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Mon, 20 Jan 2020 06:42:54 -0600 Received: from [192.168.2.6] (ileax41-snat.itg.ti.com [10.172.224.153]) by lelv0326.itg.ti.com (8.15.2/8.15.2) with ESMTP id 00KCgqNv125311; Mon, 20 Jan 2020 06:42:53 -0600 Subject: Re: [PATCH] media: rcar_drif: Use dma_request_chan() instead dma_request_slave_channel() To: Geert Uytterhoeven CC: Mauro Carvalho Chehab , Ramesh Shanmugasundaram , Vinod , Linux Media Mailing List , Linux Kernel Mailing List , Linux-Renesas References: <20191217104025.23318-1-peter.ujfalusi@ti.com> From: Peter Ujfalusi Message-ID: Date: Mon, 20 Jan 2020 14:43:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20/01/2020 14.36, Geert Uytterhoeven wrote: > Hi Peter, > > On Mon, Jan 20, 2020 at 1:09 PM Peter Ujfalusi wrote: >> On 20/01/2020 14.05, Geert Uytterhoeven wrote: >>> On Tue, Dec 17, 2019 at 11:41 AM Peter Ujfalusi wrote: >>>> dma_request_slave_channel() is a wrapper on top of dma_request_chan() >>>> eating up the error code. >>>> >>>> By using dma_request_chan() directly the driver can support deferred >>>> probing against DMA. >>>> >>>> Signed-off-by: Peter Ujfalusi >>> >>> Reviewed-by: Geert Uytterhoeven >>> >>> One comment below. >>> >>>> --- a/drivers/media/platform/rcar_drif.c >>>> +++ b/drivers/media/platform/rcar_drif.c >>>> @@ -275,10 +275,10 @@ static int rcar_drif_alloc_dmachannels(struct rcar_drif_sdr *sdr) >>>> for_each_rcar_drif_channel(i, &sdr->cur_ch_mask) { >>>> struct rcar_drif *ch = sdr->ch[i]; >>>> >>>> - ch->dmach = dma_request_slave_channel(&ch->pdev->dev, "rx"); >>>> - if (!ch->dmach) { >>>> + ch->dmach = dma_request_chan(&ch->pdev->dev, "rx"); >>>> + if (IS_ERR(ch->dmach)) { >>>> rdrif_err(sdr, "ch%u: dma channel req failed\n", i); >>> >>> Now there is an error code, you might (1) want to print it, and (2) only >>> do so when it is not due to probe deferral: >>> >>> if (PTR_ERR(ch->dmach) != -EPROBE_DEFER) >>> rdrif_err(sdr, "ch%u: dma channel req failed %pe\n", >>> i, ch->dmach); >> >> Yes, this is true. >> >>> >>>> - ret = -ENODEV; >>>> + ret = PTR_ERR(ch->dmach); >> >> if (ret != -EPROBE_DEFER) >> rdrif_err(sdr, "ch%u: dma channel req failed (%d)\n", i, ret); >> >> might be simpler. > > Sure, checking ret is simpler. > But printing ch->dmach means you can use the new %pe format specifier > to pretty-print the error code. Ah, I was not aware of this, but there is another issue with the patch: I need to set the ch->dmach to NULL before jumping to dmach_error.. I'll send v3 in a minute. > > Gr{oetje,eeting}s, > > Geert > - Péter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki