linux-kernel - Re: [PATCH 2/2] firmware: arm_scmi: Support 'reg-io-width' property for shared memory

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Message-ID: <6d601728-7f38-400c-9a51-8170d33f0055@broadcom.com>
Date: Sun, 11 Aug 2024 14:03:50 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Peng Fan <peng.fan@....com>,
 "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Sudeep Holla <sudeep.holla@....com>,
 Cristian Marussi <cristian.marussi@....com>,
 "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
 <devicetree@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>,
 "arm-scmi@...r.kernel.org" <arm-scmi@...r.kernel.org>,
 "james.quinlan@...adcom.com" <james.quinlan@...adcom.com>,
 "justin.chen@...adcom.com" <justin.chen@...adcom.com>,
 "kapil.hali@...adcom.com" <kapil.hali@...adcom.com>,
 "bcm-kernel-feedback-list@...adcom.com"
 <bcm-kernel-feedback-list@...adcom.com>
Subject: Re: [PATCH 2/2] firmware: arm_scmi: Support 'reg-io-width' property
 for shared memory



On 8/11/2024 5:42 AM, Peng Fan wrote:
>> Subject: [PATCH 2/2] firmware: arm_scmi: Support 'reg-io-width'
>> property for shared memory
>>
>> Some shared memory areas might only support a certain access width,
>> (e.g.: 32 bits accesses only). Update the shmem layer to support
>> reading from and writing to such shared memory area using the
>> specified I/O width in the Device Tree. The various transport layers
>> making use of the shmem.c code are updated accordingly to pass the
>> I/O width to the routines that need it.
>>
>> Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
>> ---
> 
> [...]
>>   }
>>
>>   static void smc_mark_txdone(struct scmi_chan_info *cinfo, int ret, diff
>> --git a/drivers/firmware/arm_scmi/shmem.c
>> b/drivers/firmware/arm_scmi/shmem.c
>> index 01d8a9398fe8..192262d63baa 100644
>> --- a/drivers/firmware/arm_scmi/shmem.c
>> +++ b/drivers/firmware/arm_scmi/shmem.c
>> @@ -34,9 +34,20 @@ struct scmi_shared_mem {
>>   	u8 msg_payload[];
>>   };
>>
>> +#define __shmem_copy_toio_tpl(s)			\
>> +	for (unsigned int i = 0; i < xfer->tx.len; i += shmem_io_width)
>> 		\
>> +		iowrite##s(((u##s *)(xfer->tx.buf))[i / shmem_io_width],
>> 	\
>> +			   shmem->msg_payload + i);
> 
> there will be a barrier with iowrite, use raw_write##s?

Makes sense, and that matches what memcpy_{from,to}_io() does, too.

> 
>> +
>> +#define __shmem_copy_fromio_tpl(s)			\
>> +	for (unsigned int i = 0; i < xfer->rx.len; i += shmem_io_width)
>> 		\
>> +		((u##s *)(xfer->rx.buf))[i / shmem_io_width] =
>> 		\
>> +			 ioread##s(shmem->msg_payload +
>> shmem_io_width + i);
> 
> Use raw_ioread##s?

Agreed.

-- 
Florian