netdev - Re: [PATCH 02/15] ARM: pxa: add dma slave map

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Date:   Tue, 3 Apr 2018 08:51:37 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Robert Jarzmik <robert.jarzmik@...e.fr>
Cc:     Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Tejun Heo <tj@...nel.org>, Vinod Koul <vinod.koul@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Nicolas Pitre <nico@...xnic.net>,
        Samuel Ortiz <samuel@...tiz.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        IDE-ML <linux-ide@...r.kernel.org>, dmaengine@...r.kernel.org,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        Networking <netdev@...r.kernel.org>, devel@...verdev.osuosl.org,
        alsa-devel@...a-project.org
Subject: Re: [PATCH 02/15] ARM: pxa: add dma slave map

On Mon, Apr 2, 2018 at 4:26 PM, Robert Jarzmik <robert.jarzmik@...e.fr> wrote:
> +
> +static const struct dma_slave_map pxa_slave_map[] = {
> +       /* PXA25x, PXA27x and PXA3xx common entries */
> +       { "pxa-pcm-audio", "ac97_mic_mono", PDMA_FILTER_PARAM(LOWEST, 8) },
> +       { "pxa-pcm-audio", "ac97_aux_mono_in", PDMA_FILTER_PARAM(LOWEST, 9) },
> +       { "pxa-pcm-audio", "ac97_aux_mono_out", PDMA_FILTER_PARAM(LOWEST, 10) },
> +       { "pxa-pcm-audio", "ac97_stereo_in", PDMA_FILTER_PARAM(LOWEST, 11) },
> +       { "pxa-pcm-audio", "ac97_stereo_out", PDMA_FILTER_PARAM(LOWEST, 12) },
> +       { "pxa-pcm-audio", "ssp1_rx", PDMA_FILTER_PARAM(LOWEST, 13) },
> +       { "pxa-pcm-audio", "ssp1_tx", PDMA_FILTER_PARAM(LOWEST, 14) },
> +       { "pxa-pcm-audio", "ssp2_rx", PDMA_FILTER_PARAM(LOWEST, 15) },
> +       { "pxa-pcm-audio", "ssp2_tx", PDMA_FILTER_PARAM(LOWEST, 16) },
> +       { "pxa2xx-ir", "rx", PDMA_FILTER_PARAM(LOWEST, 17) },
> +       { "pxa2xx-ir", "tx", PDMA_FILTER_PARAM(LOWEST, 18) },
> +       { "pxa2xx-mci.0", "rx", PDMA_FILTER_PARAM(LOWEST, 21) },
> +       { "pxa2xx-mci.0", "tx", PDMA_FILTER_PARAM(LOWEST, 22) },


> +       { "smc911x.0", "rx", PDMA_FILTER_PARAM(LOWEST, -1) },
> +       { "smc911x.0", "tx", PDMA_FILTER_PARAM(LOWEST, -1) },
> +       { "smc91x.0", "data", PDMA_FILTER_PARAM(LOWEST, -1) },

This one is interesting, as you are dealing with an off-chip device,
and the channel number is '-'1. How does this even work? Does it
mean

> +       /* PXA25x specific map */
> +       { "pxa25x-ssp.0", "rx", PDMA_FILTER_PARAM(LOWEST, 13) },
> +       { "pxa25x-ssp.0", "tx", PDMA_FILTER_PARAM(LOWEST, 14) },
> +       { "pxa25x-nssp.1", "rx", PDMA_FILTER_PARAM(LOWEST, 15) },
> +       { "pxa25x-nssp.1", "tx", PDMA_FILTER_PARAM(LOWEST, 16) },
> +       { "pxa25x-nssp.2", "rx", PDMA_FILTER_PARAM(LOWEST, 23) },
> +       { "pxa25x-nssp.2", "tx", PDMA_FILTER_PARAM(LOWEST, 24) },
> +       { "pxa-pcm-audio", "nssp2_rx", PDMA_FILTER_PARAM(LOWEST, 15) },
> +       { "pxa-pcm-audio", "nssp2_tx", PDMA_FILTER_PARAM(LOWEST, 16) },
> +       { "pxa-pcm-audio", "nssp3_rx", PDMA_FILTER_PARAM(LOWEST, 23) },
> +       { "pxa-pcm-audio", "nssp3_tx", PDMA_FILTER_PARAM(LOWEST, 24) },
> +
> +       /* PXA27x specific map */
> +       { "pxa-pcm-audio", "ssp3_rx", PDMA_FILTER_PARAM(LOWEST, 66) },
> +       { "pxa-pcm-audio", "ssp3_tx", PDMA_FILTER_PARAM(LOWEST, 67) },
> +       { "pxa27x-camera.0", "CI_Y", PDMA_FILTER_PARAM(HIGHEST, 68) },
> +       { "pxa27x-camera.0", "CI_U", PDMA_FILTER_PARAM(HIGHEST, 69) },
> +       { "pxa27x-camera.0", "CI_V", PDMA_FILTER_PARAM(HIGHEST, 70) },
> +
> +       /* PXA3xx specific map */
> +       { "pxa-pcm-audio", "ssp4_rx", PDMA_FILTER_PARAM(LOWEST, 2) },
> +       { "pxa-pcm-audio", "ssp4_tx", PDMA_FILTER_PARAM(LOWEST, 3) },
> +       { "pxa2xx-mci.1", "rx", PDMA_FILTER_PARAM(LOWEST, 93) },
> +       { "pxa2xx-mci.1", "tx", PDMA_FILTER_PARAM(LOWEST, 94) },
> +       { "pxa3xx-nand", "data", PDMA_FILTER_PARAM(LOWEST, 97) },
> +       { "pxa2xx-mci.2", "rx", PDMA_FILTER_PARAM(LOWEST, 100) },
> +       { "pxa2xx-mci.2", "tx", PDMA_FILTER_PARAM(LOWEST, 101) },
> +};

Since more than half the entries in here are chip specific, maybe it would be
better to split that table into three and have a copy for each one in
arch/arm/mach-pxa/pxa{25x.27x.3xx}.c? Does that mean it's actually
a memory-to-memory transfer with a device being on the external
SRAM interface?

       Arnd