linux-kernel - Re: [PATCH net-next v2 2/4] net: ipa: use upper_32

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Message-ID: <982ded1e-b8da-d017-16bf-1a0d4bb46246@ieee.org>
Date:   Thu, 18 Mar 2021 11:24:14 -0500
From:   Alex Elder <elder@...e.org>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Alex Elder <elder@...aro.org>, davem@...emloft.net,
        kuba@...nel.org
Cc:     bjorn.andersson@...aro.org, evgreen@...omium.org,
        cpratapa@...eaurora.org, subashab@...eaurora.org, elder@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/4] net: ipa: use upper_32_bits()

On 3/18/21 11:03 AM, Florian Fainelli wrote:
> 
> 
> On 3/18/2021 6:51 AM, Alex Elder wrote:
>> Use upper_32_bits() to extract the high-order 32 bits of a DMA
>> address.  This avoids doing a 32-position shift on a DMA address
>> if it happens not to be 64 bits wide.
>>
>> Suggested-by: Florian Fainelli <f.fainelli@...il.com>
>> Signed-off-by: Alex Elder <elder@...aro.org>
>> ---
>> v2: - Switched to use the existing function, as suggested by Florian.
>>
>>   drivers/net/ipa/gsi.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
>> index 2119367b93ea9..82c5a0d431ee5 100644
>> --- a/drivers/net/ipa/gsi.c
>> +++ b/drivers/net/ipa/gsi.c
>> @@ -711,7 +711,7 @@ static void gsi_evt_ring_program(struct gsi *gsi, u32 evt_ring_id)
>>   	val = evt_ring->ring.addr & GENMASK(31, 0);
> 
> Did you want to introduce another patch to use lower_32_bits() for the
> assignment above?

Bah... Yes, I should have done that.  I was really just
focused on the new function I created and didn't need
to.   I'll do as you suggest.

I'll also see if I do that anywhere else in the driver
and will use these functions as well if appropriate.

I'll do so in the same patch 2 of version 3.

Thanks Florian.

					-Alex

> 
>>   	iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_2_OFFSET(evt_ring_id));
>>   
>> -	val = evt_ring->ring.addr >> 32;
>> +	val = upper_32_bits(evt_ring->ring.addr);
>>   	iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_3_OFFSET(evt_ring_id));
>>   
>>   	/* Enable interrupt moderation by setting the moderation delay */
>> @@ -819,7 +819,7 @@ static void gsi_channel_program(struct gsi_channel *channel, bool doorbell)
>>   	val = channel->tre_ring.addr & GENMASK(31, 0);
> 
> And likewise?
> 
>>   	iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_2_OFFSET(channel_id));
>>   
>> -	val = channel->tre_ring.addr >> 32;
>> +	val = upper_32_bits(channel->tre_ring.addr);
>>   	iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_3_OFFSET(channel_id));
>>   
>>   	/* Command channel gets low weighted round-robin priority */
>>
>