From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH v2] dmaengine: tegra-apb: proper default init of channel slave_id Date: Fri, 22 Apr 2016 15:40:10 +0100 Message-ID: <571A37CA.5080001@nvidia.com> References: <1461329093-20300-1-git-send-email-smohammed@nvidia.com> <571A2819.9000507@nvidia.com> <36d59e91fa72417d94ae2672e423ebb4@bgmail102.nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <36d59e91fa72417d94ae2672e423ebb4-7W72rfoJkVlxWE4FnwvcdlaTQe2KTcn/@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Shardar Mohammed , Laxman Dewangan , "vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org" , "dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org" , "swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org" , "thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" , "gnurou-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" , "dmaengine-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-tegra@vger.kernel.org On 22/04/16 14:56, Shardar Mohammed wrote: > Thanks for the review, please check my comments inline in [Shardar]. > >> On 22/04/16 13:44, Shardar Shariff Md wrote: >>> Initialize default channel slave_id(req_sel) to invalid id (i.e max >>> supported slave id + 1) to avoid overwriting of slave_id during >>> tegra_dma_slave_config() with client data if slave_id is not >>> initialized through DT >>> >>> Signed-off-by: Shardar Shariff Md >>> >>> --- >>> - Instead of initializing the slave id to -1 define macros for >>> max slave id and invalid slave id and do the checks accordingly. >>> --- >>> drivers/dma/tegra20-apb-dma.c | 13 +++++++++++-- >>> 1 file changed, 11 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/dma/tegra20-apb-dma.c >>> b/drivers/dma/tegra20-apb-dma.c index 3871f29..2957e26 100644 >>> --- a/drivers/dma/tegra20-apb-dma.c >>> +++ b/drivers/dma/tegra20-apb-dma.c >>> @@ -114,6 +114,9 @@ >>> /* Channel base address offset from APBDMA base address */ >>> #define TEGRA_APBDMA_CHANNEL_BASE_ADD_OFFSET 0x1000 >>> >>> +#define TEGRA_APBDMA_SLAVE_ID_MAX 31 >> >> Sorry, thinking about this some more, given that the ID is programmed into a >> field in the CSR register could we just define as mask here for the CSR field ... >> >> #define TEGRA_APBDMA_CSR_REQ_SEL_MASK 0x1f >> >> Note this should be defined with the other CSR register field definitions. > [Shardar] Will take care of it. One doubt do you mean below. > Will define this with other CSR register fields. > #define TEGRA_APBDMA_CSR_REQ_SEL_MASK 0x1f > > #define TEGRA_APBDMA_SLAVE_ID_MAX TEGRA_APBDMA_CSR_REQ_SEL_MASK We don't need the MAX definition as well. >> >>> +#define TEGRA_APBDMA_SLAVE_ID_INVALID >> (TEGRA_APBDMA_SLAVE_ID_MAX + 1) >>> >>> struct tegra_dma; >>> >>> /* >>> @@ -353,7 +356,7 @@ static int tegra_dma_slave_config(struct dma_chan >> *dc, >>> } >>> >>> memcpy(&tdc->dma_sconfig, sconfig, sizeof(*sconfig)); >>> - if (!tdc->slave_id) >>> + if (tdc->slave_id == TEGRA_APBDMA_SLAVE_ID_INVALID) >>> tdc->slave_id = sconfig->slave_id; >> >> I believe I mentioned before that here we should ... >> >> if (tdc->slave_id != TEGRA_APBDMA_SLAVE_ID_INVALID) >> return -EBUSY; > > [Shardar] By the time this function tegra_dma_slave_config is called, slave_id here is already initialized through DT(provided option) through function tegra_dma_of_xlate(). > And filling up the slave id here from sconfig structure that is provided by dma client driver is used here if it dma client is not initialized through DT. > Please correct me if am wrong. Yes you are right. So on further inspection this allows the user to set the slave ID if it is not set yet. So I think we need ... if (tdc->slave_id == TEGRA_APBDMA_SLAVE_ID_INVALID) { if (sconfig->slave_id > TEGRA_APBDMA_CSR_REQ_SEL_MASK) return -EINVAL; else tdc->slave_id = sconfig->slave_id; } Cheers Jon