Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
In-Reply-To: <20180622104930.32050-8-boris.brezillon@bootlin.com>
References: <20180622104930.32050-1-boris.brezillon@bootlin.com> <20180622104930.32050-8-boris.brezillon@bootlin.com>
From:   Arnd Bergmann <arnd@arndb.de>
Date:   Wed, 11 Jul 2018 16:19:51 +0200
Message-ID: <CAK8P3a1D_crzMT8-2R9bMvMuq8F58=BgHUFSq2nntRHF0sZUQg@mail.gmail.com>
Subject: Re: [PATCH v5 07/10] i3c: master: Add driver for Cadence IP
To:     Boris Brezillon <boris.brezillon@bootlin.com>
Cc:     Wolfram Sang <wsa@the-dreams.de>, linux-i2c@vger.kernel.org,
        Jonathan Corbet <corbet@lwn.net>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Przemyslaw Sroka <psroka@cadence.com>,
        Arkadiusz Golec <agolec@cadence.com>,
        Alan Douglas <adouglas@cadence.com>,
        Bartosz Folta <bfolta@cadence.com>,
        Damian Kos <dkos@cadence.com>,
        Alicja Jurasik-Urbaniak <alicja@cadence.com>,
        Cyprian Wronka <cwronka@cadence.com>,
        Suresh Punnoose <sureshp@cadence.com>,
        Rafal Ciepiela <rafalc@cadence.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Nishanth Menon <nm@ti.com>, Rob Herring <robh+dt@kernel.org>,
        Pawel Moll <pawel.moll@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>,
        DTML <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Vitor Soares <Vitor.Soares@synopsys.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Xiang Lin <Xiang.Lin@synaptics.com>,
        linux-gpio@vger.kernel.org, Sekhar Nori <nsekhar@ti.com>,
        Przemyslaw Gaj <pgaj@cadence.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Jun 22, 2018 at 12:49 PM, Boris Brezillon
<boris.brezillon@bootlin.com> wrote:
> Add a driver for Cadence I3C master IP.

The driver seems very well-written and shows that the framework got that side
of the interface right. Just one thing I noticed:

> +
> +static void cdns_i3c_master_handle_ibi(struct cdns_i3c_master *master,
> +                                      u32 ibir)

> +
> +       for (i = 0; i < IBIR_XFER_BYTES(ibir); i += 4) {
> +               u32 tmp = readl(master->regs + IBI_DATA_FIFO);
> +
> +               for (j = 0; j < 4 && i + j < dev->ibi->max_payload_len; j++)
> +                       buf[i + j] = tmp >> (j * 8);
> +       }

This seems to be a rather inefficient way to open-code a readsl().
I suppose you need to handle length that is not a multiple of 4, right?

Maybe do it like

      size_t length = IBIR_XFER_BYTES(ibir);
      readsl(master->regs + IBI_DATA_FIFO, buf, length & ~3);
      if (length & 3) {
            u32 tmp = __raw_readl(master->regs + IBI_DATA_FIFO);
            memcpy(buf + length & ~3, length & 3);
      }

     Arnd