i < MC_CMD_NUM_OF_PARAMS; i++)
>> -		resp->params[i] = __raw_readq(&portal->params[i]);
>> +	for (i = 0; i < sizeof(struct mc_command) / sizeof(u32); i++)
>> +		((u32 *)resp)[i] = __raw_readl(&((u32 *)portal)[i]);
>>
>> -	return status;
>> +	return mc_cmd_hdr_read_status(resp);
>>   }
>>
>>   /**
>>
>